august 3rd and 4 , 2016 university of texas at dallas...

AVS Texas Chapter Conference 2016

August 3rd and 4th, 2016

University of Texas at Dallas

Agenda

AVS Texas Chapter Conference 2016 Wednesday, August 3rd SPN – HR Training Room Session I Moderator: M. Goeckner, University of Texas at Dallas 8.10 – 8.20 am

Welcome Remarks

8.20 – 8.40 am A Comprehensive CV Simulation and Extraction Tool for Advanced MOS Device Analysis with Alternative Channels (SiGe and InGaAs) S. R. M. Anwar1, W. G. Vandenberghe1 , R. V. Galatage1, E. M. Vogel2, C. L. Hinkle1 1 Electrical Engineering and Materials Science and Engineering, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080 2 Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Dr., N.W., Atlanta, GA 30332

8.40 – 9.00 am In situ surface and interface study of crystalline (3×1)-O on InAs Xiaoye Qin1, Wei-E Wang2, Mark S. Rodder2, Robert M. Wallace1

1Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, USA 2 Advanced Logic Lab, Samsung Semiconductor, Inc, Austin, Texas 78754, USA

9.00 – 9.20 am Atomic Structure of Cross-linked (1 × 2) Rutile TiO2(110) Yaobiao Xia, Ke Zhu, Zhenrong Zhang, Kenneth T. Park Department of Physics, Baylor University, Waco, Texas 76798, United States of America

9.20 – 9.40 am Selectively removing the carbon overlayer in surface analysis: enhanced information using gas cluster cleaning C.E. Moffitt1, J. Counsell2 1Kratos Analytical, Inc., 100 Red Schoolhouse Rd., Chesntut Ridge, NY 10977, USA 2Kratos Analytical, Ltd., Wharfside, Trafford Wharf Road, Manchester M171GP, UK

9.40 – 10.00 am Super-Resolution Imaging Using Multi-Pulse Pumping of a Long Lived Fluorophore Sebastian Requenaa, Sangram Rauta,b,c, Hung Doana, Joe Kimballa, Rafal Fudalab,c, Julian Borejdob,c, Ignacy Gryczynskib,c, Zygmunt Gryczynskia,b,c, and Yuri M. Strzhemechnya

aDept, of Physics & Astronomy, Texas Christian University, TCU Sid Richardson Building, TCU Box 298840, Fort Worth, TX 76129 b Center for Fluorescence Technologies and Nanomedicine Dept. of Molecular Biology and Immunology University of North Texas, Health Science Center 3500 Camp Bowie Blvd, Ft. Worth, TX 76107 c.Dept. of Molecular Biology & Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., RES-402, Fort Worth, TX 76107

10.00 – 10.20 am Coffee Break SPN, lobby area Session II Moderator: C. Moffitt, Kratos Analytical, Inc. 10.20 – 10.40 am

Studying Copper Sulfide Chemical Bath Deposition Reactions on Organic Surfaces J. K. Orbeck1, R.P. Joshi1, and A.V. Walker1,2 1Department of Chemistry & Biochemistry BE26, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080 2Department of Materials Science & Engineering RL10, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080

10.40 – 11.20 am Invited Talk Silicon Nanotubes: A Diverse Platform for Therapeutics and Energy Jeffery L. Coffer Department of Chemistry, Texas Christian University, Fort Worth, TX 76129

11.20 – 11.40 am Electroless Deposition of Copper on Functionalized SAMs: The Effect of the Reducing Agent on Selective Deposition A.A. Ellsworth1, A. V. Walker1,2

1Department of Chemistry and Biochemistry, University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX, 75080 2Department of Materials Science & Engineering, University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX, 75080

11.40 am - noon The Case for Digital Fabrication at the Atomic Scale (The Inverse Moore’s Law) and Zyvex Labs Approach J.N. Randall, J.B. Ballard, J.H.G. Owen, E. Fuchs, S. Pryadkin, S. Schmucker, J. Lake Zyvex Labs, 1301 N. Plano Rd. Richardson Texas 75081

Noon – 1.00 pm Lunch SPN, Lobby Area Session III: Session Honoring the New PhDs of the AVS Texas Chapter Moderator: S. Zollner, New Mexico State University 1.00 – 1.30 pm Quantum Transport and Dielectric Response of Nanometer Scale

Transistors Jingtian Fang Department of Physics and Astronomy, Vanderbilt University, 2201 West End Ave, Nashville, TN 37235

1.30 – 2.00 pm Structural and Magnetic properties of ion beam synthesized binary and ternary transition metal silicides Wcikramaarachchige J. Lakshantha , Satyabrata Singh, Bibhudutta Rout Ion Beam Modification and Analysis Laboratory, Department of Physics,

University of North Texas, Denton, Texas 76203

2.00 – 2.30 pm Improvements for Thin Film Solid State Neutron Detectors for Cost Effective Applications Lindsey M. Smith1, Sergiy Rozhdestvenskyy2, Israel Mejia2, Manuel Quevedo-Lopez2, and Bruce Gnade1 1Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080 2Department of Materials Science and Engineering, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080

2.30 – 5.00 pm Poster Session SPN, Lobby Area

Impedance measurements of RF pulsed plasmas: Technique and results. L. Overzet1, J. Poulose1 and M.J. Goeckner2 1Department of Electrical Engineering, UTD, 800 W. Campbell Road, Richardson, TX, 75080 2Department of Physics, UTD, 800 W. Campbell Road, Richardson, TX, 75080 Introduction of Nanomaterials to Biological Cells for Development of Anti-Cancer Drug Delivery Vehicle Christine T. Pho, Marais E. Culp, Giridhar R. Akkaraju, and Anton V. Naumov Texas Christian University, Department of Biology, Department of Physics and Astronomy Effect of Acetylene to Hydrogen ratio for Synthesis of Spinnable Carbon Nanotube Forest Using Chemical Vapor Deposition Method in Nitrogen Environment Ye I. Choi, J. H. Choi, Gil S. Lee Department of Electrical Engineering, University of Texas at Dallas, Richardson, TX 75080

Optical Properties of Graphene Oxide under Oxidative and Thermal Treatment Md. Tanvir Hasan, Brian Senger, Price Mulford, Anton V. Naumov Department of Physics and Astronomy, Texas Christian University, TCU Sid Richardson Building, Fort Worth, TX – 76129 The Use of Silicon Nanotube Templates to Direct Perovskite Nanostructure Size R. Gonzalez-Rodriguez,1 N. Arad-Vosk,2 N. Rozenfeld,2 A. Sa’ar,2 J.L. Coffer1 1Department of Chemistry, Texas Christian University, Fort Worth, Texas, 76129 USA; 2Racah Institute of Physics and the Harvey M. Kruger Family Center for Nanoscience and Nanotechnology, the Hebrew University of Jerusalem, Jerusalem 91904, Israel

Structural and Dielectric Properties of Tungsten Substituted Cobalt Ferrite Ceramics R. Gill1, C. Orozco2, C.V. Ramana2 1Department of Chemical Engineering, University of California – Santa Barbara, Santa Barbara, CA, 93106; 2Department of Mechanical Engineering, University of Texas at El Paso, 500 W University Ave, El Paso, TX 79902 The Role of Plant-derived Porous Silicon to Stabilize the Antibacterial Activity of Natural Extracts N. T. Le1, J. R. Kalluri1, A. Loni2, L. T. Canham2, J. L. Coffer1 1Department of Chemistry, Texas Christian University, Fort Worth, TX, 76129, USA; 2pSiMedica Ltd., Malvern Hills Science Park, Geraldine Road, Malvern, Worcestershire WR14 3 SZ, UK Zirconium Carbide Based Self-Healing Ceramics A. Yang, I. Hammood, P. Petry, M. Carl, R.F. Reidy, S.M. Aouadi Department of Materials Science and Engineering, University of North Texas Discovery Park, 3940 N Elm St., Denton, TX, 76207 Plant derived Porous Silicon as a Controlled Drug Delivery Carrier for Photosensitive Drugs/Vitamins J. R Kalluri, J. L Coffer Department of Chemistry, Texas Christian University, Fort Worth, TX-76109 Self-healing Mechanisms in Ag-Nb-O Ternary System Jingjing Gu, Dylan Steiner, JonErik Mogonye, Thomas Scharf, Samir Aouadi University of North Texas, USA

Withdrawn Surface Engineering of Tissue Graft Materials Using Titanium Dioxide Nano-Scaffolds on Titanium Foams J. Barclay, A. Pauer, S. Murguia, M.L. Young, S.M. Aouadi Department of Materials Science and Engineering, University of North Texas, 3940 N Elm St, Denton, TX 76207 Processing and Surface Treatment of TNZT Alloy for Biomedical Implants Madelyn Kramer1, Elodie Leveque1,2, Joshua Barclay1, Nathan Ley1, Samir Aouadi1, Marcus L. Young1 1 Materials Science and Engineering, University of North Texas, Denton, Texas, USA; 2 Physical Measurements, Rouen University, Evreux, France Handheld XRF Spectroscopy Measurements of Silver-plated Cultural Heritage Objects G. Diaz, M. Carl, M. L. Young

Materials Science and Engineering, University of North Texas, Denton, Texas, USA Pulsed Capacitively Coupled Plasma Ignition: PROES and RF-IV Diagnostics J. Poulose1, L. Overzet1, M.J. Goeckner2

1Department of Electrical Engineering, UTD, 800 W. Campbell Road, Richardson, TX, 75080; 2Department of Physics, UTD, 800 W. Campbell Road, Richardson, TX, 75080 Nanoscale Characterization of Transition Metal Dichalcogenide Layered Material HfSe2 Christopher R. Cormier, Rafik Addou, Robert M. Wallace Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson TX, 75080 Effect of Molybdenum Incorporation on the Structure and Dielectric Properties of Cobalt Ferrite Cristian Orozco, Alejandra Melendez, C.V. Ramana Department of Mechanical Engineering, University of Texas at El Paso, 500 W University Ave., El Paso, TX 79968 Polymer/porous silicon (pSi) composite materials for tissue engineering: polymer degradation studies in vitro N. K. Bodiford1, S.J. P. McInnes,2 N.H. Voelcker,2 A. Loni,3 L. T. Canham,3 J. L. Coffer1 1Department of Chemistry, Texas Christian University, Fort Worth, Texas, 76129 USA; 2University of South Australia, GPO Box 2471 South Australia 5001, Australia; 3pSiMedica Ltd, Malvern Hills Science Park, Geraldine Road, Malvern, Worcestershire WR14 3SZ, UK Synthesis of Ternary Transition Metal Silicide Nano-systems using low energy multiple ion implantation Satyabrata Singh, Wcikramaarachchige J. Lakshantha , Bibhudutta Rout Ion Beam Modification and Analysis Laboratory, Department of Physics, University of North Texas, Denton, Texas 76203

Structure and Electronic Properties of Intrinsic and W- and Ti- Doped Gallium Oxide Films Sandeep Manandhar, E.J. Rubio, Gustavo Martinez, C.V. Ramana Department of Mechanical Engineering, University of Texas at El Paso, El Paso, USA

Doping of Yttrium and Molybdenum into tungsten for nuclear applications G. Martinez, C. V. Ramana University of Texas at El Paso, 500 University Avenue, El Paso, TX, 79968

Studies of Surface Photovoltage Transients in Organic Solar Cell Structures C. Harms1, S. Requena1, M. Dusza2, W. Strek3, F. Granek2,4, Y. Strzhemechny1 1Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76109; 2Wroclaw Research Centre EIT+, Stabłowicka Str. 147, 54-066 Wrocław, Poland; 3Institute of Low Temperature and Structure Research, Okólna

Str. 2, 50-422 Wrocław, Poland; 4XTPL, Owczarska Str. 66, 54-020 Wrocław, Poland

Surface Photovoltage Studies of As-Deposited and UV-Treated Polysulfone Thin Films Spin-Cast on Si Wafers A. Dorward1,2, C. Harms1, T. Simon1, S. Requena1, E. Bormashenko3, Y. Strzhemechny1

1 Dept. of Physics & Astronomy, Texas Christian University, TCU Sid Richardson Building, TCU Box 298840, Fort Worth, TX 76129; 2 Dept. of Physics, Washington & Lee University, 204 W Washington St, Lexington, VA 24450; 3 Dept. of Physics, Ariel University, Ari'el, 40700, Israel Structure and Mechanical Properties of W1-yMoyO3 Nanocomposite Thin Film P. Dubey, Gabriel Lopez, Gustavo Martinez, C.V. Ramana Mechanical Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA

2016 REU Fellows, University of Texas at Dallas

Ethylcyclopentadienyltris(dimethylamido)titanium as a halogen-free precursor for the atomic layer deposition of titanium dioxide thin films Thomas M. L’Esperance, Joseph P. Klesko, Aaron Dangerfield, Charith E. Nanayakkara, Charles L. Dezelah*, Ravindra K. Kanjolia*, Yves J. Chabal *SAFC Hitech, Haverhill, Massachusetts 01832, United States Adding Nanoparticles to Plasma Polymerized 3, 4-ethylenedioxythiophene (EDOT) Marlyn G. Torres, Ariell Shield, Keith V. Hernandez, P.L. Stephan Thamban, Amuy V. Walker, Matthew J. Goeckner Synthesis and mechanical characterization of organic nano-structured porous materials. Owen Rettenmaier, Huacheng Gao, Suzie Ghidei, Justin Jiang, Victoria Shiau, Jenny Tan, Sadeq Malakooti, Gitogo Churu, Hongbing Lu Interface Study of AlN on In0.53Ga0.47As Parker Wise, Xiaoye Qin, Robert M. Wallace Study of Selenium-doped CdTe Thin Films Deposited by Closed-spaced Sublimation Zachary Engel, Martha Serna, Jesus Avila, Siddartha Srinivasan Nandagopala Krishnan, Manuel Quevedo-Lopez Seeded chemical bath deposition of Copper Sulfide on organic substrates to produce nanowires Hannah Ramsaywak, Jenny Orbeck, Amy V. Walker

Simulations of Fractal Gels composed of Spherical and Rod-Shaped Particles E. Rose Rosenthal, Lev D. Gelb Simulating Lithium Solvation and Transport in Ionic Liquids Harrison Lee, Amir Taghavi Nasrabadi, Lev D. Gelb Probing surface conductivity in ultra-thin ALD ZnO films Michelle Sugimoto, Eric Mattson, Yuzhi Gao, Zhengning Gao, Parag Banerjee, Yves Chabal

2016 LSAMP Fellows, University of Texas at Dallas

Role of PKMζ in Transition of Acute to Chronic Pain S. Muqueet, S. Megat, T.J.Price Does Personality Predict Episodic Memory throughout the Lifespan? Analysis of the Dallas Lifespan Brain Study Ashley Devoll, Sara Festini, Melissa Rundle, and Denise Park. In Vitro Genome Editing using AAV Mediated CRISPR/Cas9 System Stephanie Dinh, Namrata Kumar, Nigel Abraham, Trieu-Mi Dao, William Stanford, and Jonathan Ploski

2016 PIONEER REU Fellows, University of Texas at Dallas

Phase retrieval comparison: data acquisition, retrieval methods and under-sampling masks. Russell Hart, Yifei Lou Computation of the Alexander and Twisted Alexander Polynomials B. Griffith, P. Smith, M. Dabkowski, A. Eydelzon, V. Ramakrishna Noncommutative Fox Calculus - Computation of Cyclic Branched Covers B. Griffith, P. Smith, M. Dabkowski, A. Eydelzon, V. Ramakrishna

Thursday, August 4th

SPN – HR Training Room Session IV Moderator: C.V. Ramana, University of Texas at El Paso 8.00 – 8.20 am

Contacts on WSe2: Interface Chemistry and Band Alignments Christopher M. Smyth1, Rafik Addou1, Stephen McDonnell2, Jiyoung Kim,1 Christopher L. Hinkle1, Robert M. Wallace1 1Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, TX, 75080, USA 2Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA 22904

8.20 – 8.40 am The Graphene/Co3O4(111) Interface: Implications for other oxides and spintronics O. Olanipekun1, S. Lightbourne1, B. Pollok1, M. Zhang1 , J. A. Kelber1, T. Cheng2, Y. Liu2, W.A Goddard III2 1Department of Chemistry, University of North Texas, 1508 W. Mulberry Street, Denton, TX, 76201 2Materials and process simulation center, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA, 91125

8.40 – 9.00 am Optical properties of graphene oxide and its biological and optoelectronics applications. A. Naumov1, Md. T. Hasan1, M. Culp2, C. Pho1, B. Senger1 1Department of Physics and Astronomy, Texas Christian University, 2800 S University Dr, Fort Worth, TX 76129 2Department of Physics, St. Mary's University of Minnesota, 700 Terrace Heights, Winona, MN 55987

9.00 – 9.20 am Aromatic/Boron Carbide Composites: Emerging Materials for Neutron Detection and More A. Oyelade1, B. Dong1, N. Nandagopal1, E. Echeverria2, P. A. Dowben2, J.A. Kelber1 1Department of Chemistry, University of North Texas, Denton, TX 76203, USA 2Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588

9.20 – 9.40 am A Study of the Controlled Nucleation and Grain Morphology of WSe2 Grown by Molecular Beam Epitaxy R. Yue1, L. A. Walsh1, Y. Nie1, A. Barton1, H. Zhu1, Z. Che1, D. Barrera1, R. Addou1, L. Cheng1, N. Lu1, M. J. Kim1, J. Hsu1, J. Kim1, L. Colombo2, Y. Chabal1, R. M. Wallace1, K. Cho1, C. L. Hinkle1 1Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 2 Texas Instruments, Dallas, Texas

9.40 – 10.00 am

Direct Growth of h-BN(0001) on RuO2 by ALD and MBE

J. Jones, B. Beauclair and J. A. Kelber

Department of Chemistry, University of North Texas, 1504 W. Mulbery St. Denton, TX 76201

10.00 – 10.20 am Coffee Break SPN, lobby area Session V Moderator: L. Overzet, University of Texas at Dallas 10.20 – 10.40 am

Plasma Sterilization S. Patel, A. Gemsheim, L. Overzet, M. Goeckner Department of Electrical Engineering, The University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080

10.40 – 11.40 am Invited Talk Plasma Chemistry at the Air Force: From the Fundamental to the Practical Shaun Ard, Nicholas Shuman, Al Viggiano Air Force Research Laboratory, Kirkland AFB

11.40 am – noon Covalent Nitrogen Doping of 2D Transition Metal Dichalcogenides by Remote N2 Plasma A. Azcatl, X. Qin, C.Zhang, L. Cheng, Q. Wang, N. Lu, M. J. Kim, J. Kim, C. L. Hinkle, Robert M. Wallace

Materials Science and Engineering Department, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75080-3021

noon – 12.20 pm Excitons at interfaces in ellipsometric spectra Stefan Zollner,1 Nuwanjula Samarasingha,1 Cesar Rodriguez,1 Jaime Moya,1 Nalin Fernando,1 Patrick Ponath,2 Kristy Kormondy,2 Alex Demkov,2 Dipayan Pal,3 Aakash Mathur,3 Ajaib Singh,3 Surjendu Dutta,3 Jaya Singhal3 and Sudeshna Chattopadhyay3 1Department of Physics, New Mexico State University, Las Cruces, NM 88007 2Department of Physics, University of Texas at Austin, Austin, TX 78705 3Department of Physics, Indian Institute of Technology, Indore, India

12.20 – 12.40 pm Structural and Dielectric Characterization of Lead-Free Calcium and Cerium BaTiO3 Modified Ceramics Juan A. Duran, Cristian Orozco, C. V. Ramana

Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968, USA

12.40 pm Conference Close

August 3rd, 2016

Abstracts

A Comprehensive CV Simulation and Extraction Tool for Advanced

MOS Device Analysis with Alternative Channels (SiGe and InGaAs)

S. R. M. Anwar1, W. G. Vandenberghe

1 , R. V. Galatage

1, E. M. Vogel

2, and C. L. Hinkle

1

1 Electrical Engineering and Materials Science and Engineering, University of Texas at Dallas,

800 West Campbell Road, Richardson, TX 75080

2 Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Dr., N.W.,

Atlanta, GA 30332

Email: [email protected]

For the next generation of metal oxide semiconductor (MOS) logic devices, various alternative

semiconductor channel materials are being considered to improve device performance [1].

However, there are significant challenges to understanding these new semiconductor-dielectric

interfaces and typical models used for Si-based capacitance-voltage are incorrect for other

materials systems such as InGaAs. For process development of these alternative semiconductors

with high-k gate dielectrics, new tools are needed.

In this work, we present a comprehensive capacitance-voltage (CV) simulation and extraction

tool that that is applicable for a wide range of semiconductors. The model includes non-parabolic

bands, quantum mechanical effects in strong accumulation and inversion, and multiple valleys as

appropriate. The implementation of quantum corrections are a major achievement that allows for

a much more accurate extraction of equivalent oxide thickness, flatband voltage, and interface

state density profiles. These quantum corrections are applied to classical CV calculations

through a modification of the surface potential (instead of using a physical grid or

simultaneously solving a suite of complex equations) [2], allowing our CV simulations and

extractions to be performed orders of magnitude faster than other methods. Quantum mechanical

correction factors are empirically obtained by benchmarking to a full quantum Schrödinger

Poisson (SP) solver developed at UT-Dallas, using a wide range of doping densities and EOTs

with outstanding accuracy. The CV code has been used to analyze experimental MOS structures

of various dielectrics and semiconductors and these results will be presented.

This work is supported by the Semiconductor Research Corporation (SRC) through the Global

Research Collaboration (GRC) and Tokyo Electron Limited (TEL).

References:

[1] D. A. Antoniadis, IBM Journal of Research and Development 50, 363–376 (2006).

[2] E. Vogel, Solid State Electronics 47, 1589-1596 (2003).

In situ surface and interface study of crystalline (3×1)-O on InAs

Xiaoye Qin1, Wei-E Wang2, Mark S. Rodder2, and Robert M. Wallace1,

1Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, USA

2 Advanced Logic Lab, Samsung Semiconductor, Inc, Austin, Texas 78754, USA


InAs has significant potential for future low-power field effect transistors due to a very small direct bulk band gap (Eg = 0.37 eV), as well as light electron and hole effective masses. However, the interface quality limits the development. Minimizing the interface state density Dit becomes essential. Recently, the demonstration of a (3×1) crystalline oxide on InAs shows great potential to improve the high k/InAs interface. However, the stability of the crystalline oxide upon subsequent gate dielectric atomic layer deposition (ALD) procedures is still questionable and lacks direct experimental evidence. In this work, we focus on investigating surface chemical states of the crystalline (3×1)-O and the stability of (3×1)-O upon ALD HfO2. The oxidation behavior of de-capped InAs (100) exposed to O2 gas at different temperatures is investigated in situ with high resolution of monochromatic x-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED). The oxide chemical states and structure change dramatically with the substrate temperature. The (3×1)-O layer on InAs is generated in a temperature range of 290 to 330 °C with a coexistence of In2O and As2O3. The stability of the crystalline oxide upon the atomic layer deposition (ALD) of HfO2 is studied as well. It is found that the generated (3×1) crystalline oxide is stable upon ALD HfO2 growth at 100 °C.

mailto:[email protected]

Atomic Structure of Cross-linked (1 × 2) Rutile TiO2(110) Yaobiao Xia, Ke Zhu, Zhenrong Zhang, and Kenneth T. Park

Department of Physics, Baylor University, Waco, Texas 76798, United States of America


Cross-linked (1 × 2) rutile TiO2(110) has been extensively studied for the photocatalytic applications. However, the atomic structure of this reconstructed surface is still under debate. Employing a carboxylic acid as a probing molecule, we studied the interaction of trimethyl acetic acid (TMAA) with various sites on the surfaces using in situ scanning tunneling microscopy (STM). We compared three specific atomistic models for (1 × 2) reconstructed TiO2(110), Ti2O3, Ti2O, and Ti3O6. The adsorption of TMAA on strands at room temperature strongly supports the Ti2O model for cross-linked (1 × 2) reconstructed TiO2(110).

Selectively removing the carbon overlayer in surface analysis: enhanced information using gas cluster cleaning

C.E. Moffitt1, J. Counsell2

1Kratos Analytical, Inc., 100 Red Schoolhouse Rd., Chesntut Ridge, NY 10977, USA

2Kratos Analytical, Ltd., Wharfside, Trafford Wharf Road, Manchester M171GP, UK


The development of gas cluster ion sources for use in surface characterization has revolutionized the analysis of a host of organic film structures, which was previously impossible. This is due to the ability of the cluster ion to sputter only the very surface of the material, causing no damage to the material beneath the sputtering location. This effect allows organic materials and film systems to be depth profiled for chemical analysis, opening a door to a wide range of relevant materials systems analysis that was previously closed. While the depth profiling of organic film systems is relevant to a wide array of modern applications, the ability of these sources to only remove the organic contaminants from a whole host of samples has revealed the ability to analyze traditional inorganic systems and improve the information attainable in spectroscopy and imaging techniques. This ability to remove the very surface structure, without the damage to the underlying material that is present when using mono-atomic ion etching, also allows structures like metal oxides and glasses to be depth profiled, with much less reduction of oxide structures, or loss of light elements as the etching progresses. Chemical imaging of the sample surfaces is also improved using selective beams, which only have enough energy to remove adsorbed contaminants, especially adsorbed hydrocarbons that are present on the surface of nearly every material exposed to atmosphere. This presentation will discuss data from varied technologies, including mixed metal oxide systems, organic electronics, polymer systems, semiconductor systems and others, and how the use of gas cluster sources have improved the understanding and information attainable.

Super-Resolution Imaging Using Multi-Pulse Pumping of a Long Lived Fluorophore

Sebastian Requenaa, Sangram Rauta,b,c, Hung Doana, Joe Kimballa, Rafal Fudalab,c, Julian

Borejdob,c, Ignacy Gryczynskib,c, Zygmunt Gryczynskia,b,c, and Yuri M. Strzhemechnya

aDept, of Physics & Astronomy, Texas Christian University, TCU Sid Richardson Building, TCU Box 298840, Fort Worth, TX 76129

b Center for Fluorescence Technologies and Nanomedicine Dept. of Molecular Biology and Immunology University of North Texas, Health Science Center 3500 Camp Bowie Blvd, Ft.

Worth, TX 76107

c.Dept. of Molecular Biology & Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., RES-402, Fort Worth, TX 76107


Light microscopy with a resolution significantly below the diffraction limit has attracted tremendous attention allowing for high-resolution optical imaging at the nanoscale. Various super-resolution methods proposed fall into two categories: deterministic techniques such as STED or RESOLFT and stochastic techniques like PALM or STORM. We propose a simple method to achieve super-resolution in far-field fluorescence imaging by the use of controllable bursts of laser pulses that can change the fluorescence signal of long-lived components over one order of magnitude. We demonstrate that two nanoparticles, one labeled with a long-lived dye and another with a short-lived dye, separated by a distance lower than 100 nm, are easily resolved in a single experiment. The proposed method can be used to resolve two nanostructures by labeling them with two different fluorophores; one that is long-lived and one that is short-lived.

Studying Copper Sulfide Chemical Bath Deposition Reactions on Organic Surfaces

J. K. Orbeck1, R.P. Joshi1

, and A.V. Walker1,2

1Department of Chemistry & Biochemistry BE26, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080

2Department of Materials Science & Engineering RL10, University of Texas at Dallas, 800 W.

Campbell Road, Richardson, TX, 75080


Copper sulfide is a highly desirable material for a host of applications including semiconductors and photovoltaics. In this work we deposit copper sulfide onto organic substrates using a chemical bath deposition (CBD) technique. CBD operates as a controlled ion exchange reaction, in this case between a cationic metal and anionic sulfide, and can be achieved in aqueous solutions at low temperatures (i.e. ≤50°C). These gentle conditions make the process energy efficient and ideal for deposition onto organic surfaces including self-assembled monolayers (SAMs). Here copper sulfide was deposited onto alkanethiol SAMs with methyl, hydroxyl and carboxylic acid terminal groups. Copper sulfide has been found to exist in as many as five different phases, therefore its physical properties will depend on the chemical composition of the deposited material. Using XPS, TOFSIMS, and microscopy techniques the composition of copper sulfide and the CBD reaction conditions are explored.

Silicon Nanotubes: A Diverse Platform for Therapeutics and Energy

Jeffery L. Coffer

Department of Chemistry, Texas Christian University, Fort Worth, TX 76129 Email: [email protected]

Silicon Nanotubes (SiNTs) are a form of nanostructured silicon with properties of

potential merit as a biomaterial, including tunable inner and outer diameter, diverse surface functionalization opportunities, along with novel porous sidewall morphologies capable of nanoscale infiltration and release [1]. Any practical applications require the development of practical routes to loading their tubular interior as well as functionalization of the outer surface. In our labs, this has been demonstrated by: (1) the incorporation of superparamagnetic iron oxide nanoparticles (Fe3O4 NPs) into Si NTs possessing different wall thicknesses [2]; (2) an attachment of selected fluorescent probe molecules & primary amine moieties for electrostatic nucleotide coupling; (3) the infiltration and attachment of prominent anticancer therapeutics such as cisplatin into the nanotube interior.

In addition, these same silicon nanotubes have structural elements that render them useful for relevance to photovolatics and battery technologies. For the former, we have investigated the use of hollow semiconducting silicon nanotubes as templates for CH3NH3PbX3 perovskite growth; i.e. viewing the nanotube interior as a nanoscale reaction vessel and thus controlling of perovskite width through nanotube inner diameter [3]. In terms of the latter, the open porous surface structure of these nanotubes suggest relevance to lithium (Li) storage and discharge phenomena associated with battery function [4].

In this presentation, examples of each of the above areas

will be described.

References: [1] X. Huang, R. Gonzalez-Rodriguez, R. Rich, Z. Gryczynski, J.L. Coffer, Chem Comm, 49, 5760-5762 (2013). [2] P. Granitzer, K. Rumpf, R. Gonzalez-Rodriguez, J. L. Coffer and M. Reissner, Nanoscale, 7, 20220-20226 (2015). [3] Roberto Gonzalez-Rodriguez, Neta Arad-Vosk, Naama Rozenfeld, Amir Sa'ar, Jeffery L. Coffer, Small, doi: 10.1002/smll.201601291 (2016). [4] A.T. Tesfaye, R. Gonzalez, J.L. Coffer, T. Djenizian, ACS Appl. Mater. Interfaces, 7, 20495-20498 (2015).

Figure 1. Representative TEM image of SiNTs (scale bar = 200 nm)

Electroless Deposition of Copper on Functionalized SAMs: The Effect of the Reducing Agent on Selective Deposition

A.A. Ellsworth1, A. V. Walker1,2

1Department of Chemistry and Biochemistry, University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX, 75080

2Department of Materials Science & Engineering, University of Texas at Dallas, 800 W.

Campbell Rd., Richardson, TX, 75080


Electroless deposition of metals, in particular copper, has many important technological applications in the fields of microelectronics, wear-resistant coatings, automotive catalysis, and metallization of polymers. The films produced by electroless deposition are continuous and smooth, and can be deposited quickly in ambient conditions, making it a desirable technique compared to other alternatives. Amine-borane reducing agents are a classical component of copper electroless plating systems. Although some effort has been made to study the effect of different amine-boranes on electroless deposition of copper, no work has been done to show the importance of the surface charge in these systems. Here, we show the interaction of a series of amine boranes such as ammonia borane (AB), dimethylamine borane (DMAB), trimethylamine borane (TMAB) with functionalized self-assembled monolayer (SAM) organic surfaces. We demonstrate that charge-charge interactions between the borane compoment of the reducing agent and the surface effect the rate of copper deposition. As reducing agent charge increases, the rate of copper deposition decreases on electronegatively charged surfaces such as an -OH terminated SAM surface compared with a -CH3 terminated surface. We also show that metal complexation with a -COOH SAM surface is affected by depositon pH, allowing for control over deposition rate, film quality, and surface selectivity. This data allows for the optimization of selective deposition of copper on functionalized surfaces, and reveals that using DMAB as a reducing agent at pH 9 is a highly selective system on -OH/-CH3 SAM surfaces producing uniform films at a fast deposition rate with precise control. This work offers insight into reducing agent-surface charge interactions that ultimately contribute to the optimization of nanostructure synthesis such as nanowires, nanopores, and nanochannels on organic surfaces.

The Case for Digital Fabrication at the Atomic Scale (The Inverse Moore’s Law) and Zyvex Labs Approach

J.N. Randall, J.B. Ballard, J.H.G. Owen, E. Fuchs, S. Pryadkin, S. Schmucker and J. Lake

Zyvex Labs, 1301 N. Plano Rd. Richardson Texas 75081


In 1959 Richard Feynman famously stated “I am not afraid to consider the final question as

to whether, ultimately – in the great future – we can arrange the atoms the way we want”. Fifteen years later, Norio Taniguchi defined “Nanotechnology”. Eight years later, the Scanning Tunneling Microscope (STM) was invented. Four years after that, K. Eric Drexler suggested that manufacturing by arranging atoms would be a big deal. Three years after that, Don Eigler used an STM to arrange atoms the way he wanted and spelled out his company’s logo. Eight years after that, Jim Von Ehr founded Zyvex Corp.

This presentation will address what Zyvex Labs sees as the opportunity, in the abstract, for manufacturing where atoms are arranged “where we want them”. An analogy will be drawn with the incredible impact that digital information theory and its implementation with electronics and other technologies. A distinction between analog and digital fabrication will be made. The concept of an Inverse Moore’s Law will be presented.

The specific technological approach that Zyvex Labs is taking to do digital fabrication and realize Atomically Precise Manufacturing (APM) will be presented along with some of the progress we have made. Zyvex Labs’ first commercial research tool that others are using to put atoms where they want them to develop quantum computers will be described. Finally some early prospects for products made with APM will be presented and some options for scaling up Atomically Precise Manufacturing will be discussed.

QUANTUM TRANSPORT AND DIELECTRIC RESPONSE OF NANOMETER SCALE TRANSISTORS

Jingtian Fang

Department of Physics and Astronomy, Vanderbilt University, 2201 West End Ave, Nashville, TN 37235


As transistors, the most basic component of central processing units in all electronic products, are scaling down to the nanometer scale, quantum mechanical effects must be studied to investigate their performance. In this presentation, I will present the ballistic quantum transport properties of silicon nanowire field-effect transistors simulated using an open-boundary-condition and full-band transport formalism [1]. The study shows that ultra-thin-body (< 1nm) silicon nanowires provide the possibility to keep scaling transistors down to 5 nm gate length, owing to the strong quantum-confinement effects and the absence of source-to-drain tunneling. As ultra-thin-body channel materials will be used in nanometer-scale transistors, the dielectric property, such as the static dielectric constant, of nanostructures will be different from their bulk form. I will present a microscopic Poisson equation, derived based on a density-density response function, which can be applied generally to study the dielectric response of any low-dimensional nanostructure. Grapheme nanoribbons are studied as an example and their microscopic dielectric permittivities are demonstrated [2]. The position-dependent permittivity can be applied to solve Schrödinger equation and Poisson equation self-consistently in a more physical way, comparing to the assumption of applying a uniform dielectric constant throughout the channel region and the surrounding oxide region [1]. References: [1] Jingtian Fang et al, J. Appl. Phys. 119, 035701 (2016). [2] Jingtian Fang et al, “Microscopic dielectric permittivities of graphene nanoribbons and graphene”, Phys. Rev. B. Accepted (2016).

Structural and Magnetic properties of ion beam synthesized binary and ternary transition metal silicides

Wcikramaarachchige J. Lakshantha 1, Satyabrata Singh1 and Bibhudutta Rout1

1 Ion Beam Modification and Analysis Laboratory, Department of Physics,

University of North Texas, Denton, Texas 76203 Email: [email protected]

The interests in transition metal silicide systems are triggered by their potential use in advanced silicon based opto-electronic devices. In addition, ternary metal silicides have been by far less studied than their binary counterparts despite the fact that they have interesting magnetic and electronic properties. In this study, we have investigated ion beam synthesis of Fe-Si binary alloys and Fe-Co-Si ternary alloys thin films and nano-structures and their structural and magnetic properties. Since the ion implantation is a dynamic process, simulation models incorporating dynamic changes in the target layer composition were used in these studies to predict distribution of the implanted ions and target atoms and compared with the experimental result. The Fe- ion implantation was carried with the Si substrate placed under an external magnetic field, which was perpendicular to the incoming ion direction and parallel to the substrate surface, which is much stronger compared to the earth’s magnetic field. External magnetic field stimulates the formation of magnetic phase centers in the substrate. X-ray diffraction (XRD) results showed formation of ferromagnetic Fe3Si phase in the Si matrix after annealing the implanted sample at 500 oC for 60 minutes. In addition, X-ray photoelectron spectra (XPS) provide further evidence for ferromagnetic metallic behavior of Fe3Si in the substrate. The ternary Fe(1-x)CoxSi B20 phase was formed by implanting Fe and Co consecutively into Si substrate at 50 keV energy with the presence of an external magnetic field. The samples were subsequently annealed in vacuum at 500 oC for 60 minutes. XRD and XPS characterization results indicate the formation of Fe(1-x)CoxSi B20 structures in the implanted layer with a lattice parameter of 0.453±0.003 nm. Magnetic property measurements indicate a typical diamagnetic response for the as-implanted sample with a weak ferromagnetic contribution. This diamagnetic behavior comes from the silicon substrate and the implanted Fe and Co forms the ferromagnetic structures with the implantation process to contribute the weak ferromagnetic contribution in the as-implanted sample. Further, magnetization of the as-implanted sample does not show a strong temperature dependence, which indicates strong diamagnetic behavior in the sample. After the heat treatment, the sample shows ferromagnetic behavior at 3 K and 300 K temperatures. Further results shows coercivity which corresponds to typical ferromagnetic materials. Studies shows that the Fe(1-x)CoxSi B20 phase has helical magnetic ordering. However, our experimental observations contradict previous claims on the Fe(1-x)CoxSi B20 phase structure by showing coercivity values. Moreover, a magnetic phase transitions was observed around ~ 50 K.

Improvements for Thin Film Solid State Neutron Detectors for Cost Effective Applications

Lindsey M. Smith1, Sergiy Rozhdestvenskyy2, Israel Mejia2, Manuel Quevedo-Lopez2, and

Bruce Gnade1

1Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080

2Department of Materials Science and Engineering, University of Texas at Dallas, 800 W.

Campbell Road, Richardson, TX, 75080


Solid state thermal neutron detectors offer a cost effective alternative to 3He based neutron detectors. Solid state neutron detectors consist of a neutron conversion layer and a charged particle sensing diode layer. The conversion layer converts neutrons into charged particles which are sensed in the charged particle sensing region (Figure 1). In this work, thin film CdTe is optimized to be a gamma-ray insensitive charged particle sensor with high charge collection efficiency. A cost effective conversion film made from a 10B4C/polymer composite is fabricated that can be deposited by the simple spin coating method. An experimental setup for neutron detection is demonstrated for the first time at UTD. Using detector design strategies such as a hydrogen dense backing layer, intrinsic thermal neutron efficiencies of up to 16% are reported while maintaining a gamma discrimination that is greater than 10-6.

Fig 1. . Diagram showing principles of solid state neutron detector

August 3rd, 2016

Posters

Impedance measurements of RF pulsed plasmas: Technique and

results.

L. Overzet1, J. Poulose

1 and M.J. Goeckner

2

1Department of Electrical Engineering, UTD, 800 W. Campbell Road, Richardson, TX, 75080

21

Department of Physics, UTD, 800 W. Campbell Road, Richardson, TX, 75080


So-called “pulsed plasmas” turn on and off repeatedly as the radio-frequency source power is

turned on and off. The ignition of the plasma at each turn-on induces quick impedance changes

as the plasma sheath and bulk reform because the bulk becomes conductive and the sheath

becomes capacitive. These quick changes in the plasma impedance can cause apparent changes

in the instantaneous RF voltage and current frequencies despite the fact that the applied

frequency is fixed. In this presentation, we describe how one can detect a time dependent

frequency on an RF cycle by cycle basis as well as use a Fast Fourier Transform to determine the

time dependent voltage, current and impedance. The methods are applied to time resolved

studies of plasma impedance and frequency during pulsed plasma ignition in both electropositive

(Ar) and electronegative (CF4/O2/Ar) gas mixtures.

This material is based upon work supported by the Applied Materials and LAM Research under

an NSF IUCRC Center.

Introduction of Nanomaterials to Biological Cells for Development of Anti-Cancer Drug Delivery Vehicle

Christine T. Pho, Marais E. Culp, Giridhar R. Akkaraju, and Anton V. Naumov

Texas Christian University, Department of Biology, Department of Physics and Astronomy


Due to their unique physical properties, carbon nanotubes and graphene oxide have high potential as drug-delivery vehicles. Carbon nanotubes and graphene oxide emit fluorescence that allows us to image and track these nanomaterials inside living cells in the red and near-infrared, where background autofluorescence is minimal. This makes them ideal for biomedical imaging. Through fluorescence microscopy we have imaged the fluorescence of graphene oxide and its accumulation in cells (fig. 1.) Furthermore, our cytotoxicity studies of carbon nanotubes and graphene oxide show that they both have low toxicity in human embryonic kidney cells, which make them good candidates for drug delivery. In the future, we will continue to investigate and develop these two nanomaterials as novel drug delivery vehicles for the advancement of anti-cancer therapy and human health.

Fig. 1. Fluorescence of Graphene Oxide in HeLa Cells

Effect of Acetylene to Hydrogen ratio for Synthesis of Spinnable

Carbon Nanotube Forest Using Chemical Vapor Deposition Method

in Nitrogen Environment

Ye I. Choi, J. H. Choi, and Gil S. Lee*

Department of Electrical Engineering, University of Texas at Dallas, Richardson, TX 75080


Many studies have grown carbon nanotubes in forest form on a substrate with metal

nanoparticles. Also, carbon nanotubes can be directly spun from the forest, known as spinnable

CNT forest. Typically, the growth process of CNT forest contains a carbon source gas and

carrier gas. For the carbon source gas, many groups use acetylene, methane, and ethylene.

Famous carrier gas are either helium or argon gas. However, both helium and argon are infamous

for its high market price. Even though, few studies have shown that spinnable CNT forest can be

synthesized with nitrogen as a carrier gas, it still requires more information for it to be

commercialized. [1]

In this study, we have grown spinnable CNT forest using chemical vapor deposition (CVD)

method for the growth process. At high temperature (780˚C), mixture of gases (N2, H2, and C2H2)

was applied to the substrate that has thin iron layer (2~3nm) deposited by electron beam

deposition tool. We have tested how the ratio of acetylene and hydrogen flow rate effects the

spinnable CNT forest growth. During the process, hydrogen flow rate was 150 sccm, and

acetylene flow rate varied from 50 sccm ~ 450 sccm (ratio of .333 ~ 4.00). Figure 1 shows the

directly spun CNT thread (over 1m) from the forest grown in nitrogen environment.

Figure 1- Directly spun CNT thread. The length measured is over 1m.

References:

[1] IEEE Transactions on Nanotechnology, 13, no. 2, 349-356 (2014).

Optical Properties of Graphene Oxide under Oxidative and Thermal Treatment

Md. Tanvir Hasan, Brian Senger, Price Mulford, Anton V. Naumov

Department of Physics and Astronomy, Texas Christian University, TCU Sid Richardson Building, Fort Worth, TX - 76129


Graphene possesses a number of advantageous properties, however, does not exhibit optical emission, which limits its use in optoelectronics applications. Unlike graphene, its functional derivative: graphene oxide (GO) exhibits active optical response. Influence of oxidative and thermal treatment on GO optical properties was observed. Oxidative ozone treatment of reduced graphene oxide (RGO) produced the change in color and absorption spectra of samples, indicative of transforming RGO into GO. Upon ozone treatment, a broad fluorescence spectrum was observed in the visible previously not detected for RGO. Fluorescence signal measured continuously for the sample ozone-treated inside the spectrometer showed a gradual increase with processing time. Temperature treatment of GO up to 95ºC has shown a reversal of optical signatures induced by ozonation, including fluorescence quenching and darkening of the sample. Also, timed ozone treatment of single layered solid GO showed a significant shift in the emission spectrum which gives us the power to control the energy bandgap of GO samples for optoelectronics and sensing applications. These optical changes help elucidate electronic origins of emission in graphene oxide. Theoretical modeling of GO based on our experimental data showed localization of the electronic density in the graphitic regions surrounded by functional groups; that may act as origins for emission.

The Use of Silicon Nanotube Templates to Direct Perovskite Nanostructure Size

R. Gonzalez-Rodriguez,1 N. Arad-Vosk,2 N. Rozenfeld,2 A. Sa’ar,2 and J. L. Coffer1

1Department of Chemistry, Texas Christian University, Fort Worth, Texas, 76129 USA

2Racah Institute of Physics and the Harvey M. Kruger Family Center for Nanoscience and Nanotechnology, the Hebrew University of Jerusalem, Jerusalem 91904, Israel.


A class of alkyl ammonium lead halide structures that readily crystallize as perovskite phases of the generic formula RNH3PbX3 have been discovered, and their relative ease of crystallization and formation into robust films have led to the development of an exciting new class of photovoltaic and lasing platforms. To our knowledge, however, synthetic methods that permit an evaluation of the fundamental size dependent properties with the requisite level of control of any of these perovskite structures have not yet been achieved. In this presentation, we demonstrate the formation of perovskite (CH3NH3PbI3) nanotstructures of 30 nm, 70 nm and 200 nm whose width is dictated by the inner diameter of a silicon nanotube (Si NT) template. Structural characterization of these structures is achieved via a combination of electron microscopies (SEM, TEM, and high resolution lattice imaging) with associated energy dispersive elemental analysis. After structural characterization, the photophysical properties of these perovskite nanostructures, in terms of optical absorption and photoluminescence (PL) as a function of temperature, are evaluated. Spectroscopic comparisons with relatively larger one-dimensional microwires of the same composition are also carried out. We seek to interrogate not only the presence of size dependent shifts in absorption/emission features associated with a given perovskite structure, but also the effects of physical confinement on possible size-dependent phase behavior of these one dimensional semiconductors. The PL and corresponding absorption edge shows a size dependent behavior consistent with a simple quantum confinement model. Further investigations of CH3NH3PbI3 with other feature sizes, along with more detailed photophysical experiments, are in progress. We believe perovskites of this dimension hold great promise in photonics and photovoltaic systems. References: [1] Gonzalez-Rodriguez, R., Arad-Vosk, N., Rozenfeld, N., Sa'ar, A. and Coffer, J. L. , Small. (2016), doi: 10.1002/smll.201601291.

Structural and Dielectric Properties of Tungsten Substituted Cobalt

Ferrite Ceramics

R. Gill1, C. Orozco

2 and C.V. Ramana

2

1Department of Chemical Engineering, University of California – Santa Barbara, Santa Barbara,

CA, 93106

2Department of Mechanical Engineering, University of Texas at El Paso, 500 W University Ave,

El Paso, TX 79902


Cobalt ferrite (referred to CFO) has been widely used in many applications including

information storage systems, magnetic drug delivery, telecommunications, electronic and

magneto-electronic devices. CFO is considered to be one of the most significant magnetic

material that has good mechanical stability, low thermal conductivity, high dielectric constant,

tunable magnetic properties, and high coercivity. Recent observation of coexistence of both

magnetic ordering and ferroelectricity with giant dielectric constant in doped CFO motivated us

to study the effect of tungsten incorporation as a part of our ongoing work on transition-metal-

doped CFO materials. CoFe2-xWxO4 ceramics were prepared using standard high-temperature

ceramics processing method. W content (x) was varied in the range of 0.0-0.3. The effect of W-

substitution on the structure and dielectric properties of CFO was investigated. The crystal

structure, surface morphology, chemical composition and dielectric properties of CoFe2-xWxO4

ceramics were evaluated using an array of analytical techniques. The results indicate that

dielectric properties of CoFe2-xWxO4 ceramics can be tuned by controlling the W-content and

processing conditions.

The Role of Plant-derived Porous Silicon to Stabilize the Antibacterial Activity of Natural Extracts

N. T. Le1, J. R. Kalluri1, A. Loni2, L. T. Canham2, J. L. Coffer1

1Department of Chemistry, Texas Christian University, Fort Worth, TX, 76129, USA. 2pSiMedica Ltd., Malvern Hills Science Park, Geraldine Road, Malvern, Worcestershire WR14 3

SZ, UK.


The biocompatibility of nanostructured porous silicon (pSi) has enabled extensive investigations in various biomedical areas including biosensing and drug delivery. In terms of fabrication routes to this material, biogenic pSi derived from plants is a very appealing option owing to the low cost of starting materials and the use of non-hazardous reagents. In particular, our group has demonstrated the ability of plant-derived pSi to serve as a matrix for stabilizing the naturally active but otherwise metastable therapeutic agents. In the studies reported here, the properties of pSi loaded with garlic extract containing the bioactive compound allicin are evaluated.

The pSi utilized in our work was synthesized from the magnesiothermic reduction of silica extracted from Tabasheer powder, which is obtained from the nodal joint of the Bambusae plant. The formation of pSi was confirmed by a combination of techniques: X-ray Diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. For drug loading, garlic bulbs were mechanically crushed to obtain fresh garlic oil, which was then loaded into Tabasheer-derived pSi. Thermogravimetric analysis showed the amount of the extract was 53.1 (± 2.2) % wt of the loaded material. For characterization of the antibacterial activity of the extract-loaded pSi, agar disc diffusion and turbidity assays against Staphyloccocus aureus (S. aureus) were performed. It is demonstrated that pSi has the ability to stabilize the activity of garlic extract for up to 1 month when the loaded samples were stored under refrigerated conditions.

Additional comparisons of this pSi versus oxidized porous silica (pSiO2) derived from the same plant source were made to evaluate the ability of a given matrix to protect the therapeutic agents under light irradiation. After 24 h intervals of exposure to UV light (365 nm), the greater antibacterial activity of the extract-loaded Tabasheer-derived pSi confirms it is a better choice for stabilizing the active components in the garlic extract compared to pSiO2.

References:

[1] L. Batchelor, A. Loni, L.T. Canham, M. Hasan, and J.L. Coffer, Silicon, 4, 259-266 (2012). [2] L.D. Lawson and Z.J. Wang, J. Agric. Food Chem. 53, 1974−1983 (2005).

Zirconium Carbide Based Self-Healing Ceramics

A. Yang1, I. Hammood

1, P. Petry

1, M. Carl

1, R.F. Reidy

1, and S.M. Aouadi

1

1Department of Materials Science and Engineering, University of North Texas Discovery Park,

3940 N Elm St., Denton, TX, 76207


Self-healing ceramics are novel materials that have the ability to restore mechanical properties of

cracked materials through annealing. This research focuses on the self-healing ability of

zirconium carbide based nano-composites. Zirconium carbide is a stable compound and is

commonly used in harsh environments, such as those encountered in space and aerospace

applications. A Vickers Hardness Tester was used to inflict small diamond shaped cracks in the

sample. The sample was then self-healed through heating at 1100°C for four hours and analyzed

using scanning electron microcopy and x-ray diffraction to determine the chemical and structural

changes that occurred at the crack site. Three sample compositions were tested for their self-

healing ability in this study, namely ZrC/SiC/Y2O3, ZrC/Al2O3/Y2O3, and ZrC/Si3N4/Y2O3.

Sintered and unsintered samples of the same composition were compared to each other. The

sintered samples were heated to 1000°C for three hours. The introduction of Fe2O3 to

ZrC/SiC/Y2O3 interestingly was found to yield tubular whiskers when sintered.

Plant derived Porous Silicon as a Controlled Drug Delivery Carrier for Photosensitive Drugs/Vitamins

J. R Kalluri1, J. L Coffer1

1Department of Chemistry, Texas Christian University, Fort Worth, TX-76109


Protection of natural product based therapeutically active components is a key

challenge in the pharmaceutical industry. Photosensitive vitamins fall into such a category, where long-term storage with retention of stability is required. Most of the existing microencapsulation techniques offer stabilization of active ingredients for controlled release and processibility. One new option, the use of biodegradable mesoporous materials (silicon/silica) with high surface areas, offer nanoentrapment of active components which further improves in principle the bioavailability of components possessing poor aqueous solubility. Furthermore, our group has extensively investigated new ‘green’ routes to the formation of mesoporous silicon using a chemical extraction of silica from silicon accumulator plants followed by a magnesiothermic reduction into porous silicon.

In this presentation we will discuss the fabrication route developed to prepare

nanostructured porous silicon (pSi) from silicon accumulator plants, along with studies on the incorporation and controlled release of cholecalciferol (Vitamin D3), a fat soluble vitamin into/from this matrix. We compare the release profiles of different loading protocols for this system to entrap the drug within the carrier, minimize the burst release, and achieve sustained therapeutic delivery.

Self-healing Mechanisms in Ag-Nb-O Ternary System

Jingjing Gu; University of North Texas, USA

Dylan Steiner; University of North Texas, USA

JonErik Mogonye; University of North Texas, USA

Thomas Scharf; University of North Texas, USA

Samir Aouadi; University of North Texas, USA

We seek to gain new insights into the fundamental deformation mechanisms of self-healing

oxides in response to thermal and/or mechanical stimuli. Model systems that will be investigated

are binary oxides that are at least partially restored through the extrinsic or intrinsic addition of

silver or silver oxide nanoscale elemental inclusions that form ternary oxides (e.g., Nb2O5 + Ag

→ AgNbO3). The selected oxides were produced in bulk (sintering). A surface crack was created

and a healing agent was added intrinsically or extrinsically. The sample was annealed to

stimulate the self-healing process by forming a ternary oxide in the crack region. X-ray

diffraction was used to explore phase evolution, chemical compositions, and structural properties

of the sintered and sputtered samples before and after annealing. The composition of the sintered

sample was verified by Raman spectra at the inside and outside of the notch. SEM equipped with

EDS was used to investigate the chemical and morphological properties of the fracture surface.



Processing and Surface Treatment of TNZT Alloy for Biomedical

Implants

Madelyn Kramer1, Elodie Leveque

1,2, Joshua Barclay

1, Nathan Ley

1, Samir Aouadi

1, and

Marcus L. Young1

1 Materials Science and Engineering, University of North Texas, Denton, Texas, USA

2 Physical Measurements, Rouen University, Evreux, France


In this study, a TNZT alloy composed of Ti-35Nb-7Zr-5Ta in at.% was tested for its ability to

grow nano-scaffolds on the surface for biomedical applications such as implant devices. The

TNZT alloy was made by vacuum arc melting; and then rolled into a plate where it was

subsequently sectioned and cut. The samples were polished flat and underwent hydrothermal

treatments to grow nano-scaffolds of oxides on the surface. TiO2 nano-scaffolds were grown

hydrothermally at varying times using TiO2 powder and a NaOH solution at 180°C. These

TNZT nano-scaffolds exhibited different morphologies based on duration in solution. The

TNZT also produced Nb2O5 nano-scaffolds from a hydrothermal reaction in varying alkaline

solutions: KOH at 170°C and NaOH at 60°C. The TNZT and the nano-scaffolds were

characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM),

X-ray diffraction (XRD) and Raman spectroscopy. The nano-scaffolds will be further examined

in simulated body fluid to assess their biomedical compatibility.

Handheld XRF Spectroscopy Measurements of Silver-plated

Cultural Heritage Objects

G. Diaz1, M. Carl

1, and M. L. Young

1

1Materials Science and Engineering, University of North Texas, Denton, Texas, USA


Sometimes referred to as “The Curator’s Dream Instrument,” handheld X-ray fluorescence

(XRF) spectroscopy has heralded a new age in non-invasive art and archeology analysis

techniques. Although it does a great job of identifying which elements are present on the surface,

most cultural heritage objects are multilayered and exhibit a variable composition with location,

making data analysis challenging. Knowledge of what lies in the layers can elucidate the object’s

method of production, origin, and extent of damage if present. In this presentation, we discuss

XRF spectroscopy measurements of some common alloys with varying thicknesses of silver

plating at different tube settings, in an effort to find the relationship between the increase in

silver on the surface and attenuation of the signal and to explore the limits of detection and

quantification of the XRF. ARTAX and PyMCA, an open-source fundamental parameters

software, are utilized for data acquisition, processing, and calibration. The results from this study

provide a method to nondestructively measure the thickness of the silver layer and the elemental

composition of the underlying alloy of cultural heritage objects with reasonable accuracy.


Pulsed Capacitively Coupled Plasma Ignition: PROES and RF-IV

Diagnostics

J. Poulose1, L. Overzet

1 and M.J. Goeckner

2

1Department of Electrical Engineering, UTD, 800 W. Campbell Road, Richardson, TX, 75080

21

Department of Physics, UTD, 800 W. Campbell Road, Richardson, TX, 75080


Pulsed plasma ignition induces rapid changes to the electron energy distribution function. These

transitions are of particular interest in the application of etching and deposition of

semiconductors. In this article we report temporally and spatially resolved measurements of the

optical emission intensity and RF current and voltage for 1 kHz pulsed plasmas in both

electropositive (Ar) and electronegative (CF4/O2/Ar) gas mixtures. This allows us to develop a

better understanding of the transients during the beginning and end of the powered component of

the RF pulse. We are able show the development of the plasma sheath early in the pulse by

combining phase resolved optical emission intensity measurements with measurements of the

radio frequency power delivery. In the electronegative discharge we find that the sheath width is

minuscule early in the pulse but then expands rapidly. The rapid expansion results in a wave like

phenomenon with negative ions bouncing between the growing sheaths.

This material is based upon work supported by Applied Materials, LAM Research and the

National Science Foundation under Grant IIP1338917.

Preference: contributed oral

Nanoscale Characterization of Transition Metal Dichalcogenide

Layered Material HfSe2

Christopher R. Cormier, Rafik Addou, and Robert M. Wallace

Department of Materials Science and Engineering, The University of Texas at Dallas

Richardson TX, 75080


Transition metal dichalcogenides (TMDs) are materials of the form MX2, where M is a transition

metal (Mo, W, Hf, Re, Sn, etc.) and X is either S, Se, or Te. The TMDs of interest are two-

dimensional layered structures with tunable electrical properties. Because of such properties,

TMDs are being studied for use in optical and electronic applications, including Si replacement

in the fabrication of transistors. [1,2] According to the density functional theory, HfSe2 has

among the highest room-temperature mobility of the TMDs, with a finite band-gap [2], making it

attractive for device applications. Only a few studies on the molecular beam epitaxy (MBE)

growth and the intrinsic properties of HfSe2 have been carried out. [3,4] Here, we have studied

the surface of commercial HfSe2 crystals, grown by chemical vapor transport (CVT). By X-Ray

Photoelectron Spectroscopy (XPS), we observe that the HfSe2 surface tends to rapidly oxidize in

air in comparison to other 2D materials such as graphite and MoS2. With 10 minutes of air

exposure, a noticeable shoulder in the Hf 4f core level appears, corresponding to hafnium oxide.

With 1 minute of air exposure, the O 1s signal was present, but the HfOx was below the XPS

limit of detection. Using the surface exposed in air for 1 minute, we performed STM and STS

measurements. The STM images show a high density of defects corresponding to dark holes of

~3-6 nm in width and ~0.3-2 nm in depth. Both atomic resolution STM and transmission electron

microscopy (TEM) images show the expected octahedral 1T structure with a unit cell ~0.38 nm.

The STS measurements show that HfSe2 is an n-type semiconductor with a band gap of ~1.1 eV.

This work was supported by the Southwest Academy on Nanoelectronics (SWAN) center

sponsored by the Nanoelectronic Research Initiative and the Erik Jonsson Distinguished Chair.

___

References:

[1] G. Fiori et al. Nature Nanotechnol. 9, 768–779 (2014)

[2] W. Zhang et al. Nano Res. 7, 1731-1737 (2014).

[3] R. Yue, A. Barton, et al. ACS Nano. 9, 474-480 (2015).

[4] K. E. Aretouli, et al. App. Phys. Lett. 106, 143105 (2015).

Preference: Poster

Polymer/porous silicon (pSi) composite materials for tissue engineering: polymer degradation studies in vitro

N. K. Bodiford1, S.J. P. McInnes,2 N.H. Voelcker,2 A. Loni,3 L. T. Canham,3 J. L. Coffer1

1Department of Chemistry, Texas Christian University, Fort Worth, Texas, 76129 USA

2University of South Australia, GPO Box 2471 South Australia 5001, Australia 3pSiMedica Ltd, Malvern Hills Science Park, Geraldine Road, Malvern, Worcestershire WR14

3SZ, UK

Email:[email protected]

The combination of inorganic porous silicon (pSi) and flexible biocompatible polymers has been shown to yield more beneficial hybrid scaffolds for tissue engineering.1 pSi has a variety of tunable properties including pore size, surface chemistry, and non-toxic degradation products.2 The addition of a flexible polymer component permits the resulting composite to easily conform to any shape of the actual site of an injury/disease. This study focuses on composites of pSi with the FDA approved polymer polycaprolactone (PCL). In particular, the degradation behavior of the polymer as a function of its morphology and the effect of pSi on polymer degradation has been evaluated.

Two types of polymer scaffolds were prepared: 1) non-woven polymer fibers 10 μm in diameter prepared by an electrospinning method; and 2) solid films based on fibers fused at a temperature of 65-80oC. Two types of pSi surfaces were selected to prepare the composites; oxidized pSi with particle size of ~30 μm and as-prepared hydride-terminated pSi with a particle size of ~200 μm. pSi particles were embedded into a given PCL structure resulting in two categories of samples: pSi/PCL fibers and pSi/PCL films. All samples were incubated at 37oC in three types of solutions: cell culture medium, phosphate-buffered saline (PBS), and distilled water. Composite evolution after 5 weeks degradation in vitro was examined by weight loss, polymer crystallinity using differential scanning calorimetry (DSC), and surface morphology/composition (SEM/EDX).

For these pSi/PCL composites, it is found that the polymer structure evolves over time with an increase in % crystallinity for the PCL in both fiber and film composites. By the end of the degradation period pSi/PCL fiber composites become brittle and fragile, whereas pSi/PCL solid film composites remain intact. In the present composite system, pSi has no significant effect on PCL polymer degradation rate and crystallinity over time.

References: [1] J.L. Coffer, “Porous Silicon as a Tissue Engineering Scaffold,” in Handbook of Porous Silicon, L.T. Canham, Ed., Springer. (2014). [2] S.H.C. Anderson, H. Elliot, D.J. Wallis, L.T. Canham, J.J. Powell, Physica Status Solidi a. 197 (2), 331-335 (2003).

Synthesis of Ternary Transition Metal Silicide Nano-systems using low energy multiple ion implantation

Satyabrata Singh 1, Wcikramaarachchige J. Lakshantha 1, and Bibhudutta Rout 1

1 Ion Beam Modification and Analysis Laboratory, Department of Physics,

University of North Texas, Denton, Texas 76203 Email: [email protected]

Ternary intermetallic compounds (e.g. Fe, Co, Ni, Mn, Ga, Si, etc.) can form interesting structures such as Heusler alloys. Due to their unique crystallographic structures and chemical phases, the Heusler alloys exhibit remarkable magnetic, electronic, and thermal properties. By reducing the alloy film dimensions to nanoscale, significant improvements have been achieved in the thermo-electric, spintronic, and ferromagnetic shape memory properties of these alloys. Various Heusler alloy thin films, involving Fe, Co and Si, have been grown as bulk materials or as thin films on the surfaces of GaAs and MgO surfaces using sputtering and chemical vapor deposition techniques. However, there is not much research done on the synthesis of self-assembled ternary metal-silicides or Heusler alloy nano-systems. Recently, because of proven industrial technology based on silicon, there is a greater desire for the growth of the Heusler compounds on the Si surfaces. Among the well-known synthesis techniques to form or to modify the composition and physical properties of thin films, low energy ion implantation (< 50 keV) is shown to be a very powerful technique. In this project, we have implanted consecutively Fe and Co ions, both at 50 keV into commercially available Si nanowires grown on Si wafer to synthesize ternary metal silicide nano-systems. Since the ion implantation is a dynamic process, simulation models incorporating dynamic changes in the target layer compositions are used in this study to predict redistribution of the implanted ions and target atoms. The simulation shows that for 50 keV Fe ion implanted in Si, the Fe concentration is seen to be saturated at a fluence of 1.2×1017 atoms/cm2 and higher. Then, subsequent simulation are performed taking the output data from the first simulation to find the saturation fluence for the Co implanted in to the Fe-Si nanowire system. It shows that the saturation fluence for the Co ions is the same as that for Fe ions. The results of these simulations show that for Si nanowires, having a diameter of 200 nm and irradiated with 50 keV Fe and Co, will facilitate formation of a ternary alloy nanowire system of a diameter ~110 nm due to the sputtering caused by the implanted ions. The implanted samples were annealed at different temperatures (500 – 800 °C) to form various phases of Co-Fe-Si ternary-silicide alloy nano-systems. We will report the structural and chemical composition of these ternary alloy nanostructures.

Structure and Electronic Properties of Intrinsic and W- and Ti- Doped Gallium Oxide Films

Sandeep Manandhar, E.J. Rubio, Gustavo Martinez and C.V. Ramana

Department of Mechanical Engineering, University of Texas at El Paso, El Paso, USA


Gallium oxide (Ga2O3), the stable oxide of gallium, finds attractive applications in luminescent phosphors, high temperature sensors, antireflection coatings, and solar cells. Ga2O3 has been recognized as a deep ultraviolet transparent conducting oxide (UV–TCO), which makes the material a potential candidate for transparent electrode applications in UV optoelectronics. While conventional transparent oxides are opaque in the UV region due to small band gap (~3 eV), Ga2O3 exhibits a wide band gap (~5 eV) and deep transparency to the UV region. In the present work, a detailed analysis of growth behavior, microstructure, and optical properties of intrinsic and metal doped β- Ga2O3 films grown by sputter deposition is performed. Tungsten (W) and titanium (Ti) doped Ga2O3 thin films were deposited on Si(100) and quartz substrates by keeping the growth temperature constant at 500 ̊C and varying the amount of W/Ti. The characteristic analysis of the samples was performed employing Rutherford Backscattering, X-ray diffraction, Spectrophotometry and Ellipsometry. The detailed analysis of W/Ti-induced electronic structure changes and associated mechanism will be presented based on the data obtained from optical spectrophotometry and spectroscopic ellipsometry measurements.

Studies of Surface Photovoltage Transients in Organic Solar Cell Structures

C. Harms1, S. Requena1, M. Dusza2, W. Strek3, F. Granek2,4, Y. Strzhemechny1

1Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX, 76109

2Wroclaw Research Centre EIT+, Stabłowicka Str. 147, 54-066 Wrocław, Poland 3Institute of Low Temperature and Structure Research, Okólna Str. 2, 50-422 Wrocław, Poland

4XTPL, Owczarska Str. 66, 54-020 Wrocław, Poland


The lower production costs of organic photovoltaic (OPV) solar cells vs. traditional inorganic architectures could provide a more cost-effective alternative for the solar power industry. We studied layered OPV samples of P3HT:PCBM/ZnO/ITO/glass employing surface photovoltage (SPV) measurements. The SPV experiments were performed via the Kelvin probe approach in a vacuum chamber filled with a 100% nitrogen gas at atmospheric pressure. The data was collected both as a function of time for a polychromatic illumination and as a function of photon energy for a monochromatic illumination. ZnO/ITO/glass and ITO/glass structures were also probed as control samples. The P3HT:PCBM/ZnO/ITO/glass specimens were synthesized with variations of growth/deposition/processing temperatures of both P3HT:PCBM and ZnO. The addition and variations of synthesis conditions of the active layer produced significant changes in the observed “light-on” and “light-off” SPV transients, which revealed fast and slow charge recombination processes (in contrast with, e.g., the ZnO/ITO/glass samples yielding only one “standard” recombination time). Presence of the active layer and its growth conditions also dramatically affected the SPV spectroscopy data. Furthermore, both the transient and spectral SPV results were dependent on the growth/deposition conditions of the ZnO layers. The multiple processes on different timescales indicate the presence of several pathways for surface/interface charge recombination. Whether the long-term recession of the voltage-against-time values is a factor of the specimens or due to atmospheric adsorption or some other cause is yet to be determined and requires further study.

Surface Photovoltage Studies of As-Deposited and UV-Treated Polysulfone Thin Films Spin-Cast on Si Wafers

A. Dorward1,2, C. Harms1, T. Simon1, S. Requena1, E. Bormashenko3, Y. Strzhemechny1

1 Dept. of Physics & Astronomy, Texas Christian University, TCU Sid Richardson Building, TCU Box 298840, Fort Worth, TX 76129

2 Dept. of Physics, Washington & Lee University, 204 W Washington St, Lexington, VA 24450

3 Dept. of Physics, Ariel University, Ari'el, 40700, Israel


Polysulfone, normally hydrophobic, becomes hydrophilic when exposed to UV radiation. However, the effects of polysulfone electronic surface properties on hydrophilicity are largely unknown. This knowledge could be helpful in understanding the behavior of polysulfone on the nanoscale for emerging applications in microfluidics and biophysics. We deposited polysulfone thin films by spin-casting polysulfone/chloroform solutions onto silicon wafers. To probe the surface optoelectronic properties of polysulfone, we ran surface photovoltage (SPV) spectroscopy and SPV transient experiments on these thin films, some of which were also exposed to UV radiation. Bare Si samples were used for similar experiments as control specimens. It was found that the addition of polysulfone not only significantly enhances the overall SPV signal yield, but also modifies both the SPV transients and the SPV spectra. For example, the “fast” component of the SPV “light-on” transient reverses its polarity upon deposition of polysulfone. Furthermore, addition of polysulfone thin films significantly rearranges the 1.1 – 1.5 eV spectral range. We also discuss the effects of UV irradiation on the properties of the studied samples.

Structure and Mechanical Properties of W1-yMoyO3 Nanocomposite

Thin Films

P. Dubey1, Gabriel Lopez

1, Gustavo Martinez

1 and C.V. Ramana

1

1Mechanical Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA


We report on the structural and mechanical properties of ~60 nm thick W1-yMoyO3

nanocomposite films, which are of current interest as structural and electrode materials in energy

technologies. The W1-yMoyO3 thin films were sputter-deposited onto Si(100) by varying the

growth temperature (Ts) ranging from 25 ºC to 500 ºC. Molybdenum content in the films was

varied in the range of 0.00-0.36 atomic fraction (at.%) by employing the target with variable Mo

content in the W-Mo alloy composition. Structural and mechanical characterization of the W1-

yMoyO3 films was performed to understand the effect of Mo content and Ts on the mechanical

behavior. The results indicate that the effect of Ts is significant on the growth and microstructure

of W1-yMoyO3 films. The W1-yMoyO3 thin films were amorphous up to Ts=300 oC, at which point

amorphous-to-crystalline transformation occurs. W1-yMoyO3 nanocomposite films exhibit a

combined WO3 and MoO3 monoclinic phase structures; however, WO3 was predominant. The

peak intensities of MoO3 monoclinic phase increased with increasing Mo content in the films.

The nanoindentation results indicate a non-monotonic mechanical response (hardness (H) and

reduced elastic modulus (Er)) with increasing Ts. A significant change in H and Er values has

been observed Ts= 300 ºC. The W1-yMoyO with y = 0.05 at.% exhibited maximum hardness (~

21 GPa) and Er (216 GPa) values. A strain rate dependence of hardness value of W1-yMoyO films

has been observed.

August 4th, 2016

Abstracts

*Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA 22904

Contacts on WSe2: Interface Chemistry and Band Alignments

Christopher M. Smyth1, Rafik Addou1, Stephen McDonnell*, Jiyoung Kim,1 Christopher L. Hinkle1 and Robert M. Wallace1

Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, TX, 75080, USA


Two dimensional materials, specifically transition metal dichalcogenides (TMD), with atomic scale thickness, tunable bandgap (~1.1-2.2 eV) with composition and layer number, and mobilities in the same order as existing Si MOS channels, have emerged as strong candidates to complement or even supplant current Si-based device technology.1 WSe2 is of particular interest as the channel material in p-FETs due to its superior hole mobility previously reported as high as 500 cm2/V-1 s-

1.2 However, parasitic contact resistance continues to limit advances in TMD-based device performance.2

In this work, the interface chemistry formed between a low work function (WF) metal (Sc) and high WF metal (Pd) and WSe2, respectively, and its dependence upon the deposition chamber ambient is investigated. The interface chemistry was monitored in-situ using X-ray photoelectron spectroscopy (XPS). The number of layers consumed by reactions between metal and mono/few layer exfoliated WSe2 flakes is quantified using the 2LA(M) Raman mode wavenumber. The secondary electron cut off band was probed with XPS to monitor the WF in-situ following stepwise metal deposition and subsequent annealing under ultra-high vacuum (UHV).

Significant variation in reactivity between contact metal and WSe2 were observed. Notably, Pd forms a van der Waals interface (no alloying) with WSe2 under either UHV or high vacuum (HV) conditions, whereas Sc aggressively reacts with the substrate under both UHV and HV conditions. Following Sc deposition and in-situ Si capping, the spectral features indicative of monolayer WSe2 are no longer detectable, which indicates at least an entire WSe2 layer is consumed through interface reactions. In addition, the WF of Pd-WSe2 decreases from 4.8 eV (as-exfoliated WSe2) to 4.5 eV as Pd is deposited until a continuous film is achieved and the WF subsequently moves to that expected for Pd(111). In contrast, the WF trends lower towards that of bulk Sc (3.5 eV) as Sc is deposited, despite the formation of Sc(OH)x in-situ. These results provide insight into the chemistry and band alignment at the critical metal-WSe2 interface.

This work was supported in part by NSF Award No. 1407765, the Center for Low Energy Systems Technology (LEAST), one of six centers supported by the STARnet phase of the Focus Center Research Program (FCRP), a Semiconductor Research Corporation program sponsored by MARCO and DARPA, and by the Southwest Academy on Nanoelectronics (SWAN) sponsored by the Nanoelectronic Research Initiative and NIST.

[1] Schwietz, F. Proceedings of SPIE, 2014, 9467. DOI: 10.1117/12.2177033

[2] Liu, W.; Kang, J.; Sarkar, D.; Khatami, Y.; Jena, D.; Banerjee, K. Nano Lett. 2013, 13, 1983-1990.

The Graphene/Co3O4(111) Interface: Implications for other oxides and spintronics

O. Olanipekun1, S. Lightbourne1, B. Pollok1, M. Zhang1 , J. A. Kelber1, T. Cheng2, Y. Liu2,

and W.A Goddard III2

1Department of Chemistry, University of North Texas, 1508 W. Mulberry Street, Denton, TX, 76201

2Materials and process simulation center, California Institute of Technology, 1200 E. California

Boulevard, Pasadena, CA, 91125


Continued downscaling of CMOS technology is approaching practical and fundamental limits, hence the interest in spintronic devices, including those involving graphene. Inefficient injection of spin-polarized electrons into a non-polarized semiconductor channel, however, is a major drawback. A potential alternative is to induce spin polarization in graphene by interfacial spin interactions with a spin-polarized dielectric substrate or overlayer such as a magnetic oxide. Substrate-induced spin-polarization of electrons in 2D materials including graphene—or even simply graphite-- may serve as a better alternative to spin injection for spintronic devices as evidenced by recent experiments with graphene grown directly on Co3O4(111)/Co(0001)[1,2]. Experimental and theoretical studies indicate that graphene nucleates by C MBE on p-type Co3O4(111) with an interfacial graphene layer distorted by C-O interfacial bonding and significant carbon to oxygen charge transfer [3]. The results strongly suggest that similar results should be observed on other p-type oxides including various spinels with interesting magnetic properties. In contrast, n-type oxides should not exhibit graphene nucleation. Indeed, recent experiments show that C MBE on n-type Cr2O3(0001) below 800 K yields only disordered graphite with C desorption from the surface at > 800 K. Implications for graphene growth on other magnetic oxides will be discussed. Acknowledgement: Work at UNT was supported by the NSF (ECCS-1508991), by C-SPIN, a funded center of STARnet, a Semiconductor Research Corporation (SRC) program sponsored by MARCO and DARPA under task IDs 2381.001 and 2381.006. Research at Caltech was supported by the NSF (DMR-1436985) and DOE (DE-SC0014607) References: [1] M. Zhou, et al., J. Phys. Condens. Matter 24, 072201 (2012). [2] Y. Wang, et al., J. Phys. Condens. Matter 25, 472203 (2013). [3] J. A. Kelber, et al., Proc. IEEE Conference on Interconnect, Silicon, and Integrated

Circuit Technology (Hangzhou, China) Oct. 25-27, 2016 (accepted for publication)

Optical properties of graphene oxide and its biological and optoelectronics applications.

A. Naumov1, Md. T. Hasan1, M. Culp2, C. Pho1, B. Senger1

1Department of Physics and Astronomy, Texas Christian University, 2800 S University Dr, Fort Worth, TX 76129

2Department of Physics, St. Mary's University of Minnesota, 700 Terrace Heights, Winona, MN

55987


Optical applications of graphene are limited due to its electronic structure of a zero-gap semiconductor. Its derivative graphene oxide (GO) provides a new avenue to utilizing graphene in a number of applications as an optically-emissive material. In our work we controllably modify optical response of graphene oxide via oxidative processing. Timed oxidative treatment affects solubility, absorption and fluorescence spectra of graphene oxide introducing >100 nm spectral shifts. Both the intensity of the emission and the size of the optical band gap can be varied via controlled oxidation, providing a route to altering GO electronic structure. Thermal processing reverses the increase in fluorescence intensity with no apparent spectral shifts. Based on the oxidation-induced spectral changes we infer that graphene emission occurs due to defect-localized graphitic islands in the disordered sp3 GO platform. The aforementioned techniques allow tailoring electronic structure and thus optical properties of graphene oxide for a particular application including optoelectronics and biological imaging. In the latter modality graphene oxide shows multicolor emission on the single-flake microscopic level and exhibits cellular internalization into healthy HEK-293 and cancer HeLa cells. GO is non-toxic up to the doses of 15 g/mL, water-soluble and possesses a large platform for functionalization, which all together makes it a promising candidate for molecular imaging/drug transport.

Aromatic/Boron Carbide Composites: Emerging Materials for Neutron

Detection and More

A. Oyelade1*, B. Dong1, N. Nandagopal1, E. Echeverria2, P. A. Dowben2 and J.A. Kelber1*

1Department of Chemistry, University of North Texas, Denton, TX 76203, USA

2Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588

* Email: [email protected]

Semiconducting boron carbide films are of interest for neutron detections and other applications. A major drawback, however, is that they are poor semiconductors with high defect levels and low charge carrier mobilities. We have developed semiconducting composite films using plasma-enhanced chemical vapor co-deposition (PECVD) of pyridine (C5H5N) with orthocarborane (ortho-B10C2H12) to obtain tunable and repeatable pyridine/orthocarborane film stoichiometries. These novel composite films exhibit greatly enhanced charge generation in zero bias neutron voltaic experiments compared to films without pyridine [1]. Chemical and electronic structures of these materials were characterized by x-ray photoemission spectroscopy (XPS), ultraviolet spectroscopy (UPS) and variable angled spectroscopic ellipsometry (VASE) and by photoluminescence, and capacitance/voltage and current/voltage measurements [2]. The results show that pyridine bonding to carborane B sites yields pyridine-like states near the valence band maximum and carborane-like states near the conduction band minimum, as well as an indirect band gap (~1.7 eV) over a range of pyridine/orthocarborane stoichiometries. This energy is significantly narrower than that for boron carbide films without pyridine (3.0 eV), and lower than the exciton formation energy (~ 2.0 eV). This yields greatly enhanced exciton unbinding in films with pyridine [2]. Transport measurements also show that pyridine addition yields an order-of-magnitude increase in charge carrier lifetimes [2]. New results indicate an even narrower band gap (1.0 eV) for aniline-orthocarborane films. These results suggest enhanced potential for aromatic/boron carbide films not only for neutron detection but also for photocatalysis and photovoltaics. Acknowledgements: This work was supported by the US Defense Threat Reduction Agency under Grant. No: HDTRA1-14-1-0041 at UNT and UNL. References [1] E. Echeverria, et al., Appl. Phys. A 118 (2015) 113. [2] E. Echeverria, et al., J. Phys. D.: Appl. Phys. (in press)

A Study of the Controlled Nucleation and Grain Morphology of WSe2 Grown by Molecular Beam Epitaxy

R. Yue1, L. A. Walsh1, Y. Nie1, A. Barton1, H. Zhu1, Z. Che1, D. Barrera1, R. Addou1, L. Cheng1, N. Lu1, M. J. Kim1, J. Hsu1, J. Kim1, L. Colombo2, Y. Chabal1, R. M. Wallace1, K. Cho1, C. L. Hinkle1

1Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas

2 Texas Instruments, Dallas, Texas


Transition metal dichalcogenides (TMDs) are 2-dimensional, layered materials with composition and thickness dependent electronic properties. Due to the weak van der Waals interactions between adjacent layers, TMDs enable heterostructure growth with relaxed criterion for lattice matching, allowing the selection of materials based primarily on their electronic properties and quantum mechanical effects.[1] Among these materials, WSe2 is one of the most interesting TMDs due to its band alignment and carrier effective mass.[2] In this work, we demonstrate crystalline WSe2 growth by molecular beam epitaxy (MBE) and show how the van der Waals interactions allow for heteroepitaxy of significantly lattice-mismatched materials without strain or misfit dislocations. Yet, at the same time, the VDW interactions are strong enough to cause rotational alignment between the epi-layer and the substrate, which plays a key role in the formation of grain boundaries. To suppress nucleation and enhance larger area 2D growth, the complex interactions related to nucleation and growth was investigated. It is noted that W flux and substrate temperature primarily govern the competition between the attachment and diffusion rates and are critical to controlling the WSe2 nucleation and grain shape. The growth mode is primarily affected by the Se:W flux ratio which, in conjunction with lower nucleation rates, allows for larger 2D grain growth. These findings have resulted in a significant improvement in grain size, an order of magnitude larger than any MBE grown TMDs reported.

This work is supported in part by the Center for Low Energy Systems Technology (LEAST), one of six centers supported by the STARnet phase of the Focus Center Research Program (FCRP), a SRC program sponsored by MARCO and DARPA. It is also supported by the SWAN Center, a SRC center sponsored by the NRI and NIST, the Texas Higher Education Coordinating Board’s Norman Hackerman Advanced Research Program, and the NSF Award No. 1407765. References: [1] C. Gong et al, Applied Physics Letter 103, 053513 (2013) [2] A. M. Jones et al, Nature Nanotechnology 8, 634 (2013)

Direct Growth of h-BN(0001) on RuO2 by ALD and MBE

J. Jones*, B. Beauclair and J. A. Kelber

Department of Chemistry, University of North Texas, 1504 W. Mulbery St. Denton, TX 76201


Hexagonal BN(0001) is an important substrate for magnetic tunneling applications and for

graphene growth [1]. The ability to grow BN and graphene by direct methods without physical

transfer is a critical step in the industrial scale development of 2D electronic and spintronic

devices. We report the use of atomic layer deposition (ALD), using BCl3 and NH3 cycles at 600

K, to grow multilayer h-BN(0001) on a thin RuO2 film grown on Ru(0001). Although ALD has

been used to grow multilayer BN on transition metal surfaces [1,2], this is the first report of such

growth on an oxidized surface. X-ray photoelectron spectroscopy (XPS) data indicate the

growth of stoichiometric h-BN, with total film thickness linearly proportional to the number of

BCl3/NH3 cycles, up to a total thickness of 6 monolayers. XPS data also indicate that the thin

oxide substrate layer remains intact during the ALD growth process. Low energy electron

diffraction (LEED) data yield a complex pattern, but indicating that the BN later is in registry

with respect to the substrate lattice. The ability to grow high quality h-BN(0001) on oxide

substrates greatly increases the potential approaches for integrating BN and graphene/BN

heterostructures with other materials by industrially scalable methods.

Acknowledgements: This work was supported by C-SPIN, a funded center of STARnet, a

Semiconductor Research Corporation (SRC) program sponsored by MARCO and DARPA under

task IDs 2381.001 and 2381.006. BB also gratefully acknowledges a STARnet undergraduate

internship.

References

[1] M.S. Driver, J.D. Beatty, O. Olanipekun, K. Reid, A. Rath, P.M. Voyles, J.A. Kelber,

Langmuir 32 (2016) 2601.

[2] J.A. Kelber, in: Direct Graphene Growth on Dielectric Substrates, edited by J. E. Morris and

K. Ineiewski, CRC Press, Boca Raton, Fl, 2013, pp. 89-113.

Plasma Sterilization

S. Patel1, A. Gemsheim1, L. Overzet1, and M. Goeckner1

1Department of Electrical Engineering, The University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX, 75080

Email: [email protected] & [email protected]

The Food and Drug Administration (FDA) currently has approved a number of methods for the elimination of bacteria off of medical instruments.1 This includes (Alcohol, Formaldehyde, Glutaraldehyde, etc.), heat (Steam, Flash, etc.), and others (Hydrogen Peroxide Plasmas, etc.). We are working to better understand atmospheric dielectric barrier discharges (ADBD) because it has been shown that ADBD can sterilize bacteria quickly and effectively under circumstances. The goal of this work is to develop a fundamental understanding of how ADBD’s sterilize as to pair speed, safety, and efficacy. Prior researches have suggested that ADBD sterilization occurs because bacteria walls are bombarded with “reactive oxygen/nitrogen species” (so-called “RONS”). These reactive species are thought to sufficiently damage cell walls to lead to apoptosis. ADBDs can be used to form these reactive RONS in standard atmospheric pressure. The ADBD themselves are created by applying a large oscillating potential to metal contacts separated by a dielectric layer. The resulting micro-discharges dissociate surrounding air to create RONS. Our preliminary experiments show a reduction in bacteria colonies after being exposed to the ADBD effluent under certain conditions and little to no reduction in the numbers of colonies when exposed to the ADBD under other conditions. We have made some measurements of the RONS in the effluent as well as other parameters of the ADBDs as part of investigating this dependence. In this presentation, we will discuss our current results and their implications to the model of RONS induced sterilization. References: [1] “U.S. Food and Drug Administration,” Liquid Chemical Sterilization. [Online]. Available: http://www.fda.gov/medicaldevices/productsandmedicalprocedures/generalhospitaldevicesandsupplies/ucm208018.htm. [Accessed: 01-Apr-2016]. Acknowledgements: MBS Healthcare LLC. UTD OSP

Plasma Chemistry at the Air Force:

From the Fundamental to the Practical

Shaun Ard, Nicholas Shuman, Al Viggiano

Air Force Research Laboratory, Kirkland AFB

The plasma chemistry group at Air Force Research Laboratory has long been charged with the study of the kinetics of charged species (ion-neutral, electron-ion, ion-ion, etc.) primarily in relation to ionospheric applications. World unique instrumentation has been developed to study these reactions over a wide range of conditions (temperature, pressure, electron density). In recent years we have applied this instrumentation to a variety of new contexts, ranging from fundamental plasma interactions to real world plasma applications. The first part of the talk will focus on a recently developed experimental technique allowing for the study of several categories of chemical interactions previously inaccessible to experiment. One example of note is electron attachment to unstable radical species, such as CxFy. Of fundamental interest due to the difficult nature of dealing with such ephemeral species, these studies allow for extrapolation of this kinetic information to pressure, temperature, and non-thermal regimes of interest in industrial applications of fluorocarbon plasmas. The second part of the talk will focus on the Air Forces efforts towards artificial plasma enhancement in the ionosphere to mitigate the deleterious effects of scintillation on communications. The Air Force has previously pursued artificial plasma production, primarily in the form of releases of materials readily ionized by sunlight (i.e. Li, Ba, etc.). Current work focuses on expanding capabilities to remove the limitation of daytime use by use of chemi-ionization. A series of lanthanide metals, and some transition metals, have oxide bond strengths larger than the oxide ionization energy, such that La + O → LaO+ + e- is exothermic and potentially spontaneous. Laboratory work on these systems, as well as field experiments of their deployment will be discussed.

Covalent Nitrogen Doping of 2D Transition Metal Dichalcogenides by Remote N2 Plasma

A. Azcatl, X. Qin, C.Zhang, L. Cheng, Q. Wang, N. Lu, M. J. Kim, J. Kim, C. L. Hinkle,

and Robert M. Wallace

1Materials Science and Engineering Department, University of Texas at Dallas, 800 W.

Campbell Road, Richardson, TX 75080-3021


Two-dimensional (2D) transition metal dichalcogenides (TMD) are semiconductor materials that can potentially be employed as channel materials in tunnel field-effect transistors (TFETs) for beyond Si-based CMOS low power applications.[1] A key requirement for the realization of the proposed TFET structures is the controllable doping for the 2D TMDs materials. Molecular doping is a strategy that has been studied for doping of TMDs, however, due to the non-covalent bonding nature of the dopant molecules, this process has been limited by their volatility over time, making the control of the doping concentration a challenge. [2,3] Alternatively, it has been reported that when MoS2 is exposed to phosphorous-based plasma treatments, phosphorous dopants can be introduced in the MoS2 structure, resulting in p-type doping. [5] Yet, due to the weak van der Waals interlayer forces, layer etching can occur as a side effect from the plasma exposures.

Encouraged by the efforts on the exploration of plasma assisted doping strategies for

TMDs, here the use of remote N2 plasma exposure on MoS2 and WSe2 is proposed as a route for nitrogen doping of these materials. In this study, the surface chemistry of the TMDs upon sequential N2 plasma exposures was monitored in-situ by X-ray Photoelectron Spectroscopy. The chemical analysis from XPS indicates that nitrogen substitutes the chalcogen atom while, in parallel, interacts covalently with the transition metal. It was found that the nitrogen concentration in the TMDs can be controlled with N2 exposure time. Finally, Raman Spectroscopy and Photoluminescence Spectroscopy studies show that the presence of covalent nitrogen can induce compressive strain in these TMD materials. This study will provide insights for the understanding of the interaction of 2D TMDs with a non-metal dopant atom, which represent an important contribution for the realization of 2D electronic devices.

This work is supported in part the Center for Low Energy Systems Technology (LEAST), one of six centers supported by the

STARnet phase of the Focus Center Research Program (FCRP), a Semiconductor Research Corporation program sponsored by MARCO and DARPA, and by the SWAN Center, a SRC center sponsored by the Nanoelectronics Research Initiative and NIST.

References [1] Jena, D. Proc. IEEE, 101, 7, 1585–1602 (2013). [2] H. Fang, et al. Nano Lett. 12, 7 , 3788–3792 (2012). [3] D. Kiriya, et al. J. Am. Chem. Soc. 136, 22, 7853–7856 (2014). [4] A. Nipane, et al. ACS Nano, 10, 2, 2128–2137 (2016).

Excitons at interfaces in ellipsometric spectra

Stefan Zollner,1 Nuwanjula Samarasingha,1 Cesar Rodriguez,1 Jaime Moya,1 Nalin Fernando,1 Patrick Ponath,2 Kristy Kormondy,2 Alex Demkov,2 Dipayan Pal,3 Aakash Mathur,3 Ajaib Singh,3 Surjendu Dutta,3 Jaya Singhal3 and Sudeshna Chattopadhyay3

1Department of Physics, New Mexico State University, Las Cruces, NM 88007

2Department of Physics, University of Texas at Austin, Austin, TX 78705 3Department of Physics, Indian Institute of Technology, Indore, India


The presence of excitonic features in the optical constants and ellipsometry spectra of bulk semiconductors and insulators has been known for many years. In Si, Ge, and GaAs, the E1 critical points are strongly enhanced by two-dimensional “pancake” excitons, even at room temperature. Three-dimensional excitons have been seen in temperature-dependent ellipsometry spectra for GaP and Ge. More recently, it was shown that excitons also have an important influence on the dielectric function of bulk SrTiO3. An exciton is an electron-hole pair bound by the Coulomb interaction, with properties similar to a hydrogen atom. The influence of excitonic absorption on the complex dielectric function of bulk materials was described by Tanguy. In a thin epitaxial layer (with a thickness below the excitonic Bohr radius) on a substrate with a different band gap, the wave functions of the electron and hole are strongly modified. In a thin type-I quantum well, consisting of a narrow-gap semiconductor grown on a large-gap substrate, both the electron and the hole are confined, which leads to an increase in the dipole overlap matrix element. Therefore, the dominant absorption peak at 4.2 eV is larger in a 20 nm thick SrTiO3 layer on a LaAlO3 substrate than in bulk SrTiO3. (The band gap of LaAlO3 is larger than that of SrTiO3.) On the other hand, in a staggered type-II quantum well, either the electron is confined, or the hole, but not both. Therefore, the overlap dipole matrix element (and thus the excitonic absorption) is strongly reduced, because one quasiparticle resides in the quantum well and the other one in the substrate. If a SrTiO3 layer is grown on Si or Ge, the valence band maximum occurs in the substrate, while the conduction band offset is very small. Therefore, the exciton wave function is delocalized (deconfined), which reduces the dipole overlap matrix element. Therefore, the real and imaginary part of thin SrTiO3 layers on Si or Ge are much smaller than in the bulk and decrease monotonically with decreasing thickness. A similar effect can be seen for thin ZnO layers on Si as a function of thickness. The real and imaginary parts of the dielectric function of SrTiO3 are not only affected by layer thickness. For example, a very thick polycrystalline SrTiO3 layer on Si has a much lower dielectric function than a single-crystalline SrTiO3 substrate. Clearly, the overlap matrix element is the same for both single- and poly-crystalline materials. In this case, we speculate that the magnitude of the dielectric function is related to other Tanguy parameters, perhaps the excitonic binding energy or the exciton decay rate (broadening).

STRUCTURAL AND DIELECTRIC CHARACTERIZATION OF LEAD-FREE CALCIUM AND CERIUM BaTiO3 MODIFIED CERAMICS

Juan A. Duran 1*, Cristian Orozco 1 and C. V. Ramana1

1Department of Mechanical Engineering, University of Texas at El Paso,

El Paso, Texas 79968, USA

Email:[email protected]

Polycrystalline electro-ceramics such as Barium Titanate (BaTiO3) have opened a new era of exploration in the semiconductor industry. Interest in lead-free ferroelectric piezoelectrics has captured the attention of researchers over the years due to the on-going need to find a potential replacement of commercial piezoelectric-lead zirconate titanate (PZT) based sensors and actuators, which currently face global restrictions due to its high toxicity lead-content [1]. Barium Titanate ceramics are widely used in the manufacturing process of multilayer capacitors, thermistors, etc., due to its relatively high dielectric constant [1, 2]. It has been demonstrated that the co-doping approach is an efficient method of improved physical and electrical properties for this family of compounds, having the general formula ABO3. Structure, morphology, and regulation of the dielectric properties via close-composition intervals is demonstrated for variable-cerium, constant-calcium co-doped barium titanate (Ba0.80Ca0.20CeyTi1-yO3; x=0.0-0.25; referred to BCCT). The effect of variable Ce-content on the structure and dielectric properties of BCCT is investigated. X-ray diffraction spectra confirms the studied samples are mainly in BT tetragonal phase with a small secondary phase detected as CaTiO3 in BCCT for y = 0.20 and 0.25. However, the lattice parameter reduction was evident with increasing Ce-content. Composition-driven dielectric constant leap (4,000-5,500) was observed from intrinsic BCT to BCCT for (y = 0.0-0.04). The temperature-dependent dielectric constant showed a transition temperature, which decreased with progressive addition of Cerium content. The Curie point, Tc, diminishes from 120 to 50 °C for (y = 0.0-0.04) showing a decrease in the ferroelectric to paraelectric state. Hence, the solubility limit for cerium in BCT ceramics may have been reached. References: [1] Brajesh, K., Kalyani, A. K., & Ranjan, R. “Ferroelectric instabilities and enhanced piezoelectric response in Ce modified BaTiO3 lead-free ceramics”. Applied Physics Letters, 2015. [2] Heywang, Walter, Karl Lubitz, and Wolfram Wersing. “Piezoelectricity: evolution and future of a technology”, Vol. 114. Springer Science & Business Media, 2008.

august 3rd and 4 , 2016 university of texas at dallas...

Documents