AACGEDr. EdithLawrencedbourre AACG TDr. DaviPhilips Ldave.van ConferenDr. Sean Sandia Nsjhearn@ ProgramDr. Luis Lawrenczepedaru Prof. DavUniversitdavid@e StanfordNancy HSales & M530-541-

E-West Presih Bourret-Coe Berkeley Nt@lbl.gov

Treasurer: d Vanderwa

Lumileds Lignderwater@p

nce Chair: J. Hearne

National Labo@sandia.gov

m Chairs: A. Zepeda-Re Livermore

uiz1@llnl.go

vid Kisailus ty of Califor

engr.ucr.edu

d Serra CamHarrison

Marketing D-1244

ident/ Locaourchesne National Lab

ater ghting Compphilips.com

oratory

Ruiz e National Lav

rnia Riversid

mp Contact:

Director

l Arrangem

bs

pany

aboratory

de

:

ments Chair::

Sunday, 6/3/2012

Stanford Lounge 3:00 PM - 5:30 PM Check-In/Registration

Dining Room 5:30 PM - 7:00 PM Dinner

7:00 PM - 8:00 PM Plenary I

8:00 PM - 8:40 PM Fundamentals of Materials Growth I

Monday, 6/4/2012

Dining Room 7:30 AM- 9:00AM Breakfast

9:00 AM - 10:40 AM Biomaterials Growth and Processes I

10:40 AM - 11:10 AM Coffee

11:10 AM - 12:10 PM Biomaterials Growth and Processes II

Dining Room 12:10 PM - 1:30 PM Lunch

1:30 PM - 3:00 PM Unscheduled time

3:00 PM - 4:30 PM Poster Session I

4:30 PM - 6:00 PM Poster Session II

Old Lodge Deck 4:30 PM - 6:00 PM Wine Social

Dining Room 6:00 PM - 7:30 PM Dinner

7:30 PM - 8:50 PM Biomaterials Growth and Processes III

8:50 PM - 9:50 PM Energy Materials Growth and Applications I

Cathedral Room

Angora Room

Cathedral Room

Cathedral Room

Tuesday, 6/5/2012

Dining Room 7:30 AM- 9:00AM Breakfast

9:00 AM - 10:40 AM Energy Materials Growth and Applications III

10:40 AM - 11:10 AM Coffee

11:10 AM - 12:10 PM Energy Materials Growth and Applications IV

Dining Room 12:10 PM - 1:30 PM Lunch

1:30 PM - 6:00 PM Unscheduled time

Dining Room 6:00 PM - 7:30 PM Banquet

7:30 PM - 8:50 PM Energy Materials Growth and Applications V

8:50 PM - 9:50 PM Fundamentals of Materials Growth II

Wednesday, 6/6/2012

Dining Room 7:30 AM- 9:00AM Breakfast

9:00 AM - 10:40 AM Fundamentals of Materials Growth III

10:40 AM - 11:10 AM Coffee

11:10 AM - 12:10 PM Fundamentals of Materials Growth IV

Dining Room 12:10 PM - 1:30 PM Lunch

Cathedral Room

Cathedral Room

Main Hall

Sunday, 6/3/2012 Speaker Title

3:00 PM 7:00 PM

7:00 PM 8:00 PM Linda SapochakThe Good, the Bad and the Beautiful: The Relevance of Crystalline Material Research to Advancing Materials Discovery and Development

8:00 PM 8:40 PM Hanchen Huang A framework of nano crystal growth

Monday, 6/4/2012 Speaker Title

7:30 AM 9:00 AM

9:00 AM 9:40 AM Janet Moradian-OldakCooperative action of tooth enamel proteins amelogenin and enamelin in controlling mineralization

9:40 AM 10:00 AM Andrzej WierzbickiSingle-Molecule-Level Investigation of Interactions between Collagen and Hydroxyapatite

10:00 AM 10:20 AM Paul SmeetsPre-Nucleation Species in Calcium Carbonate Solution Precipitation: Clusters or Complexes?

10:20 AM 10:40 AM Adam WallaceVanishing nucleation barrier results in appearance of an ion-rich liquid-like phase prior to CaCO3 crystallization

10:40 AM 11:10 AM

11:10 AM 11:50 AM Peter Vekilov The Physical Chemistry of Sickle Cell Anemia

11:50 AM 12:10 PM Kang Rae ChoIncorporation of block copolymer micelles into calcite single crystals investigated by in situ atomic force microscopy

12:10 PM 7:30 PM

7:30 PM 8:10 PM William LandisModeling Mineral Nucleation in Type I Collagen of Vertebrate Tissues

8:10 PM 8:50 PM Jim De YoreoPhysical insights into protein matrix self-assembly and mineralization

8:50 PM 9:10 PM Nichola KinsingerBiologically Inspired Synthesis of a Photocatalytically Active Membrane for Water Treatment

9:10 PM 9:30 PM Eric SamulonGrowth and study of undoped and europium doped BaBrCl scintillator crystals: Impact of oxygen defects on performance

9:30 PM 9:50 PM Qiyin LinVapor Growth and Chemical Delithiation of Stoichiometric LiCoO2 Single Crystals

Lunch - Free Time - Posters - Wine Social - Dinner

Check-In/Registration - Dinner

Breakfast

Coffee

Tuesday, 6/5/2012 Speaker Title

7:30 AM 9:00 AM

9:00 AM 9:40 AM Howard KatzInterfacial morphology and thin film order in organic semiconductor devices

9:40 AM 10:20 AM John SullivanMaterials Challenges in Electrical Energy Storage: Phase Transformations, Reaction Mechanisms, and Degradation in Li-ion Batteries

10:20 AM 10:40 AM Yang LiuIn-situ TEM observations of the operation of a single nanowire electrode in a lithium ion battery

10:40 AM 11:10 AM

11:10 AM 11:50 AM Joshua KuntzColloidal Crystal Assembly by Electrophoretic Deposition – Experiments and Modeling

11:50 AM 12:10 PM Pierre-Yves PichonInfluence of nucleation conditions on RGS (Ribbon growth on substrate) crystal morphology

12:10 PM 7:30 PM

7:30 PM 8:10 PM James SpeckProgress in Nonpolar and Semipolar GaN Materials and Devices

8:10 PM 8:30 PM Peter SchunemannAll-epitaxial growth of orientation-patterned gallium phosphide (OPGaP) for mid-IR laser applications

8:30 PM 8:50 PM Patrick CappillinoGrowth of Nanoporous Palladium and Palladium Alloys in Soft Templates for High Power Density Hydrogen Storage

8:50 PM 9:30 PM Moneesh UpmanyuInterfacial energetics and morphology during growth of gold-catalyzed silicon nanowires

9:30 PM 9:50 PM Dongsheng LiDirection-specific interactions control crystal growth by oriented attachment

Wednesday, 6/6/2012 Speaker Title

7:30 AM 9:00 AM

9:00 AM 9:40 AM Jonah Erlebacher Growth and Design of Nanoporous Nanoparticle Catalysts

9:40 AM 10:00 AM David RobinsonElectroless Atomic Layer Deposition: a Scalable Approach to Tailored Surface Structures

10:00 AM 10:20 AM Ray SehgalOnset of crystallization in assemblies of colloidal nanoparticles

10:20 AM 10:40 AM Jeffrey DerbyUnderstanding the Fundamental Challenges for Improving the Growth of CZT Crystals for Radiation Detectors

10:40 AM 11:10 AM

11:10 AM 11:50 AM Bruce ClemonsNucleation Control in Atomic Layer Deposition and Hydrogen Storage Reactions

11:50 AM 12:10 PM Tammy OlsonOne-dimensional Nanostructures: Growth Mechanism, Assembly Manipulation, and Materials Applications

12:10 PM

Coffee

Conference End - Sack lunch available

Breakfast

Breakfast

Lunch - Free Time - Banquet

Coffee

Session ChRoom: CaSunday, (J

Start Ti7:00 PM

hairs: Hearathedral RooJune 03) 19:

ime TM

TRAD

rne, Sean: Som :00 - 20:00

Title The Good, thRelevance oAdvancing MDevelopmen

Sandia Natio

he Bad and tof CrystallineMaterials Dint

onal Labora

the Beautifue Material Riscovery and

atories

ul: The Research to d

Authors Sapochak, etal.

Durration60

Abstract Details:

Session: Date: Time: Room:

Plenary 06/03 19:00 Main hall

Title: The Good, the Bad and the Beautiful: The Relevance of Crystalline Material Research to Advancing Materials Discovery and Development Authors: Sapochak, Linda 1 1National Science Foundation

Abstract: Linda S. Sapochak, Program Director, Solid State and Materials Chemistry, Division of Materials Research, National Science Foundation

Control of the crystalline structure of a material largely dictates its physical properties. While crystal growth of several technologically important materials – quartz, silicon, germanium, potassium dihydrogen phosphate - has been nearly perfected over the past five decades, crystal growth research itself has lagged in the U.S. The urgency of the issue was addressed in a 2009 National Research Council report, Frontiers in Crystalline Matter – From Discovery to Technology. The report stressed, “Discovery of new crystalline materials and growth of single crystals have been shown continually to be highly leveraged activities, yielding disproportionately large returns on investment while helping address important national issues related to energy, information, transportation, national security, health, and other areas.” While there has not been a wide-spread response by federal funding agencies to specifically address this problem, crystalline material discovery and crystal growth research should be a crucial component of the national Materials Genome Initiative (MGI), which aims to shorten the material development cycle in the US. In response to this initiative, the NSF supports an activity entitled Designing Materials to Revolutionize and Engineer our Future (DMREF). DMREF is spearheaded jointly by the Mathematical and Physical Sciences (MPS) and Engineering (ENG) Directorates, and funds transformative approaches that seek to accelerate materials discovery and commercialization and to advance fundamental materials understanding in such a way that material properties can be predicted, optimized, and ultimately controlled through design. This presentation will show current work supported by the NSF in crystalline material research spanning many programs and material classes and discuss how this type of fundamental research is relevant to future funding opportunities at the NSF.

Session ChRoom: CaSunday, (J

Start Ti8:00 PM

hairs: Zepedathedral RooJune 03) 20:

ime TM A

da-Ruiz, Luom :00 - 20:40

Title A framewor

uis: Lawren

k of nano cr

nce Livermo

rystal growth

ore National

h

l Laborator

Authors Huang, etal

ries

Durl.

ration40

Abstract Details:

Session: Date: Time: Room:

Fundamentals of Materials Growth 06/03 20:00 Main hall

Title: A framework of nano crystal growth

Authors: Huang, Hanchen 1

1University of Connecticut

Abstract: Crystal growth on solid has been a focus of research since 1950s. However, the growth of crystalline nanostructures on solid, being a part of the nano fashion, has defied the established theory of crystal growth and has gone on without a systematic theory. Recently, the speaker and his associates have developed a framework of nano crystal growth, using a combination of atomistic simulations, analytical formulations, and physical vapor deposition experiments. This framework builds on three advancements of crystal growth principles: (1) the surface diffusion over steps sensitively depends on step thickness; (2) multiple-layer steps can be kinetically stabilized, in contrast to the classical theory of Schwoebel and Shipsey (1966); and (3) a characteristic length scale develops from the coupling of diffusion kinetics and kinetic stability of multiple-layer steps.

Session CRoom: CMonday

Start Tim9:00 AM

9:40 AM

10:00 AM

10:20 AM

Chairs: OrCathedral Ry, (June 04)

me TitM Co

ammin

M Sinbet

M PreSol

M Vaan cry

me, Chris: Room

09:00 - 10:4

tle operative ac

melogenin andneralization

ngle-Molecutween Collag

e-Nucleationlution Precip

nishing nuclion-rich liqu

ystallization

Lawrence L

40

ction of toothd enamelin i

ule-Level Invgen and Hyd

n Species in Cpitation: Clu

leation barriuid-like phas

Livermore N

h enamel proin controlling

vestigation odroxyapatite

Calcium Carusters or Com

er results in se prior to C

National La

oteins g

of Interaction

rbonate mplexes?

appearance aCO3

aboratory

AuthorMoradiOldak,

ns Wierzbetal.

Smeetsetal.

of Wallacetal.

rs Duraian-etal.

bicki,

s,

e,

ation 40

20

20

20

Abstract Details:

Session: Date: Time: Room: Biomaterials Growth and Processes 06/04 9:00 Main hall Title: Cooperative action of tooth enamel proteins amelogenin and enamelin in controlling mineralization Authors: Moradian-Oldak, Janet 1 1University of Sothern California Abstract: Amelogenin is the major protein component of the developing enamel extracellular matrix that together with non-amelogenins control the nucleation and organized growth of dental enamel crystals. We sought to examine the hypothetical cooperative role of the acidic enamelin and the relatively hydrophobic amelogenin in controlling the growth morphology of enamel crystals in the post-secretory stage of enamel formation. We first investigated the interactions between enamelin and amelogenin by applying biophysical methods (Eur J Oral Sci. 2011;119:351-6., J Struct Biol. 2009 Apr;166(1):88-94.Cells Tissues Organs, 2011;194-198). We then examined the effect of these proteins on the morphology of octacalcium phopsphate crystals (OCP) grown in a cation selective membrane system in a 10% (w/v) recombinant porcine amelogenin (rP148) with and without the 32kDa enamelin fragment (Cryst Growth Des. 2010 Nov;10(11):4815-4822). DLS analysis of amelogenin/enamelin mixture (molar ratio 10:1) at pH 6.5 showed that the hydrodynamic radii (RH) of amelogenin particles increased in average from 9.3±1 to 12.3±1.4nm following the addition of enamelin. At pH 7.4, addition of enamelin resulted in the dispersion of amelogenin aggregation decreasing sizes from 674±67.4 to 356.9 ± 48nm. At pH 7.4 and at molar ratio of 10:1, oligomers of 4.5±0.1nm constituted 78% of the particle mass. The blue shift of emission maximum in the fluorescence spectra and changes in intensity minima in CD spectra were indicative of conformational changes in amelogenin following their interactions with enamelin. Enamelin alone inhibited the growth in the c-axis direction more than amelogenin, yielding OCP crystals with the smallest aspect ratio of all conditions tested. When enamelin was added to the amelogenin “gel-like matrix”, the inhibitory action of the protein mixture on the growth of OCP in the c-axis direction was diminished, while that in the b-axis direction was increased. As a result, the length to width ratio (aspect ratio) of OCP crystal was markedly increased. Addition of enamelin to amelogenin enhanced the potential of amelogenin to stabilize the amorphous calcium phosphate (ACP) transient phase. The ratio of enamelin and amelogenin was crucial for stabilization of ACP and the growth of OCP crystals with larger aspect ratio. The cooperative regulatory action of enamelin and amelogenin was attained, presumably, through co-assembling of enamelin and amelogenin. These results have important implications in understanding the growth mechanism of enamel crystals with large aspect ratio.

Abstract Details: Session: Date: Time: Room: Biomaterials Growth and Processes 06/04 9:40 Main hall Title: Single-Molecule-Level Investigation of Interactions between Collagen and Hydroxyapatite Authors: Wierzbicki, Andrzej 1; Battle, Keith 1; Tao, Jinhui 2; Salter, Alan 1; De Yoreo, Jim 2 1University of South Alabama , 2Lawrence Berkeley National Laboratory Abstract: In this study we have investigated the interactions between a triple helix of collagen and the (100) and (110) faces of hydroxyapatite (HAP). Using NAMD and the CHARMM force field, we have employed constant velocity Steered Molecular Dynamics (cv-SMD) simulations, which allowed us to better understand the large-scale interactions between collagen and HAP. We have used the simulation results to calculate the binding affinities and preferred orientations of interaction of collagen on the (100) and (110) faces of HAP, and we have compared our results with the findings of atomic force microscopy and single-molecule atomic force spectroscopy. Additionally, we have studied collagen-collagen interactions on the surface of HAP. Implications of our findings for the understanding of biogenically nucleated and grown crystals of HAP will be discussed.

Abstract Details: Session: Date: Time: Room: Biomaterials Growth and Processes 06/04 10:00 Main hall Title: Pre-Nucleation Species in Calcium Carbonate Solution Precipitation: Clusters or Complexes? Authors: Smeets, Paul J.M. 1; Habraken, Wouter J.E.M. 2; Nudelman, Fabio 1; Sommerdijk, Nico A.J.M. 1 1Eindhoven University of Technology , 2Max Planck Institute of Colloids and Interfaces Abstract: Calcium carbonate is the most abundant biogenic mineral, found in geological deposits, marine organisms and is used in various industrial applications. Despite its relevance, a fundamental understanding of the evolution of its crystalline forms is still under debate, in particular since recent reports on non-classical crystallization pathways. In the present study, the existence of stable 0.4-0.6nm calcium carbonate (CaC) clusters in calcium carbonate mineralization is demonstrated. For this we used cryo-TEM in combination with a titration set-up, where a dilute calcium source was added to a dilute carbonate/bicarbonate buffer over time, at constant pH and temperature. In contrast to the previously proposed neutral CaCO3 clusters, in the present case the chemistry of the CaCO3-cluster is determined to have a Ca/C ratio <<1 and to contain at least 50 mol% of bicarbonate. Such a composition implies that the clusters would have a negative charge, which is indeed confirmed by zeta-potential measurements in this work. Furthermore, it is shown that their formation in the pre-nucleation stage can only be due to a binding behavior of one calcium in the equilibrium structure, which indicates that they behave as complexes in solution. We further demonstrate that amorphous sub-micron sized assemblies of these complexes exist already before the nucleation event, and act as a precursor to the vaterite polymorph. We propose a mechanism that explains the transition from CaC complexes via this intermediate aggregate state into the final calcium carbonate polymorph.

Abstract Details: Session: Date: Time: Room: Biomaterials Growth and Processes 06/04 10:20 Main hall Title: Vanishing nucleation barrier results in appearance of an ion-rich liquid-like phase prior to CaCO3 crystallization Authors: Wallace, Adam 1; DeYoreo, James 2; Banfield, Jillian 3 1Lawrence Berkeley Laboratory , 2Molecular Foundry, Lawrence Berkeley Laboratory , 3Department of Earth & Planetary Science, UC Berkeley Abstract: Recent experimental characterizations of the early stages of calcium carbonate crystallization reveal an abundance of nanometer-sized “pre-nucleation” clusters that appear prior to the formation of an amorphous intermediate phase. The interpretation of the clusters as thermodynamically stable species is not easily reconcilable with long-standing solution speciation models with demonstrated predictive capability near equilibrium. Further, the presence of the clusters has been used as an indicator of the non-classical nature of the crystallization pathway; however, these observations are not at odds with the classical expectation that metastable clusters should appear as thermally-driven fluctuations in solution drive them to form against sizable thermodynamic barriers opposing nucleation. The existence of transient phases and cluster species has significant implications for carbonate nucleation and growth in natural and engineered environments, both modern and ancient. The structure of these intermediate phases remains elusive, as does the nature of the disorder to order transition, however, these process details may strongly influence the interpretation of elemental and isotopic climate proxy data obtained from authigenic and biogenic carbonates. Molecular simulations are potentially valuable for investigating the early stages of crystallization. However, in practice their application to nucleation is inhibited by the presence of kinetic traps that prevent adequate sampling of the energy landscape within timescales typically accessible by simulation. This research addresses this challenge by advancing the use of replica-exchange molecular dynamics (REMD) techniques to accelerate the exploration of energy landscapes. REMD has been used previously to enhance sampling of protein conformations that occupy energy wells that are separated by significant thermodynamic and kinetic barriers, and is used here to probe the initial formation and onset of order within hydrated calcium carbonate cluster species. A two-phase thermodynamic model is also used to determine the free energy of the neutral clusters as a function of size and to enable comparison with classical nucleation theory. The results of the free energy calculations suggest that the carbonate mineral clusters form spontaneously from solution, unopposed by a thermodynamic barrier at conditions relevant to biomineralization. Further, there is no indication that certain particle sizes are preferred within the 0.2 – 2 nm size range investigated. Calculated ion diffusivities indicate that the clusters maintain liquid-like character into the nano-size regime, suggesting that crystallization occurs within the ion-rich phase.

Session CRoom: CMonday

Start Tim11:10 AM

11:50 AM

Chairs: OrCathedral Ry, (June 04)

me TitleM

The Anem

M

Incorinto situ a

me, Chris: Room

11:10 - 12:1

e Physical Chmia

rporation of calcite singlatomic force

Lawrence L

10

hemistry of S

f block copole crystals in

e microscopy

Livermore N

Sickle Cell

lymer micellnvestigated by

National La

AutVeketal

les by in Cho

aboratory

thors kilov , l.

o, etal.

Duration40

20

Abstract Details: Session: Date: Time: Room: Biomaterials Growth and Processes 06/04 11:10 Main hall Title: The Physical Chemistry of Sickle Cell Anemia Authors: Vekilov , Peter 1 1University of Houston Abstract: Sickle cell anemia is a deadly inherited disease. Every year, about 500,000 children are born with this disease, mostly in the poorest countries of equatorial Africa and the inland regions of India. The sickle cell gene leads to the expression of a mutant hemoglobin, HbS, which induces two main pathological sequences: (i) HbS forms polymers which stretch and rigidify the erythrocytes. (ii) HbS is unstable to autoxidation and hence to release of its hemes. The released heme oxidizes to hematin, which, among other pathological consequences, is known to damages the erythrocyte membranes, and enhance their adhesion to the endothelial walls. Both of these sequences lead to blood flow obstruction, organ damage, and death. We study the interactions between the two consequences of the sickle cell gene. We show that the concentration of free heme in HbS solutions typically used in the laboratory is 0.02 – 0.05 mole heme/mole HbS. We show that dialysis of small molecules out of HbS arrests HbS polymerization. The addition of 100 – 260 uM of free heme to dialyzed HbS solutions leads to rates of nucleation and polymer fiber growth faster by two orders of magnitude than prior to dialysis. Towards an understanding of the mechanism of nucleation enhancement by heme, we show that free increases by two orders of magnitude the volume of the metastable clusters of dense HbS liquid, the locations where HbS polymer nuclei form. These results suggest that free heme in the erythrocytes of sickle cell anemia patients may be a major factor for the puzzling complexity of the clinical manifestations of sickle cell anemia. The prevention of free heme accumulation in the erythrocyte cytosol may be a novel avenue to sickle cell therapy.

Abstract Details: Session: Date: Time: Room: Biomaterials Growth and Processes 06/04 11:50 Main hall Title: Incorporation of block copolymer micelles into calcite single crystals investigated by in situ atomic force microscopy Authors: Cho, Kang Rae 1; Kim, Yi-Yeoun 2; Pan, Haihua 1; Lau, Jolene 1; Yang, Pengcheng 3; Hu, Qiaona 1; Wang, Debin 1; Friddle, Raymond 4; Kulshreshtha, Prashant 1; Armes, Steven 3; Meldrum, Fiona 2; De Yoreo, James 1 1Lawrence Berkeley National Laboratory , 2University of Leeds , 3University of Sheffield , 4Sandia National Laboratories Abstract: Macromolecules are often incorporated into single crystals of biominerals and, in this way, their mechanical properties are greatly enhanced. For example, proteins and cellular tissue networks are incorporated within sea urchin spines and plates, which are made of calcite single crystals, improving their fracture toughness. Mimicking biominerals, synthetic calcite single crystals with incorporated carboxylated block copolymer (PSPMA30-PDPA47) micelles showed higher hardness than pure calcite single crystals. To determine the micelle incorporation mechanism at the near molecular level and subsequently gain insight into the more general process of incorporation of biomacromolecules into biogenic minerals, we used in situ AFM to observe micelle incorporation into growing calcite single crystals. We found that micelles directly adsorbed from solution to steps and observed no micelle adsorption to the terraces. Steps showed little or no inhibition by the adsorbed micelles and compressed the micelles causing them to be elongated perpendicular to the growing face. While the micelles were encapsulated into the calcite single crystal by the continual passage of steps, incorporation was accompanied by the formation of cavities at the locations where the micelles were incorporated. In this way, a calcite-micelle single crystal composite was formed. The extent of micelle incorporation into the crystals increased with supersaturation, simply due to the increase in step density with supersaturation. Companion experiments on mica surfaces showed that the negatively charged micelles formed at the high pH of the growth experiments did not adsorb to negative (bare) mica, but adsorbed to positive (polylysine-treated) mica. This suggests that the calcite step along with the solution-calcium ions play a key role in establishing electrostatic adhesion of the micelles to the steps.

Room: AMonday

PosterNumb

1

2

3

4

5

6

7

8

Angora Rooy, (June 04)

r ber

PerioxSbxT

Synthbismu

Frequtransf

An EMech

ZeoliPure

SolvoNano

Textu

InterfFilms

m 16:30 - 18:0

dic ModulatTe3 Multilaye

hesis, consoluth telluride

uency-depenfer in erbium

lectron Backhanism of Or

te Thin FilmSilicalite-1 b

othermal Synostructured C

ure of Pyrite

facial Alloy s

00

T

tion of Sb Sters using Pu

lidation and nanoparticle

ndent dielectrm-doped TlG

kscatter Studriented 001

ms: Titaniumby Secondar

nthesis and CCathodes for

Thin Films

Hydride Des

Title

toichiometryulsed Electro

thermoelectres

ric permittivGaSe2 crystal

dy of the Cry Anatase

m Doped Silicry Growth

Controlled GLithium Ion

by EBSD

stabilization

y in Bi2Te3/Bodeposition

tric propertie

vity and charls

ystal Growth

calite-1 (TS-

Growth of Lin Batteries

n in Mg/Pd T

A

Bi2- Ro

es of Ro

rge Met

h Sa

-1) and Re

iFePO4 Zh

M

Thin CH

uthors

obinson, eta

obinson, eta

Mustafaeva, al.

anchez, etal.

eaves, etal.

hu, etal.

Mars, etal.

HUNG, etal

al.

al.

Abstract Details:

Session: Date: Time: Room:

Poster Session 06/04 16:30 Poster Room

Title: Periodic Modulation of Sb Stoichiometry in Bi2Te3/Bi2-xSbxTe3 Multilayers using Pulsed Electrodeposition Authors: Robinson, David B. 1; Banga, Dhego 1; Lensch-Falk, Jessica L. 1; Medlin, Douglas L. 1; Stavila, Vitalie 1; Yang, Nancy Y. 1; Sharma, Peter A. 1 1Sandia National Laboratories

Abstract: Thin film Bi2Te3/Sb2Te3 multilayers are thought to possess a high thermoelectric figure of merit. Our work describes how multilayers can be fabricated using electrodeposition, an inexpensive and scalable synthetic route. We address the challenge of simultaneously maintaining satisfactory stoichiometry, crystallinity, and scalability for this complex structure. We have synthesized Bi2Te3/Bi2-xSbxTe3 multilayers by pulsed potentiostatic electrodeposition from single baths of acidic aqueous electrolyte, and with a flow cell, over a cm2-scale area. Cyclic voltammetry of the Bi/Sb/Te bath revealed two distinct potentials that resulted in the deposition of Bi2Te3 and (Bi1-xSbx)2Te3. Scanning transmission electron microscopy of the multilayers shows layer periodicity in the 10-30 nm range. Grazing incidence X-ray diffraction measurements show the multilayer films possessed a 015 texture across the entire cm2 substrate. Proper choice of pulse parameters can significantly improve the stoichiometry, crystallography and microstructure of the films. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Abstract Details:

Session: Date: Time: Room:

Poster Session 06/04 16:30 Poster Room

Title: Synthesis, consolidation and thermoelectric properties of bismuth telluride nanoparticles Authors: Robinson, David B. 1; Stavila, Vitalie 1; Hekmaty, Michelle A. 1; Medlin, Douglas L. 1; Banga, Dhego 1; Zhu, Song 2; Tritt, Terry M. 2 1Sandia National Laboratories , 2Clemson University

Abstract: Low-dimensional nanoscale materials are promising as a way to increase the thermoelectric (TE) figure of merit ZT relative to bulk materials. Nanostructured bismuth telluride and its alloys are considered among the most promising TE materials due to their unique band structure and carrier scattering properties. Key to the successful use of such nanostructures in TE devices is the ability to control their band structure, morphology, and grain boundaries. We report an effective method to synthesize bulk amounts of bismuth telluride nanoparticles (NPs) by a low-temperature reaction of bismuth(III) oleate and trioctylphosphine-tellurium in the presence of various organic surfactants and solvents. The conditions of the reactions were optimized to generate stoichiometric, crystalline Bi2Te3 nanoparticles with tunable particle sizes. The structure and morphology of the NPs were investigated by X-ray diffraction, small angle X-ray scattering, infra-red spectroscopy, thermogravimetry, scanning and transmission electron microscopy, and energy dispersive spectroscopy. We utilized an efficient method to strip the surfactants from the surface of the as-synthesized nanomaterials. The NP powders were consolidated using spark plasma sintering (SPS) to generate high-density pellets. We measured the thermoelectric properties of the SPS-consolidated NPs and determined that both the electrical conductivity and Seebeck coefficient of the surfactant-free NPs are higher compared to the corresponding values in surfactant-coated NPs.

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Abstract Details:

Session: Date: Time: Room:

Poster Session 06/04 16:30 Poster Room

Title: Frequency-dependent dielectric permittivity and charge transfer in erbium-doped TlGaSe2 crystals

Authors: Mustafaeva, Solmaz 1 1Institute of Physics NASA Abstract: The purpose of this work was to study the effect of partial Er substitution for Ga on the ac electric and dielectric properties of TlGaSe2 single crystals. Homogenous samples of TlGaSe2 crystals at an Er content of 0.1, 0.5 and 1.0 mol.% were synthesized directly from the initial components. Crystals of the TlGaSe2 compounds were crystallized in monoclinic structure. The crystal date for these crystals are following: a = 10.744; b = 10.773; c = 15.623 Å; b = 100.04°; z =16; V = 178.59 Å3; d = 6.446 g/cm3.

Investigated samples formed flat capacitors whose plane was perpendicular to the crystalline C-axis. Ohmic contacts of samples are made by Ag paste.Measurements of the dielectric coefficients of studied crystals were performed at fixed frequencies by the resonant method. The electrical properties (loss tangent, real and imaginary parts of complex dielectric permittivity, and ac conductivity across the layers of TlGaSe2 layered single crystals doped by Er have been studied in the frequency range f = 50 kHz to 35 MHz. The results demonstrate that the dielectric dispersion in erbium - doped TlGaSe2 crystals has a relaxation nature. Partial substitution of Er for Ga in TlGaSe2 reduces the dielectric permittivity and conductivity. Over the frequency range from 3.2 MHz to 35 MHz in TlGaSe2 crystals doped by Er the hopping conduction through localized states near the Fermi level takes place. We evaluated the Fermi-level density of states NF = (1.2–7.5) × 1018 eV–1cm–3. According to the hopping conduction theory, the average ac hopping length is determined: R = (184–240) Å.

We evaluated the mean hop time of charge carriers between localized states in the band gap of TlGaSe2: τ = 4.4 × 10-8–1.2 ×10–6 s and the energy spread of localized states ΔE near the Fermi level: ΔE = 5 ×10-3–6.4 ×10-2 eV.

Abstract Details:

Session: Date: Time: Room:

Poster Session 06/04 16:30 Poster Room

Title: An Electron Backscatter Study of the Crystal Growth Mechanism of Oriented 001 Anatase Authors: Sanchez, Matt 1; Hayzelden, Clive 1; Ichimura, Andrew 1 1San Francisco State University

Abstract: Titanium dioxide films find applications in photodegradation of contaminants, dye sensitized solar cells (DSSC), and hydrogren production.1 Recently, Yang et al. has synthesized anatase (TiO2) powders with the high energy 001 facets preferentially exposed.2 In our work, we have synthesized oriented anatase thin films with ~100% (001) exposed facets that also show [001] preferred orientation.3 Synthesis of the films was accomplished by controlling the crystal morphology during growth by the addition of a capping agent. Flourine binds to the 101 and 001 facets but lowers the surface energy of the minority 001 surface relative to the 101. Thus the crystal grows istropically along the [100] and [010] zone axes leading to highly truncated bipyramid morphologies whose surfaces are dominated by the 001 facets. It is believed that the growth of the films is a two-step process that involves polymerization followed by a competitive growth mechanism after nucleation on the surface. In this experiment we will study the proposed competitive growth mechanism of the synthesized films via electron backscatter diffraction (EBSD). This is accomplished by taking a film ~600nm thick and using a vibratory polisher to sequentially polish and thin the film to a thickness of (550 nm, 400 nm, 200 nm, 50 nm). At each thickness we study the crystal orientation via EBSD. Such a study will give insight as how the orientation of the film changes over time during the synthesis and the crystal growth mechanism.

1. Baddour-Hadjean, R.;; Pereira-Ramos, J-.P. Chem. Rev. 2010, 110, 1278-1319.

2. Yang, H.; Sun, C. H.; Qiao, S. Z.; Zou, J.; Liu, G.; Smith, S. C.; Cheng, H. M.; Lu, G. Q. Nature 2008, 453, 638-641.

3. Ichimura, A. S.; Mack, B.; Usmani, S.M.; Mars, D. Chem. Mater., 2012, submitted.

Abstract Details:

Session: Date: Time: Room:

Poster Session 06/04 16:30 Poster Room

Title: Zeolite Thin Films: Titanium Doped Silicalite-1 (TS-1) and Pure Silicalite-1 by Secondary Growth Authors: Reaves, Chris 1 1San Francisco State University

Abstract: Thin films of pure silica (silicalite-1) and titanium doped (TS-1) zeolite MFI were synthesized on seeded glass substrates. Pure silica seed crystals of two sizes, 80nm and 200nm, were used and their effect on secondary growth compared. All synthesis gels used for secondary growth contain fluoride and use the same structure directing agent (Tetrapropylammonium fluoride, TPA-F) and silica source (Tetraethyl orthosilicate, TEOS). Such gel compositions inhibit nucleation in the bulk such that, over the relatively short synthesis times employed, the bulk gel remained amorphous and nearly all crystallization occurred on seeded glass substrates. Resultant film growth mirrored seed layer orientation, which was random for the 80nm seeds and highly 'b' oriented for the 200nm seed crystals. Removal of the structure directing agent was carried out by UV/ozone under heat. Seed layers and resulting continuous films were characterized using gXRD and SEM. Organic structure directing agent removal was confirmed by optical spectroscopy. Attempts at Electron Backscatter Detection (EBSD) will be shown but this technique is problematic for zeolite films due to radiation damage during analysis. The purpose of this study was to refine efficient techniques for the synthesis of thin zeolite films to use as low-k dielectrics, membranes for water/gas purification (especially TS-1 films under UV irradiation), and as novel sensors.

Abstract Details:

Session: Date: Time: Room:

Poster Session 06/04 16:30 Poster Room

Title: Solvothermal Synthesis and Controlled Growth of LiFePO4 Nanostructured Cathodes for Lithium Ion Batteries

Authors: Zhu, Jianxin 1; Fiore, Joseph 2; Lu, Richard 2; Lira, Anthony 3; Wang, Qianqian 2; Kinsinger, Nichola 2; Hou , Wenting 2; Kisailus, David 2

1University of California-Riverside, Material Science and Engineering, Riverside, California 92521, United States , 2University of California-Riverside, Department of Chemical and Environmental Engineering, Riverside, California 92521, United States , 3University of California-Riverside, Department of Bioengineering, Riverside, California 92521, United States

Abstract: There have been significant improvements in the Lithium-ion battery technology versus alternatives such as NiCd (Nickel-Cadmium) or NiMH (Nickel-Metal Hydride) cells since Lithium-ion provides higher voltages and larger power densities. Inspired by biology, which uses careful control of local solution chemistry as well as organics, we have developed novel solution methods to produce nanostructured LiFePO4 (LFP) cathodes. By utilizing a solvothermal method, modification of solvent and pH promotes the formation of LFP nanostructures with controlled size, monodispersity, and morphology. Crystal phase and growth behavior were monitored by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), while particle morphologies were observed by Scanning and Transmission Electron Microscopy. The crystal growth mechanisms during the synthesis were interpreted based on time studies under controlled conditions in conjunction with synchrotron analyses. In doing this, we have developed an understanding of the underlying fundamentals controlling habit formation of LFP nanostructures and will be able to determine how these various morphologies affect their behavior in Li-ion batteries. The information revealed by this study will help develop guidelines to control the size and morphological features more precisely, and will help create design strategies for cathodes that will enable efficient lithium ion transport and extended lifetime batteries.

Abstract Details:

Session: Date: Time: Room:

Poster Session 06/04 16:30 Poster Room

Title: Texture of Pyrite Thin Films by EBSD

Authors: Mars, Diana San Francisco State University Abstract: The pyrite phase of iron disulfide holds promise as an inexpensive material for photovoltaics because of its low band gap (0.95 eV) and the abundance of raw materials. However, a low open circuit voltage (0.15-0.2 V) in most natural and synthetic samples poses a challenge for industrial applications.1 It is believed that the density of defect states that arise from sulfur vacancies is so high that they comprise an effective band in stoichiometric FeS2.2 In our work, we would like to synthesize uniform continuous pyrite films from solution with as close as possible stoichiometry. In this study we will examine the texture and crystal growth patterns of polished pyrite films by electron backscatter diffraction (EBSD) and how that correlates to information from x-ray diffraction (XRD), energy dispersive spectroscopy (EDS), UV-Vis spectroscopy and scanning electron microscopy (SEM). Two hydrothermal syntheses are compared to prepare pyrite thin films. The first method uses an aqueous mixture of ferrous sulfate (FeSO4•7H2O), sulfur, and sodium thiosulfate (Na2S2O3) that are mixed Parr reactor and held at 230 °C for 24 hours.3 The second method starts with the preparation of an iron(III) and sulfur containing precursor that decomposes under high temperature and pressure aqueous conditions to yield pyrite nanocrystals.3 Gold on silicon substrates were chosen because of the affinity of sulfide for the gold surface. Substrates were prepared by evaporating 5 nm of Cr and 200 nm of Au onto piranha cleaned silicon (100) wafers. To prepare pyrite films, the substrates were held vertically in the Parr reactor and immersed in the synthesis solution. Pyrite films grown by the two methods both yield densely packed continuous polycrystalline films. However, the single precursor route has the advantage of a more uniform grain size. Films were polished with a vibratory polisher and studied by SEM, EDS, and EBSD. Preliminary results suggest low sulfur percentages for both methods and a higher ratio of pyrite to marcasite phases present in the precursor method.

Abstract Details:

Session: Date: Time: Room:

Poster Session 06/04 16:30 Poster Room

Title: Interfacial Alloy Hydride Destabilization in Mg/Pd Thin Films

Authors: CHUNG, CHIA-JUNG 1; Lee, Sang Chul 1; Groves, James 1; Brower, Edwin 1; Sinclair, Robert 1; Clemens, Bruce 1 1Stanford University Abstract: Magnesium hydride is an attractive hydrogen storage material due to its high hydrogen storage capacity of 7.6%. However, slow kinetics and low equilibrium pressure at room temperature remain difficulties in practical applications. Recently, a remarkable increase in equilibrium hydrogen pressure has been reported for Mg thin films capped with a palladium layer. We show that the increase of equilibrium hydrogen pressure is caused by interfacial alloying destabilization of Mg/Pd alloy, instead of strain energy associated with volume expansion of magnesium hydride formation as reported. In-situ stress measurement was used to directly measure the stress involved during hydrogenation in the thin films. The results show that the observed stress contribute to a negligible amount of increase in equilibrium pressure as we predicted. Transmission electron microscopy and depth profiling x-ray photoemission spectroscopy display the evidence of intermixing between the Mg and Pd interface. Besides, equilibrium hydrogen pressure is further increased in annealed Mg/Pd thin films. Furthermore, a thermodynamic model is proposed to show the effect of alloying on equilibrium hydrogen pressure, which is proportional to the thickness of Mg/Pd alloying region and is about a few nanometers as discovered by transmission electron microscopy.

Room: ATuesday

PosterNumb

Funda

1

2

3

4

5

Energ

6

Poster

7

Angora Rooy, (June 05)

r ber

amentals of

StrucZrSe3

Massgrowt

BackGerm

Studycrysta

Laserdama

gy Materials

Operafor So

r Session

Fluoriin the

m 16:30 - 18:0

Materials G

tural charact3 and ZrS3 c

increment fth in quasi-tw

-diffusion inmanium-Silic

y of effect ofals of barium

r chemical vaged optical

s Growth an

ating Dynamolar Silicon

ide concentre synthesis of

00

Growth

terization ancrystals.

for unsteady wo-dimensio

n the Axial Hcon crystals.

f different pam iodate, mo

apor depositsurfaces

nd Applicati

mics of the H

ration dependf (001) orien

Title

nd transport p

ammonium onal capillar

Heat Process

arameters ononohydrate g

tion of silica

ions

Horizontal Ri

dence of monted anatase

properties of

m chloride denry.

sing (AHP) g

n the growthgrown in silic

a for in-fillin

ibbon Growt

orphology anthin films

f CVT grow

ndrite

grown

h of single ca gel

ng of

th Process

nd orientatio

Authors

wn Dasadia, etal.

Terentiev,etal.

Balikci, etal.

Shitole, etal.

Elhadj, etal.

Derby, etal.

on Mack, etal.

,

Abstract Details: Session: Date: Time: Room: Fundamentals of Materials Growth 06/05 16:30 Poster Room Title: Structural characterization and transport properties of CVT grown ZrSe3 and ZrS3 crystals. Authors: Dasadia, Abhay 1; Nariya, Brinda 1; Jani, Ashvinkumar 1 1Sardar Patel University Abstract: AbstractSingle crystals of ZrSe3 and ZrS3 are family of materials with low symmetry structure were grown by chemical vapour transport technique using iodine as a transporting agent. The grown crystals were characterized by energy dispersive analysis of X-ray (EDAX) for confirmation of stochiometric proportion of constituent elements and structure of grown crystals was determined by X-ray diffraction (XRD) technique. The resistivity and thermoelectric power measurements were carried out in the temperature range 308 K to 573 K. The Hall coefficient, carrier concentration and Hall mobility were determined from Hall Effect measurements at room temperature.

Abstract Details: Session: Date: Time: Room: Fundamentals of Materials Growth 06/05 16:30 Poster Room Title: Mass increment for unsteady ammonium chloride dendrite growth in quasi-two-dimensional capillary. Authors: Terentiev, Pavel 1; Martyushev, Leonid 1 1Ural Federal University Abstract: Unsteady growth of ammonium chloride dendrites during crystallization from an aqueous solution is experimentally investigated. The prepared NH4Cl solution under saturation temperature of 35°C was placed between two glasses with thickness between them not exceeding 0.05 mm. Crystal area S was measured in the triangle sectors with different angles and oriented along various dendrite branches. The measurements were performed during free crystal growth until supersaturation is reduced to zero. The dependency of the normalized crystal area increment (directly proportional to the crystal mass increment) S′(t)/S(t) on the time t was nondimentionalized to one-parameter dependence a(1/t˜-1). Herein t˜ is dimensionless time defined as t˜=t/t* where t* is time of the crystal growth termination. Factor a is equal 1.7±0.2 for all observed sectors and presumably associated only with physical and chemical characteristics of the crystallized system. This result shows universality of unsteady growth of dendrite brunches.

Abstract Details: Session: Date: Time: Room: Fundamentals of Materials Growth 06/05 16:30 Poster Room Title: Back-diffusion in the Axial Heat Processing (AHP) grown Germanium-Silicon crystals. Authors: BALIKCI, ERCAN 1 1BOGAZICI UNIVERSITY Abstract: Researchers and growers of single crystals would be delighted to predict outcomes of a growth process in advance. Axial Heat Processing (AHP) technique, a recent bulk crystal growth method, has been employed by several investigators with a wide range of objectives. The AHP technique mimics the floating zone (FZ) melting. The technique is also known as the Submerged Heater Method (SHM). Researchers and crystal growers often use the equations developed for FZ to predict the outcomes of the AHP method. However, the fact that the charge is solid in FZ and melt in AHP causes significant differences in the solute redistribution, since back-diffusion may exist from the growth region to the charge in AHP. As a result, the match between the experimental outcomes of AHP and the theoretical expressions is often not good. Therefore, a new approach for the solute redistribution and morphological stability in the AHP method is undertaken. Existence of the back-diffusion has been analyzed in this study, and a new model has been developed for the solute redistribution. The analysis of the solute redistribution has been extended to predict the morphological stability in the grown crystals. The new approach for the solute redistribution and the morphological stability has been verified using germanium-silicon crystals grown by the AHP method with different combinations of pulling rates, initial concentrations, and initial melt heights. For the morphological stability, a comparison is made between the constitutional supercooling (CS), Mullins and Sekerka’s perturbation theory (MS), and the theory developed in this current study. Predictions of the new model are superior to those of CS and MS criteria.

Abstract Details: Session: Date: Time: Room: Fundamentals of Materials Growth 06/05 16:30 Poster Room Title: Study of effect of different parameters on the growth of single crystals of barium iodate, monohydrate grown in silica gel Authors: Shitole, Sharda 1 1Z. B. Patil College, Dhule, India Abstract: Single crystals of barium iodate, monohydrate [Ba(IO3)2, H2O] ,which exhibit prominent nonlinear optical property, were grown by gel method. It is a promising technique for growing single crystals of substances, which are sparingly soluble in water and decompose before their melting point. The effect of various parameters like gel density, pH of gel, gel aging, concentration of reactants, and concentration programming was studied.As the gel density increases, transparency of the gel decreases and requires less settling time. Well-defined and transparent single crystals were obtained with sodium meta silicate density 1.04 gm/cc. Below 1.04 gm/cc density, gel took longer time to set and was unstable.The pH of gel was varied from 2 to 6. As pH of gel increases, its transparency decreases. It also decreases the number of nuclei at the time of growth. Grown crystals were opaque and not well defined. With smaller pH values, gel takes longer time to set, is unstable, and can be easily fractured at the time of addition of supernatant. The pH of 4.2 is the optimum value for obtaining good quality crystals.The nucleation density decreases as the aging increases. Insufficient gel aging leads to the formation of fragile gel. It often breaks at the time of addition of supernatant. Aging of 120 hours was found to be most suitable.As the concentration of the feed solution increases, the nucleation density increases. Suitable concentrations of reactants incorporated in gel are found to be 0.05 M and 0.1 M for the feed solution. Change in the position of reactants does not affect either the quality or number of nucleation centers. When the reactants are very dilute, very few nuclei are formed. On increasing the concentration of feed solution, number of nucleation centers was found to increase rather than the growth of already existing nuclei. Thus concentration programming is not helpful for reducing the nucleation density, for increasing the size and for improving the quality of crystals.Thus, the steady state of concentration gradient favors well-developed and perfect crystals, away from the gel interface, where prismatic (2 x 2 x 1.5 mm3) and prismatic pyramidal (3 x 2 x 2 mm3) crystals are obtained.. However, very slow rate of growth along one direction results in the platy crystals. Fast growth rate in one particular direction leads to the formation of elongated crystals like dendrites (10 to 20 x 1 mm2) near the gel interface.

Abstract Details:

Session: Date: Time: Room: Fundamentals of Materials Growth 06/05 16:30 Poster Room Title: Laser chemical vapor deposition of silica for in-filling of damaged optical surfaces Authors: Elhadj, Selim 1; Matthews, Manyalibo 1; Gabe, Guss 1; David, Flores 1; Isaac, Bass 1; Norm, Nielsen 1 1LLNL Abstract: We describe a method to locally deposit silica on silica optical surfaces. The laser chemical vapor deposition method uses a precursor gas tetraorthosilicate (TEOS) flow under atmospheric conditions. A CO2 laser operating between 9 and 11 microns locally heats the absorbing surfaces under controlled precursor chemical flow and composition to achieve a thermally activated polymerization process to form silica. Adjustment of laser power, beam size, exposure time, oxidizer content, and precursor vapor pressure are used to optimize precursor decomposition kinetics and material transport such that the desired microstructure, material properties and morphology are achieved. Localized deposition of material is used to replanarize damaged surfaces where material is missing (e.g. pits, cracks). This study describes how deposited material may be optimized in terms of residual stress, optical form factor and damage threshold by tuning the reactive vapor components and/or laser parameters (power, beam size, pulse/repetition rates, etc.,). Generally, microstructures commensurate with the length scale of the laser beam diameter may be written along surfaces with varying functionality based on the starting chemical precursor. The decomposition of the precursor may be photolytic or pyrolytic, though in pyrolytic mode very high rates of deposition may be achieved at atmospheric pressure due to a finite heat-diffused boundary layer that facilitates gas phase reactions (as well as surface reactions). Oxidizers such as ozone or oxygen can also enhance the process and final composition of the material deposited. The application of such method promises to reduce processing costs, time, and increase durability of laser optics used in high power applications such as nuclear fusion-class lasers. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Abstract Details: Session: Date: Time: Room: Energy Materials Growth and Applications 06/05 16:30 Poster Room

Title: Operating Dynamics of the Horizontal Ribbon Growth Process for Solar Silicon

Authors: Daggolu, Parthiv 1; Yeckel, Andrew 1; Bleil, Carl 2; Derby, Jeffrey 1 1University of Minnesota , 2Ribbon Technology International

Abstract: Several decades of research on terrestrial photovoltaic (PV) technology has resulted in many competing technologies and significant expansions of markets. However, over 90% of annual solar cell production in 2010 was based on crystalline silicon wafers, and the most likely scenario is that silicon technology will continue to dominate commercial production for the next decade and possibly longer.

A significant portion, approximately 70%, of the costs of silicon solar cells is due to substrate wafers. For continued development of this PV technology, silicon crystals must be produced at lower cost and higher quality, and advances in crystal growth processes are needed. The horizontal ribbon growth (HRG) process is a promising technology toward achieving these objectives. This fascinating process was first conceived by Shockley in late 1950's for silicon growth and was practiced by Bleil on the late 1960's for germanium growth. Subsequent large-scale development efforts were carried out by Kudo in Japan in the late 1970's and by the Energy Materials Corporation in the US in the early 1980's. However, after encouraging early results, experimental advances and process development efforts stalled, and this technique was abandoned in favor of more traditional methods that were easier to develop.

Unlike vertical meniscus-defined crystal growth processes, which are inherently stable, there are many failure modes that must be avoided in the HRG process. We argue that its successful operation will rely on a thorough understanding of system design and control--issues that are perhaps only feasibly addressed via computational modeling of the system. Towards these ends, we present a comprehensive, thermal-capillary model based on finite-element methods to study the coupled phenomena of heat transfer, fluid mechanics, and interfacial phenomena (solidification and capillarity) in the HRG process. Bifurcation analysis and transient computations using this model reveal process limitations consistent with known failure modes and suggests operating windows that may allow for stable process operation.

__________________________________________________________________ Supported in part by NSF CBET-075503, the content of which does not necessarily reflect the position or policy of the United States Government, and no official endorsement should be inferred.

Abstract Details: Session: Date: Time: Room: Poster Session 06/05 16:30 Poster Room Title: Fluoride concentration dependence of morphology and orientation in the synthesis of (001) oriented anatase thin films Authors: Mack, Brianne M. 1; Ichimura, Dr. Andrew 1 1San Francisco State University Abstract: Titanium dioxide is a wide band-gap semiconductor with strong absorption in the UV region. Used commercially as a pigment and for UV protection in sunscreen, major research efforts have demonstrated many energy and environmental applications of TiO2, as well as developed a myriad of synthetic methods to obtain TiO2 materials that are variable in phase, morphology, and particle size1. 001 facet-dominated anatase phase TiO2 crystals exhibit superior capabilities in photocatalytic degradation of organic pollutants, solar-hydrogen production, and Li-ion batteries2. Having exploited the recognized role of fluoride in directing anatase crystal growth to synthesize supported films exhibiting a dominant polycrystalline 001 surface and a strong c-axis preferred orientation, our previous work has shown that a number of different fluoride sources (NaF, LiF, CsF, NH4F, N(Et)4F, HF) can be used as crystallographic controlling agents to obtain such films3. In this study, anatase films exhibiting ~100% (001) reactive facets at the surface were grown hydrothermally on gold substrate from homogeneous solutions of TiF4 and NH4F. In order to understand anatase film growth as a function of fluoride concentration, the NH4F concentration was varied from 0 to 200 mM while holding the TiF4 concentration constant at 50 mM. The solutions were placed in Parr bomb Teflon liners with gold substrate, made by evaporating first a wetting layer of Cr, then 200 nm of gold, onto polished Si wafers. The resulting polycrystalline anatase films are continuous, range from 0.2-1.0 μm thick, and evenly coat the substrate. For films made with 0-75 mM NH4F, top-down SEM images show overlapping square crystals with grain sizes from 200 nm to 800 nm. The 100 mM NH4F film exhibits polygonal, roughly textured grains ~500 nm across, while the 200 mM NH4F film exhibits ~800 nm globular mounds coated with a film of ~10 nm spheres. Grazing angle XRD measurements show that the films exhibit a high degree of preferred orientation with the c-axis normal to the substrate surface. Edge-on SEM images reveal that the grains span the thickness of the films. Annealing the films at 500 oC removes fluorine and causes crystallites within the grains to restructure as shown by SEM, XRD, and Raman spectroscopy. Supported anatase films grown from this one-pot method may serve as oxidative photocatalysts and electrodes for photoelectrochemical applications.

Session ChRoom: CaMonday, (

Start Tim7:30 PM

8:10 PM

hairs: Ormathedral Roo(June 04) 19

me TM

MC

M

Pa

me, Chris: Laom 9:30 - 20:50

Title Modeling MCollagen of

Physical insiassembly an

awrence Liv

Mineral NucleVertebrate T

ights into prnd mineraliza

vermore Na

eation in TypTissues

otein matrixation

ational Labo

Ape I

x self-

oratory

Authors Landis, etal.

De Yoreo, etal.

Duration40

40

Abstract Details: Session: Date: Time: Room: Biomaterials Growth and Processes 06/04 19:30 Main hall Title: Modeling Mineral Nucleation in Type I Collagen of Vertebrate Tissues Authors: Landis, William 1 1University of Akron Abstract: The positions of charged residues in the primary amino acid sequence comprising the molecular model of human type I collagen have been investigated utilizing several critical papers concerning collagen structure [1-5]. In the quasi-hexagonal microfibrillar model of collagen assembly and molecular packing in three dimensions, the sites of glutamic and aspartic acid, lysine and arginine, and hydroxylysine and histidine of human type I collagen are notable in a number of features, including (a) the same amino acid appears adjacent in each of the three collagen helices of a single collagen molecule, (b) different amino acids but all of the same charge are adjacent in the three helices, (c) glutamic and/or aspartic acid residues are found close to other glutamic and/or aspartic acid residues along the three helices (and similarly for lysine and/or arginine) and (d) sites with residues of one charge are close to sites with residues of opposite charge [6]. Modeling the charged amino acids along the known type I collagen hole zones [2] reconstructed tomographically as channels or gaps traversing collagen molecular arrays [5] suggests that they may define locations binding calcium and phosphate ions [6]. Molecular dynamics studies of the stereochemical configuration of the charged amino acid side chains indicate side chain orientation toward the channels. The putative binding sites described by side chains of charged residues could serve as direct mineral nucleation centers from which apatite crystals grow and develop. From these results, type I collagen provides an intrafibrillar molecular framework for apatite formation without non-collagenous molecules in extracellular matrices of human and other vertebrate mineralizing tissues. Mineralization between type I collagen species (interfibrillar networks) likely involves both collagen and other molecules. References: [1] J.A. Chapman and R.A. Hardcastle, Connect. Tissue Res. 2, 151-159 (1974). [2] A.J. Hodge and J.A. Petruska, in Aspects of Protein Structure, G.N. Ramachandran (ed.), pp. 289–300, New York, Academic Press (1963). [3] J.P.R.O. Orgel, A. Miller, T.C. Irving, R.F. Fischetti, A.P. Hammersley and T.J. Wess, Structure 9, 1061-1069 (2001). [4] J.P.R.O. Orgel, T.C. Irving, A. Miller and T.J. Wess, Proc. Natl. Acad. Sci. U.S.A. 103, 9001-9005 (2006). [5] W.J. Landis, M.J. Song, A. Leith, L. McEwen, and B. McEwen, J. Struct. Biol. 110, 39–54 (1993). [6] F.H. Silver and W.J. Landis, Connect. Tissue Res. 52, 242-252 (2011).

Abstract Details: Session: Date: Time: Room: Biomaterials Growth and Processes 06/04 20:10 Main hall Title: Physical insights into protein matrix self-assembly and mineralization Authors: De Yoreo, Jim 1 1Lawrence Berkeley National Laboratory Abstract: Self-assembly of protein matrices and subsequent mineralization is a widespread paradigm in biology. The architecture of the underlying matrix imposes order on the nucleating mineral phase. The resulting structural complexity and mechanical properties are unparalleled in current synthetic approaches. Moreover, the vast amount of carbonate mineralization carried out by marine organisms impacts global seawater chemistry and maintains the largest terrestrial reservoir of CO2. Thus matrix assembly and mineralization impact human health and the environment, and are an inspiration to materials scientists. To understand the underlying physical controls governing matrix assembly and mineralization, we have investigated these processes using in situ AFM and optical microscopy combined with dynamic force spectroscopy(DFS) and molecular dynamics(MD). In situ AFM investigations of protein assembly into extended structures reveal the importance of conformational transformations in controlling pathways and kinetics of matrix assembly. The large barriers associated with these transformation renders them rate-limiting in forming the ordered structures. Consequently, before order can emerge, these systems must be driven to condense into metastable, liquid-like clusters in which protein-protein contact times are large. The emergence of order within these clusters catalyzes the further transformation and attachment of proteins. In addition, DFS measurements show that subtle changes in the binding free energy both between the proteins and with the substrates drive the system to adopt radically different architectures. Moreover, the pathway to the final ordered state can pass through transient, less-ordered conformational states. Thus the concept of a folding funnel with kinetic traps used to describe folding of individual proteins is also applicable to matrix self-assembly. In situ AFM and optical studies of mineral nucleation on organic monolayers and protein matrices show that these surfaces promote nucleation through a reduction of interfacial energy. However, nucleation of the amorphous phase in the calcium phosphate-on-collagen system is observed at supersaturations too low to be explained by classical nucleation theory(CNT). The existence of pre-nucleation clusters provides a potential low-barrier pathway that circumvents the large barriers predicted by CNT. MD simulations of CaCO3 solutions reveal the common occurrence of multi-ion clusters whose calculated pdf spectra are nearly identical to that for amorphous CaCO3. However, the ion diffusivities are similar to those of liquids, suggesting these clusters are liquid-like. Taken together, these results provide new insights into the physical mechanisms controlling biological and biomimetic crystallization, from the formation of the initial protein matrix to the maturation of final crystalline structures.

Session ChRoom: CaMonday, (

Start Ti8:50 PM

9:10 PM

9:30 PM

hairs: Kisaathedral Ro(June 04) 20

ime TM

BPW

M

Gdo

M

VS

ilus, David:oom 0:50 - 21:50

Title BiologicallyPhotocatalytWater Treatm

Growth and doped BaBrCoxygen defe

Vapor GrowStoichiometr

: University

y Inspired Sytically Activment

study of undCl scintillato

ects on perfo

wth and Chemric LiCoO2

y of Californ

ynthesis of a ve Membrane

doped and euor crystals: Irmance

mical DelithiSingle Cryst

nia, Riversi

e for

uropium Impact of

iation of tals

ide

Authors Kinsinger, etal.

Samulon, etal.

Lin, etal.

Durattion20

20

20

Abstract Details:

Session: Date: Time: Room: Energy Materials Growth and Applications 06/04 20:50 Main hall Title: Biologically Inspired Synthesis of a Photocatalytically Active Membrane for Water Treatment Authors: Kinsinger, Nichola 2; Dudchenko, Alexander 2; Wong, Ashley 2; Li, Dongsheng 1; Kisailus, David 2 1Lawrence Berkeley National Laboratory , 2University of California, Riverside Abstract: There is an alarming increase of a variety of new chemicals that are now being discharged into the wastewater system causing increased concern for public health and safety because many are not removed by typical wastewater treatment practices. Titanium Dioxide (TiO2) is a heterogeneous photocatalytic material that rapidly and completely mineralizing organics without harmful byproducts. TiO2 is synthesized by various methods such as chemical and physical vapor deposition, which require high temperatures or extreme atmospheric conditions (e.g., high vacuum) to achieve the desired phase, shape, and size of the material. Solution routes such as chemical bath deposition, sol-gel and hydrothermal routes afford environmentally friendly processing with low cost. However, these solution-based technologies lack the necessary control of crystal size, phase, and morphological features that yield optimized semiconductor materials. Mineralizing biological organisms demonstrate how nature can produce elegant structures at room temperature through controlled organic-mineral interactions. These organics exist as either soluble forms or as insoluble scaffolds that are often used to control size, shape, and phase of deposited mineral. We utilize biologically-inspired scaffolds to template the nucleation and growth of inorganic materials such as TiO2, which aid in controlling the size and phase of these particles and ultimately, their properties. Understanding the fundamental nucleation and growth mechanism is critical to control the microstructure and thus function. Nanosized rutile and anatase particles were synthesized at relatively low temperatures and mild pH conditions. The effects of reaction conditions on phase and grain size were investigated and discussed from coordination chemistry and coarsening mechanisms. Introducing a synthetic and hydrophilic polymer during the reaction yielded a mechanically robust (elastic) composite material consisting of titanium dioxide (TiO2) nanoparticles cross-linked with the polymer. This composite can be subsequently heat-treated in air to pyrolyze the polymer producing a porous, high surface area TiO2 nanoparticle membrane. The size and phase of the resultant TiO2 as well as the porosity of these structures can be modified based on solution parameters. As a photocatalytic material, controlling the phase of TiO2 is anticipated to have a dramatic effect on the recombination rate of electron-hole pairs, thereby increasing the photocatalytic efficiency. These bulk porous TiO2 structures can be fabricated and tailored to act as stand alone photocatalytic membranes, eliminating the need for nanoparticle recovery systems, thereby reducing processing costs and increasing amount of viable applications of photocatalytic systems.

Abstract Details: Session: Date: Time: Room: Energy Materials Growth and Applications 06/04 21:10 Main hall Title: Growth and study of undoped and europium doped BaBrCl scintillator crystals: Impact of oxygen defects on performance Authors: Samulon, Eric 1; Bourret, Edith 1; Yan, Zewu 1; Bizarri, Gregory 1 1Lawrence Berkeley National Laboratory Abstract: BaBrCl was recently found to have good scintillation properties, including high light yield and excellent energy resolution. However, it is well known that defects play an important role in the spectroscopic behavior of the Ba based halide systems. In scaling up the size of crystals, understanding and controlling the presence of defects is vital to maintain performance. We have grown single crystal boules of undoped and Eu doped BaBrCl via the Bridgman technique in a controlled atmosphere. The impact of oxygen defects on the scintillation properties of BaBrCl has been studied from thermoluminescence, x-ray luminescence, absorption and optical emission measurements as a function of the growth conditions. These results highlight the major role played by defect concentration in mixed halides crystals and stress the importance of controlled growth conditions to reach and maintain the high scintillation performance of Ba based halide compounds.

Abstract Details: Session: Date: Time: Room: Energy Materials Growth and Applications 06/04 21:30 Main hall Title: Vapor Growth and Chemical Delithiation of Stoichiometric LiCoO2 Single Crystals Authors: Lin, Qiyin 1; Li, Qingan 1; Gary, K. E. 1; Mitchell, J. F 1 1Materials Science Division, Argonne National Lab Abstract: Layered LiCoO2 compound is widely used as the cathode material of commercial rechargeable Li+ ion batteries due to its high energy and power density and good cycling performance. Single crystals of LiCoO2 are attractive as a model material for studying fundamental electrode properties, such as crystal and electronic structural evolution, Li+ ion and charge carrier transport within electrodes and at the electrode-electrolyte interfaces during battery operation. Here, we report growth of LiCoO2 single crystals using a high temperature vapor transport method. Obtained single crystals are black with a plate-like morphology. Powder and single crystal x-ray diffraction studies confirmed the rhombohedral structure (R-3m space group) of stoichiometric LiCoO2 with lattice parameters a=2.8150(3) Å and c=14.0516(6) Å at room temperature. Electrical transport measurements indicated that as-grown LiCoO2 crystals are highly insulating with ρ300K=0.52-3.4 TΩ·cm, dramatically higher than the value of 5 Ω·cm previously reported for a flux-grown crystal. This high resistivity state is consistent with the previously reported bandgaps, suggesting that crystals have intrinsically fewer defects than those previously reported. As-grown LiCoO2 crystals were delithiated by a chemical extraction process. A quasi-in situ XRD approach was exploited to monitor the structural evolution during the Li-ion extraction process, which exhibited the progression of phases widely established for this system, but also shows evidence of inhomogeneous delithiation mechanism in these macroscopic crystals. Transport measurements confirm an insulator-metal transition behavior in the LixCoO2 system (1.0>x>0.5).

Session ChRoom: CaTuesday, (

Start Ti9:00 AM

9:40 AM

10:20 A

hairs: Kisaathedral Ro(June 05) 09

ime TM

Io

M

MSMB

AM

Iab

ilus, David:oom 9:00 - 10:40

Title Interfacial morganic sem

Materials ChStorage: PhaMechanismsBatteries

In-situ TEMa single nanobattery

: University

morphology aiconductor d

hallenges in ase Transforms, and Degra

M observationowire electro

y of Californ

and thin filmdevices

Electrical Emations, Re

adation in Li-

ns of the opeode in a lithi

nia, Riversi

m order in

Energy action -ion

eration of ium ion

ide

Authors Katz, etal.

Sullivan, etal.

Liu, etal.

Durattion40

40

20

Abstract Details: Session: Date: Time: Room: Energy Materials Growth and Applications 06/05 9:00 Main hall Title: Interfacial morphology and thin film order in organic semiconductor devices Authors: Katz, Howard 1 1Johns Hopkins University Abstract: This talk will focus on four self-assembled systems that provide additional or enhanced function to field-effect transistors. First, a blended p-channel semiconductor will be described that incorporates a polar and nonpolar oligomer side chain in a single phase two-dimensional cocrystal. This ultrathin film optimizes hole mobility and analyte transduction capability. Second, an n-channel small molecule with a side chain well enough packed to contribute to dielectric function will be discussed. Unusual features of this system include a frequency-dependent capacitance and mobility, contributing to transistor operability below one volt and threshold voltage tunability using self-assembled monolayers. Similar principles of self-assembly allow a third system, very simple benzenetetracarboxylic diimides, the monomer unit for polyimides, to show semiconductor activity, though the preferred side chain lengths scale very differently. Finally, use of alkali metal-intercalated aluminas as gate dielectrics for both organic and oxide semiconductor transistors will be presented. While a transition to a crystalline thin film phase was discovered at a higher temperature than the bulk transition temperature, surprisingly high performance was found even in an amorphous phase of the aluminas. The contributions of the ions to dielectric capacitance is clearly shown.

Abstract Details: Session: Date: Time: Room: Energy Materials Growth and Applications 06/05 9:40 Main hall Title: Materials Challenges in Electrical Energy Storage: Phase Transformations, Reaction Mechanisms, and Degradation in Li-ion Batteries Authors: Sullivan, John 1; Huang, J. Y. 2; Shaw, M. J. 1; Zavadil, K. R. 1; Leung, K. 1; Liu, Y. 1; Hudak, N. 1; Hearne, S. J. 1; Subramanian, A. 3; Liu, X. H. 4 1Sandia National Laboratories , 2Self-employed , 3Virginia Commonwealth Univ. , 4Dow Corning Abstract: Advances in electrical energy storage are required in order to enable widespread utilization of plug-in electric vehicles, and, at present, Li-ion batteries offer the highest gravimetric storage capacity of commercially-available technologies. At the most basic level, a Li-ion battery may be considered to be a compact chemical reactor that cycles repeatedly between two end states: a state in which mobile Li+ is bound in a low voltage anode phase (the charged state) and a state in which mobile Li+ is bound in a high voltage cathode phase (the discharged state). Remarkably, modern Li-ion batteries cycle between these states several thousand times with a reaction efficiency exceeding 99.5% per cycle. Inevitably, these reactions are imperfect, and loss in storage capacity or degradation occurs. To study these degradation mechanisms, we have developed new experimental approaches that enable imaging of battery cycling inside a transmission electron microscope (TEM) with atomic-scale spatial resolution and real-time temporal resolution. These studies have revealed a wide variety of reaction mechanisms that can contribute to degradation in high capacity anodes, including the identification of the strain accommodation mechanisms in SnO2, visualization of dislocation-induced amorphization, observation of diffusion anisotropy in silicon anodes and a size dependence to lithiation-induced silicon particle fracture, observation of vacancy coalescence and void formation in germanium, and the discovery that thin aluminum oxide layers react with Li to form an effective solid electrolyte and passivation layer. In addition to these structural studies, we have developed experimental capabilities to examine parasitic reactions within Li-ion batteries related to electrolyte decomposition. These reactions produce a solid product phase, known as the solid-electrolyte interphase (SEI), and its study requires new electrochemical cells that enable imaging inside a TEM while using volatile battery electrolytes. Finally, we note that these specialized liquid cells may also be useful for the in-situ TEM study of general materials synthesis in aqueous or non-aqueous media. This work was supported by an LDRD and the NEES EFRC project and was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of Basic Energy Sciences user facility. Sandia is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. DOE’s NNSA under contract DE-AC04-94AL85000.

Abstract Details: Session: Date: Time: Room: Energy Materials Growth and Applications 06/05 10:20 Main hall Title: In-situ TEM observations of the operation of a single nanowire electrode in a lithium ion battery Authors: Liu, Yang 1; Liu, Xiao Hua 1; Zhu, Ting 2; Li, Ju 3; Zhang, Suling 4; Huang, Jian Yu 1 1Sandia National Laboratories , 2Georgia Institute of Technology , 3Massachusetts Institute of Technology , 4Pennsylvania State University Abstract: Lithium ion batteries (LIBs) are broadly used in portable electronics, where the high energy/power density, good cyclability as well as low cost are important. A fundamental understanding of the microstructural change of the electrodes and solid-electrolyte interface (SEI) layer during battery operation, especially at the atomic scale, is highly desired. We created the first nanobattery inside a transmission electron microscope (TEM), allowing for real time and atomic scale observations of battery charging and discharging processes. In this presentation, I will show two examples, one is the anisotropic expansion of Si nanowire upon lithiation and the other is the pulverization of Al nanowire and the evolution of the thin surface Al2O3 layer upon cycling. Silicon is being considered as one of the leading candidates of the anode materials in LIBs for its high theoretical capacity. However, due to the huge volume changes (~300%) induced by Li insertion and extraction, the poor cyclability remains the major obstacle to prevent it from commercialization. The deformation and failure mechanisms are still not well understood. In the in-situ TEM experiment, we found the anisotropic expansion of Si nanowire upon lithiation. The lithiated <112> direction Si nanowire had a dumbbell-shaped cross section, showing the largest swelling along the radial <110> directions and the smallest swelling along the radial <111> directions. The insertion/extraction of a large amount of lithium in the active materials can induce large mechanical stresses that can further cause pulverization leading to the loss of electrical contact and capacity fading after a few cycles. We have used the in-situ TEM electrochemistry to study the pulverization processes by taking the Al nanowire as a model system. Voids were formed in the Al NWs at the first delithiation process and grew continuously at each following delithiation cycles, leading to pulverization of the Al NWs to isolated nanoparticles. The surface Al2O3 layer evolved into a stable Li-Al-O glass tube, which survived the 100% volume expansion and confined the pulverized Al nanoparticles, showing the exceptional mechanical robustness. The results provide important insight into the degradation mechanism of metal electrodes and into the recent reports about the performance improvement of LIBs by atomic layer deposition of Al2O3 coating on the active materials. Acknowledgement: Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Session ChRoom: CaTuesday, (

Start Ti11:10 A

11:50 A

hairs: Kisaathedral Ro(June 05) 11

ime TAM

CEM

AM

I(m

ilus, David:oom 1:10 - 12:10

Title Colloidal CrElectrophoreModeling

Influence of (Ribbon gromorphology

: University

rystal Assemetic Depositi

f nucleation cwth on subs

y

y of Californ

mbly by ion – Experi

conditions otrate) crysta

nia, Riversi

iments and

on RGS al

ide

Authors Kuntz, etal

Pichon, etal.

Durat.

tion40

20

Abstract Details: Session: Date: Time: Room: Energy Materials Growth and Applications 06/05 11:10 Main hall Title: Colloidal Crystal Assembly by Electrophoretic Deposition – Experiments and Modeling Authors: Kuntz, Joshua 1 1Lawrence Livermore National Laboratory Abstract: Precise control over a material's microstructure is required to manufacture materials with novel properties. Electrophoretic deposition (EPD), in which suspended colloids are driven to an electrode by an electric field, is an attractive manufacturing technique because it inherently operates at the nanoscale. To this end, the electrophoretic deposition (EPD) provides an elective and low-cost method for producing designer materials with a specific microstructure. Although the basic mechanisms of electrophoretic deposition are well-known and have been studied extensively, a detailed, quantitative model for the dynamics and kinetics of deposition is still lacking. Understanding the full deposition process and the influence of various parameters on the microstructure of deposits will play a crucial role in the optimization of the deposition process in experiments. While the leading effect at play in electrophoretic deposition is linear electrophoresis, dynamics in suspension and deposition on the electrode are also affected by a number of other phenomena and interactions, including dielectrophoretic (dipolar) interactions (DEP), induced-charge electrophoresis (ICEP, only for polarizable particles), Brownian motion, stearic interactions, and van der Waals interactions, as well as hydrodynamic interactions between particles and with the electrodes. Here, we present techniques for fabricating complex 2D and 3D structures via field sculpted EPD over dynamic electrodes as well as detail the results of computational modeling efforts that enable the prediction of the deposition dynamics and final structure. Specifically, a correlation between experimental and modeling conditions required for ordered “crystalline” deposition versus disordered “amorphous” deposition. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Abstract Details: Session: Date: Time: Room: Energy Materials Growth and Applications 06/05 11:50 Main hall Title: Influence of nucleation conditions on RGS (Ribbon growth on substrate) crystal morphology Authors: Pichon, Pierre-Yves 1; Schönecker, Axel 1 1RGS Development BV Abstract: Silicon wafer for solar cell applications can be produced in one step by the RGS technique. This process allows production speed in the order of 1 wafer per second and complete suppression of cutting losses. Textured substrates at initial temperature below the melting point of silicon are moved at a constant speed under the molten silicon bath. The substrate temperature below the equilibrium melting point provides the driving force for nucleation and crystal growth. Since the heat extraction is perpendicular to the wafer transport, the production rate is decoupled from the crystallization velocity. Understanding the formation of the thermal and mechanical contact between the wafer and the substrate is of high importance to improve the material quality. Only a small portion of the wafer surface is contacting the substrate through discrete contact points, which are the summits of the substrate surface texture. Since most of the crystallization heat is transferred through these contact points, the growth conditions are strongly affected by their size and distribution. In addition, after casting, stress is built due to difference in thermal expansion between the wafer and the substrate which loosen these contact points. At the same time plastic deformation of the wafer can possibly initiate and/or multiply dislocations.It was found that a better thermal/mechanical contact leads to higher growth velocity, smaller grain size and higher dislocation density. In addition, minority carrier lifetime measurements showed that a better contact can have a negative effect on the lifetime and therefore the electrical properties of the material. The important parameters influencing the formation of the thermal and mechanical contact were studied during casting experiments. It was found that the initial temperature of the substrate and the initial silicon melt temperature are strongly influencing the formation of the thermal contact. We analyzed the results in view of the classical theory of nucleation (Turnbull 1950). The substrate texture and material, in combination with the pressure of the silicon bath are also influencing the thermal contact. This indicates that wetting plays an important role. Under certain conditions it was found that the crystallization front can form twinned dendritic crystals. This was attributed to a driving force for crystal growth being higher than the driving force for nucleation.

Session ChRoom: CaTuesday, (

Start Ti7:30 PM

8:10 PM

8:30 PM

hairs: Kisaathedral Ro(June 05) 19

ime TM

PM

M

Apm

M

GPH

ilus, David:oom 9:30 - 20:50

Title Progress in NMaterials an

All-epitaxialpatterned gamid-IR laser

Growth of NPalladium AHigh Power

: University

Nonpolar annd Devices

l growth of oallium phospr application

Nanoporous PAlloys in Sof

Density Hy

y of Californ

nd Semipolar

orientation-hide (OPGa

ns

Palladium anft Templates drogen Stora

nia, Riversi

Ar GaN S

aP) for Se

nd for age

Ce

ide

Authors Speck, etal.

Schunemanntal.

Cappillino, tal.

Durat

,

tion40

20

20

Abstract Details:

Session: Date: Time: Room:

Energy Materials Growth and Applications 06/05 19:30 Main hall

Title: Progress in Nonpolar and Semipolar GaN Materials and Devices

Authors: Speck, James 1 1UC Santa Barbara

Abstract: Devices grown on c-plane GaN suffer from large internal electric fields due to discontinuities in spontaneous and piezoelectric polarization effects which cause charge separation between holes and electrons in quantum wells and limits the radiative recombination efficiency. Nonpolar GaN devices, such as in the m-plane (1100), are free from polarization related electric fields since the polar c-axis is parallel to any heterointerfaces. Semipolar GaN-based devices have reduced electric fields and in some cases, such as (2021), show a high propensity for Indium update for InGaN quantum wells.

In this talk, we present work on outstanding materials and device opportunities issues and opportunities including: morphological stability with special emphasis on the role of substrate orientation and growth conditions [1,2,3]; the development of pseudomorphoric InGaN and AlGaN semipolar buffer layers via dislocation strain relaxation [4,5,6,]; blue (1122) LDs in relaxed buffer layers [7]; green LEDs on relaxed buffer layers [8]; new detailed atom probe analysis of high performance GaN-based LEDs and laser diodes [9]. Additionally, we update progress on nonpolar electron devices and nonpolar and semipolar LEDs and LDs including the achievement of high performance true blue (λ >450 nm) and true green (λ >515 nm) lasers on m-plane and semipolar (namely, (2021)) GaN substrates [10,11]. Finally, we will present recent work on polarized light emission from m-plane LEDs [12] and demonstrate the first photonic crystal nonpolar LEDs [13].

[1]R.M. Farrell et al J. Cryst. Growth313,1(2010) [8]I. Koslow et al. submitted for publication(2012)

[2]R.M. Farrell et al Appl. Phys. Lett.96,231113(2010) [9]T. Prosa et al. Appl. Phys. Lett.98,191903(2011)

[3]B. Bryant et al submitted for publication(2012) [10]K.M. Kelchner et al Appl. Phys. Express3,092103(2010)

[4]F. Wu et al J. Appl. Phys.109,033505(2011) [11]Y.D. Lin et al. Appl. Phys. Express3,082001(2010)

[5]A.E. Romanov et al, J. Appl. Phys.109,103522(2011) [12]S.E. Brinkley et al. Appl. Phys. Lett.98,011110(2011)

[6]E.C. Young et al. Appl. Phys. Express,4,061001(2011) [13]E. Matioli et al. Appl. Phys. Lett.98,251112(2011)

[7]P.S. Hsu et al. Appl. Phys. Lett.100,021104(2012)

Abstract Details: Session: Date: Time: Room: Energy Materials Growth and Applications 06/05 20:10 Main hall Title: All-epitaxial growth of orientation-patterned gallium phosphide (OPGaP) for mid-IR laser applications Authors: Schunemann, Peter 1; Mohnkern, Lee 1; Vera, Alice 1; Lin, Angie 2; Tassev, Vladimir 3; Snure, Michael 3 1BAE Systems, Inc. , 2Stanford University , 3Air Force Research Laboratory Abstract: Orientation patterned gallium phosphide (OPGaP) is an exciting new engineered nonlinear optical crystal efficiently for shifting widely available 1-micron laser sources deep into the mid-infrared. OPGaP templates were grown by MBE in a dedicated Varian Gen II MOD system modified by the addition of a small auxiliary chamber equipped with a hi-temperature thermal silicon cell for growing the lattice-matched, non-polar Si inversion layer. The system was also equipped with a two-zone phosphorus cracker for improved control of the P flux compared to prior work based on a GaP solid source. After loading and baking (300°C) a 3-inch GaP vicinal (100) substrate (4° off cut toward <111B>) in the system, a 200-nm-thick buffer was grown at a rate of 200 nm /h under a P pressure of 1.1x10-6 torr (~ 10 times higher than reference 5) at a substrate temperature of 500°C, followed by growth of 5 nm of Si at a rate of 15 nm/h while ramping the substrate temperature from 380°C to 450°C. A 2.7-nm-thick AlGaP smoothing layer and then a 100-nm-thick inverted GaP layer were grown at 200 nm/hr at P pressures of 3.3 x 10-7 torr and 4.3 x 10-7 torr respectively. The GaP inverted layer was then photolithographically patterned with grating periods ranging from 14.5 to 95.9 microns, then etched by reactive ion etching in BCl3 at rates of ~ 2 nm/s (0.4 nm/s for Si) down to the surface of the original substrate. After removing the photoresist the wafer was cleaned with a brief wet etch and reloaded into the MBE chamber for 200 nm of regrowth under the same conditions as the initial GaP buffer layer. Atomic Force Microscopy revealed that the inverted layer growth was free of anti-phase domains, and that the patterned grating structure exhibited good vertical propagation. The resulting 3-inch MBE-grown OPGaP templates were cleaved into quarters and preliminary low-pressure hydride vapor phase epitaxy (LP-HVPE) growth experiments were performed at the Air Force Research Laboratory (AFRL) in a horizontal hot-wall quartz reactor. Growth was performed at temperatures between 700°C and 740°C, pressures below 10 torr, and relatively low III/V ratios and low supersaturation. Total gas flow through the system, including phosphine (PH3), HCl (flowing over Ga to form GaCl), and hydrogen carrier gas (H2) was less than 250 sccm. Layer thicknesses in excess of 70 microns were achieved, and initial inspection of the domain propagation is adequate for initial device testing.

Abstract Details: Session: Date: Time: Room: Energy Materials Growth and Applications 06/05 20:30 Main hall Title: Growth of Nanoporous Palladium and Palladium Alloys in Soft Templates for High Power Density Hydrogen Storage Authors: Cappillino, Patrick 1; Parent, Lucas 2; Hekmaty, Michelle 1; Jacobs, Benjamin 3; Hartnett, Ryan 1; Arslan, Ilke 2; Robinson, David 1 1Sandia National Laboratories/CA, Energy Nanomaterials , 2University of California - Davis, Dept. of Chemical Engineering , 3Protochips, Inc. Abstract: Nanoporous palladium and palladium alloys are high-performance hydrogen storage materials and metal hydride electrodes, with volumetric power densities about 1000x higher than commercial lithium ion batteries. Common approaches to synthesis of such materials using various metals involve chemical or electrochemical reduction in a molecular template that constrains particle growth on the nanometer scale. Palladium presents a special challenge due to the autocatalytic nature of its growth, which can disrupt the templating, resulting in disordered pores. We have used fluid-stage TEM for in situ observation of growth of the particles within soft templates. Small seed particles form that eventually sinter around the template. With the most commonly used surfactant templates, we observe overgrown particles that break through and migrate within the template structure. However, block copolymer templates form stronger micellar structures that more effectively constrain growth and lead to ordered, tunable porosity. When alloys are used (such as with Rh or Pt), growth of seed particles is also constrained, resulting in ordered porosity with the small-molecule surfactants. The crystallite size in the products is at or below the scale of the pore size, and this influences the thermal stability of the material, an important criterion for practical use. Heated-stage TEM and electron tomography reveal both surface and grain boundary effects in thermal degradation. Control of these allows significant improvements in thermal properties with minimal sacrifice of hydrogen storage capacity and power density. References: L. R. Parent, D. B. Robinson, T. J. Woehl, W. D. Ristenpart, J. E. Evans, N. D. Browning, and I. Arslan. "Direct in Situ Observation of Nanoparticle Synthesis in a Liquid Crystal Surfactant Template." ACS Nano, http://dx.doi.org/10.1021/nn300671g. M. D. Ong, B. W. Jacobs, J. D. Sugar, M. E. Grass, Z. Liu, G. M. Buffleben, W. M. Clift, M. E. Langham, P. J. Cappillino,and D. B. Robinson. “Effect of Rhodium Distribution on Thermal Stability of Nanoporous Palladium−Rhodium Powders.” Chem. Mater. 24 (6) 996-1004 http://dx.doi.org/10.1021/cm202688m M. P. Klein, B. W. Jacobs, M. D. Ong, S. J. Fares, D. B. Robinson, V. Stavila, G. J. Wagner, and I. Arslan. "3-D Pore Evolution of Nanoporous Metal Particles for Energy Storage." J. Am.

Session ChRoom: CaTuesday, (

Start Ti8:50 PM

9:30 PM

hairs: Zepeathedral Roo(June 05) 20

ime TM

Ig

M

Dg

eda-Ruiz, Luom 0:50 - 21:50

Title Interfacial engrowth of go

Direction-spgrowth by or

uis: Lawre

nergetics anold-catalyzed

pecific interariented attac

nce Liverm

d morphologd silicon nan

actions contrchment

more Nationa

gy during nowires

rol crystal

al Laborato

Authors Upmanyu, etal.

Li, etal.

ory

Durattion40

20

Abstract Details: Session: Date: Time: Room: Fundamentals of Materials Growth 06/05 20:50 Main hall Title: Interfacial energetics and morphology during growth of gold-catalyzed silicon nanowires Authors: Upmanyu, Moneesh 1; Wang, Hailong 2; Zepeda-Ruiz, Luis 3; Gilmer, George 4 1Northeastern University , 2Brown University , 3Lawrence Livermore National Laboratory , 4Colorado School of Mines Abstract: Applications aimed at harnessing the multifunctional properties of semiconducting nanowires require precise yet scalable control over nanowire morphology and composition. The vapor-liquid-solid (VLS) synthesis technique continues to be a promising route yet efforts to tailor the growth remain handicapped primarily due to a lack of understanding of of the underlying atomic-scale processes. Current understanding remains limited to continuum frameworks with attendant assumptions regarding the nucleation dynamics as well as the morphology, energetics and kinetics of the associated interfaces. In this talk, I will present fully 3D atomic-scale computations on a small diameter, gold-catalyzed <111> silicon nanowire that uncover a complex faceted morphology of the nanowire-particle interphase, and segregation at the droplet surface and the interphase. Studies with supersaturated droplets identify an interplay between segregation and the diffusive kinetics necessary for interphase silicon nucleation and subsequent nanowire growth. The silicon-rich solid-like surface layer suppresses surface diffusion to an extent that the excess Si-flux is carried by the bulk of the particle, while the Si segregation at the faceted interphase depresses the barrier for nucleation at the truncating facets. The subsequent step flow is controlled by gold diffusion away from the step edges into the droplet and the nanowire sidewalls. At large supersaturations, we see evidence for gold trapping within the crystallized Si, indicating the possibility of doping nanowires via highly non-equilibrium routes. Our results identify interfacial characteristics and their design as a key ingredient for scalable synthesis of silicon and related multicomponent semiconducting nanowires.

Abstract Details: Session: Date: Time: Room: Fundamentals of Materials Growth 06/05 21:30 Main hall Title: Direction-specific interactions control crystal growth by oriented attachment Authors: Li, Dongsheng 1; Nielsen, Michael 2; Lee, Jonathan 3; Frandsen, Cathrine 4; Banfield, Jillian 5; De Yoreo, James 6 1Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA , 2Department of Materials Science and Engineering, University of California, Berkeley, CA , 3Physical Sciences Directorate, Lawrence Livermore National Laboratory, Livermore , 4Department of Physics, Technical University of Denmark, 2800 Kongens Lyngby, Denmark , 5Earth Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA , 6The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA Abstract: Oriented attachment (OA) of molecular clusters and nanoparticles in solution is now recognized as an important mechanism of crystal growth in many materials, yet the alignment process and attachment mechanism have not been established. Here we performed high-resolution TEM using a fluid cell to directly observe oriented attachment of iron oxyhydroxide nanoparticles. The particles undergo continuous rotation and interaction until they find a perfect lattice match. A sudden “jump to contact” then occurs over < 1nm, followed by lateral atom-by-atom addition initiated at the contact point. Interface elimination proceeds at a rate consistent with the curvature-dependence of the Gibbs free energy. Measured translational and rotational accelerations show that strong, highly-direction-specific interactions drive crystal growth via OA. The findings of this study provide a dynamic view of the process of OA and answer the essential question of whether co-alignment occurs prior to attachment or comes about afterwards. The results imply that, in the case of freely diffusing nanoparticles, the conditions for attachment are very specific: either near-perfect crystallographic orientation or a specific twin orientation that ensures interfacial coherence is required. In the event that a particle becomes trapped between two adjacent particles, the applied pressure can drive attachment in a misaligned state, though this condition is transient and atomic rearrangements quickly lead to co-alignment. The results also shed light on the magnitude and nature of the forces that drive OA. More generally, although amicrofabricated in situ TEM fluid cells have been previously used to observe growth of metallic nanoparticles and films at relatively low resolution, this study demonstrates they can also enable observations of dynamic phenomena with lattice-fringe resolution in a wide range of nanomaterials of importance in both synthetic and natural environments.

Session ChRoom: CaWednesda

Start Ti9:00 AM

9:40 AM

10:00 A

10:20 A

hairs: Zepeathedral Rooay, (June 06

ime TM

GN

M

ESS

AM

Oc

AM

Uff

eda-Ruiz, Luom ) 09:00 - 10

Title Growth and Nanoparticle

Electroless AScalable AppStructures

Onset of crycolloidal nan

Understandifor Improvinfor Radiation

uis: Lawre

:40

Design of Ne Catalysts

Atomic Layeproach to Ta

ystallization inoparticles

ng the Fundng the Grown Detectors

nce Liverm

Nanoporous

er Depositionailored Surfa

in assemblie

damental Chath of CZT C

more Nationa

n: a ace

es of

allenges Crystals

al Laborato

Authors Erlebacher,etal.

Robinson, etal.

Sehgal, etal

Derby, etal

ory

Dur,

l.

.

ration40

20

20

20

Abstract Details: Session: Date: Time: Room: Fundamentals of Materials Growth 06/06 9:00 Main hall Title: Growth and Design of Nanoporous Nanoparticle Catalysts Authors: Erlebacher, Jonah 1; Snyder, J. 1 1Johns Hopkins Abstract: Nanoporous metals with pore and ligament diameters less than 10 nm are useful in a variety of applications, from sensors to fuel cells. Such materials combine the attractive features of high surface area/volume nanoparticles with the high electrical conductivity of bulk materials. In fact, the concept of a “nanoporous nanoparticle,” is especially attractive, as such materials should be very robust under catalytically active conditions, one can turn them into highly active composites by filling the pores with secondary phases that enhance reactivity, and they should be easily integrated into nanoparticle-based technologies. In this presentation, I will discuss the chemistry and physics of nanoporous nanoparticle growth and subsequent electrochemical dealloying, with an emphasis on the Ni-Pt system, which is relevant for fuel cell oxygen reduction. Three fundamental issues associated crystal growth will be discussed. First, in order to induce nanoporosity, techniques to grow monodisperse single-crystal alloy nanoparticles with diameter range in the 10-20 nm region needed to be developed, as well as techniques to homogenize the composition of the alloy particles. Second, the electrochemistry of porosity evolution during dealloying of nanometer-scale objects needed to be elucidated, and we found here that an apparent “inverse Gibbs-Thomson (GT)” effect is operative – essentially, there is a competition between the GT effect applied to the undissolved component (Pt) and the GT effect applied to dissolution (of Ni). Third, we have elucidated the experimental conditions under which Pt-skin nanoporous nanoparticles are formed during dealloying, and show that this leads to extremely active catalysts for oxygen reduction, with mass activities at 0.9 V vs. RHE over 1.2 mA/cm^2.

Abstract Details: Session: Date: Time: Room: Fundamentals of Materials Growth 06/06 9:40 Main hall Title: Electroless Atomic Layer Deposition: a Scalable Approach to Tailored Surface Structures Authors: Robinson, David B. 1; Cappillino, Patrick J. 1; Sheridan, Leah B. 2; Stickney, John L. 2 1Sandia National Laboratories , 2University of Georgia Abstract: Electrochemical Atomic Layer Deposition is a two-step process that exploits the fact that some materials electrodeposit as a monolayer onto a dissimilar substrate at a less negative potential as they would deposit onto themselves. In the second step, yet another dissimilar material is deposited, or a more noble element displaces the first. The process can be repeated with varying reagents, allowing deposition of nanoscale structures, including superlattices of compound semiconductors, and multilayer noble metal films for catalysis and sensing. The films can be grown to arbitrary thicknesses, albeit one layer at a time. This is typically done in an electrochemical flow cell, so milliliter quantities of deposition and rinse electrolytes are needed for each step. When scaled up for substrates with high surface areas, large electrical current sources may be required. We have developed versions of this method in which a surface hydride is formed by electrochemical or electroless (chemical) deposition, and the hydride is then displaced by a more noble element in a surface-limited reaction. If the more noble element also forms a surface hydride, this process can be repeated. If the hydride can be formed chemically, such as by exposure to H2 gas or a hydride-containing reducing agent, the electrochemical instrumentation need not scale with the substrate size, and electrical contact to the substrate is not required. The displacing element can be potentiometrically titrated, allowing growth in a batch reactor, so the waste stream does not scale with sample size, as it would with a flow cell. While we are primarily studying catalytic noble metal films and sensors, we believe that this can be a widely applicable approach to the large-scale preparation of crystalline materials that have precisely defined nanoscale structure, and to the enhanced mechanical, electrical, thermal, optical, or other properties that are predicted to result from this.

Abstract Details: Session: Date: Time: Room: Fundamentals of Materials Growth 06/06 10:00 Main hall Title: Onset of crystallization in assemblies of colloidal nanoparticles Authors: Sehgal, Ray 1; Beltran-Villegas, Daniel 2; Bevan, Michael 2; Ford, David 1; Maroudas, Dimitrios 1 1University of Massachusetts Amherst , 2Johns Hopkins University Abstract: We report results of a systematic investigation of the phase behavior of clusters of colloidal nanoparticles. The goal of this investigation is to observe the onset of crystallization as a function of both system size and interparticle interaction strength. These colloids interact via a electrostatic repulsion and depletion attraction potential. To describe the various phases that may be present in such nanoparticle assemblies, we carry out a set of windowed Monte Carlo umbrella sampling (MC-US) simulations to generate free energy landscapes (FELs). The resulting set of FELs samples broad ranges of the system size and interaction potential strength. These computed FELs describe the phase behavior of the nanoparticle assemblies and allow us to analyze the effects of interaction strength and system size as these assemblies approach the bulk thermodynamic limit. In very small clusters, only a single stable liquid-like phase exists. However, as the number of nanoparticles in the cluster increases, a second crystalline phase emerges in coexistence with the liquid-like phase. The corresponding critical cluster size marks the onset of nucleation and crystalline growth of assemblies of colloidal nanoparticles.

Abstract Details:

Session: Date: Time: Room:

Fundamentals of Materials Growth 06/06 10:20 Main hall

Title: Understanding the Fundamental Challenges for Improving the Growth of CZT Crystals for Radiation Detectors

Authors: Zhang, Nan 1; Yeckel, Andrew 1; Derby, Jeffrey 1 1University of Minnesota

Abstract: The availability of large, single crystals of cadmium zinc telluride (CZT) with uniform properties is key to improving the performance of gamma radiation detectors fabricated from them. However, the growth of these crystals is not well understood, and most modifications to crystal growth have been driven by intuition obtained from experience with traditional semiconductor systems that behave very differently from CZT. We aim to advance the practice of CZT growth by applying physics-based, computational models to understand the fundamental factors affecting the process.

Bulk CZT growth is plagued by numerous challenges, ranging from macrosegregation of composition to microscale structural flaws. In this presentation, we focus on recent results that provide a deeper understanding of crystal growth processes and suggest how the growth of CZT can be improved. In particular, we emphasize two issues. First, we show how the inherent properties of CZT can result in the Bridgman growth of crystals exhibiting non-classical zinc distributions. This surprising result is consistent with many prior growth outcomes where “anomalous” zinc distributions have been observed, quite different from the segregation behavior exhibited by traditional Bridgman growth systems. Next, a novel, bell-curve furnace temperature profile is presented and predicted to achieve macroscopically convex solid-liquid interface shapes during melt growth of CZT in an electrodynamic gradient freeze (EDG) furnace. A strategy is also presented to dynamically adapt this furnace profile so that uniform, convex interface shapes are maintained through an entire CZT growth run. This approach represents a significant advance over traditional gradient-freeze profiles, which always result in concave interface shapes, and furnace heat transfer modifications, such as redesigned ampule support pedestals, that can achieve convex interfaces, but only over only a small portion of the growth run.

Realizing a convex solidification interface via this adaptive bell-curve furnace profile is postulated to result in better crystallinity and higher yields than conventional CZT growth techniques. We make the case that these results can be put directly into practice using existing, multiple-zone growth systems. Indeed, evidence will be presented from experimental practice that these ideas are quite promising.

____________ Supported in part by DOE/NNSA, DE-FG52-08NA28768, the content of which does not necessarily reflect the position or policy of the United States Government, and no official endorsement should be inferred.

Session ChRoom: CaWednesda

Start Ti11:10 A

11:50 A

hairs: Zepeathedral Rooay, (June 06

ime TAM

ND

AM

OMM

eda-Ruiz, Luom ) 11:10 - 12

Title Nucleation CDeposition a

One-dimensMechanism,Materials Ap

uis: Lawre

:10

Control in Aand Hydroge

ional Nanos Assembly Mpplications

nce Liverm

Atomic Layeren Storage R

structures: GManipulation

more Nationa

r Reactions

Growth n, and

al Laborato

Authors Clemons, etal.

Olson, etal

ory

Durat

.

tion 40

20

Abstract Details: Session: Date: Time: Room: Fundamentals of Materials Growth 06/06 11:10 Main hall Title: Nucleation Control in Atomic Layer Deposition and Hydrogen Storage Reactions Authors: Clemons, Bruce 1; Chung, Chia-Jung 1; Bent, Stacey 1; Lee, Han-Bo-Ram 1; Mullings, Marja 1 1Stanford University Abstract: The rate at which nucleation occurs in reactions and film growth dominates the resulting morphology (and hence material properties), as well as, in some cases, controlling the phase formation rate. In most phase formation situations, the density and location of nucleation is not controlled, resulting in difficulty in isolating and studying this important kinetic process. In this talk we present two cases where we have developed the ability to control and study nucleation processes. The reaction of Mg to form the hydride MgH2, has been explored as a possible hydrogen storage system due to the relatively large hydrogen content. Studies aimed at understanding the sluggish kinetics of this nucleation and growth process have shown that the growth rate is limited by diffusion of hydrogen through the growing hydride, but little has been done to control and study the nucleation process. Here we use Pd nanoparticles on Mg thin films to control the nucleation density. These Pd nanoparticles act as nano-portals for introduction of hydrogen to controlled regions of the Mg film. By modeling the resulting transformation behavior we extract the first estimate of a nucleation time constant for a hydrogen storage reaction. The process of atomic layer deposition often exhibits a so-called “incubation” period, during which the mass deposited per deposition cycle gradually increases to a steady-state value. During this incubation period, films are often discontinuous particles rather than a continuous layer. As growth proceeds, the particles grow, new particles are nucleated, and the film becomes continuous as the particles merge together, resulting in the steady-state growth rate. Here we use defected self-assembled monolayers to control the nucleation site density during the incubation period of growth. We model the growth process and show that the resulting behavior is consistent with a time-dependent nucleation process, where nucleation sites are activated and then used up during growth.

Abstract Details: Session: Date: Time: Room: Fundamentals of Materials Growth 06/06 11:50 Main hall Title: One-dimensional Nanostructures: Growth Mechanism, Assembly Manipulation, and Materials Applications Authors: Olson, Tammy 1; Chernov, Alexander 1; Orme, Christine 1; Pascall, Andrew 1; Worsley, Marcus 1; Murphy, Kristen 1; Satcher, Joe 1; Kuntz, Joshua 1; Han, T. Yong-Jin 1 1LLNL Abstract: Zinc oxide (ZnO) and fluorapatite (FAP) have desirable materials properties for various applications and both belong to the hexagonal crystal system to readily form one-dimensional nanorods. Controlled crystal growth and manipulation (i.e. 2 and 3D arrangement) of the nanorods allow tailoring of the materials’ properties for a specific function such as in a device or composite material. ZnO nanowire 2D arrays were fabricated on a silicon substrate and their growth mechanism was explored based on the concept of geometrical selection. The theory states that randomly oriented crystallites can be grown as an oriented film or array of nanowires due to a preferential growth direction; in the case of ZnO, the c-axis. Initial seed crystals with their c-axis perpendicular to the substrate survive, whereas seed crystals with their c-axis deviated from the perpendicular line are eliminated. To examine this growth phenomenon experimentally, ZnO nanowire arrays were grown and their length and crystal density measurements as a function of growth time obtained. A detailed analysis found the results to match closely with the prediction based on the geometrical selection model. Such understanding will allow improved interpretation of the effects of certain parameters, such as substrate type, on the resulting orientation of the nanowire array. Peptides identified as ZnO binding through phage display were utilized as a means to modify the morphology of the nanowires. FAP nanorods were synthesized and an electric field was used to manipulate and assemble them for fabricating transparent ceramics. The optical properties of fluorapatite (FAP) make them promising candidates for laser applications. Recent advancement in laser ceramic manufacturing has shown FAP nanoparticles slip cast and manipulated in a magnetic field to create optically transparent, laser grade ceramics due to alignment of their crystal orientation. Electrophoretic depsition (EPD) offers a much more simple and less expensive alternative. We report the controlled synthesis and characterization of single crystal FAP nanorods for alignment and deposition by EPD. Layers of aligned FAP were then created by an AC and DC field in a EPD cell, which will eventually be sintered to transparency. Controlled synthesis of FAP has a number of other implications and device assembly using the electrophoretic deposition technique will be discussed in greater detail.