fundamentals on surface analysis

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표면분석입문과정 2009

표면분석개론Fundamentals on Surface Analysis

김정원

나노구조측정센터한국표준과학연구원

(E-mail: [email protected])

May 8, 2019나노계측과학과

표면분석입문 2019, 김정원

Why are surfaces important?

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환경오염, 미세먼지?


Definition of Surface

▶ surface ↔ Interface

Outermost layers influencing top layer (2~10 layers)

0.5~ 3 nm (cf. underlying thin film – lubrication, optical properties)

▶ clean surface → interfaces : solid-vacuum (outer space )

solid - liquid

solid – solid

liquid – liquid

▶ Macroscopic surface phenomena

→ adsorption, bonding, catalysis, oxidation, corrosion and other surfacereactions, diffusion, desorption, melting and other phase transformation,

→ etching, crystal growth, nucleation, charge transport (atom, ion andelectron scattering) friction, lubrication, adhesion.

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History of Surface Science

G. Somorjai, Intro. to Surf. Chem. and Catal. (Wiley,1994)

Era of Industrial revolution1823, Pt-catalyzed reaction of H2 and O2

1835, Daguerre process (Ag-coated Cu)1850s, Tribology, Friction1874, Deacon process

1877, Gibbs: Thermodynamics1915, Langmuir adsorption

New era of microscopic investigation1950s, Gas phase molecular process

Petroleum refiningSolid-state electronic devices

1960s, New surface instrumentation & characterization techniques(molecular level studies)

4HCl + O2 → 2Cl2+ 2H2O400oC

CuCl2


Surface Concentration

G. Somorjai, Intro. to Surf. Chem. and Catal. (Wiley,1994)

Clusters, small particles, and thin films

Dispersion D =No. of surface atoms

Total no. of atoms

Large surface areaLow cost & efficient reaction medium

Link to current nanotechnolgy

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Contents

1. Kinematic theory of gases

2. 표면분석과 (초)고진공시스템

3. 간단한표면분석의원리및응용

4. 각분석법비교

5. KRISS 표면분석인프라소개

1 atm. = 1013 mbar = 1.013 bar = 760 mmHg = 760 Torr = 101,325 Pa (Nm-2)= 14.7 psi = 1.03 kg/cm2 SI unit


Why is UHV required for surface studies ?

1. To use of low energy electron and ion-based techniques

where : P - pressure [ N m-2 ] k - Boltzmann's constant ( = 1.38 x 10-23 J K-1 ) T - temperature [ K ]– collision cross section π(2r)2

eg) at 10-10 Torr, λ ~ 106 m, 1 atm, λ ~ 60 nm

Inelastic Mean Free Path (IMFP) : λk T

λ = [m]1.414 Pσ

λ = <v>/Z = 1/√2nσ n = N/V = P/kT (number density)

Collision frequency

2r

Average relative speed

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2. To enable atomically clean surfaces contamination-free state during the experiment.▶ Surface concentration:

bulk density : 1g/㎤ ( ice, water )

molecular density :

ρ = 6 ×10 23 × 1/18 = 3 × 1022 molecule/cm3

surface concentration :

σ = ρ2/3 = 1015 molecules/cm2

Why is UHV required for surface studies ?

Maintenance of a Clean Surface P < 10-9 torr

▶ Molecular flux: # of molecules per unit time & area

F = Nsurf/tA = P/√ (2πmkT)

= 1.33×10-4Pa/[2π(18g/6×1023)×1.38×10-23J/K)×298K]1/2

= 8.5×1014 molecules/cm2sec for H2O at RT, 10-6 Torr

≈ 1015


Degree of Vacuum

Pressure (torr)

Gas Density(molecules m-3 )

Mean Free Path (m)

Time / ML (s)

Atmospheric 760 2 x 1025 7 x 10-8 10-9

Low 1 3 x 1022 5 x 10-5 10-6

Medium 10-3 3 x 1019 5 x 10-2 10-3

High 10-6 3 x 1016 50 1

UltraHigh 10-10 3 x 1012 5 x 105 104

Collision Free Conditions P < 10-4 torr

Variation of Parameters with Pressure

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To achieve UHV (초고진공)

Typical procedure1. Proper pumping system: turbomolecular pump with rotary backing,

Ion pump with TSP (Titanium Sublimation Pump)

2. Leak check (ethanol spray or He leak detector)

3. Bake-out for ~20 hours at 150oC

4. Degassing all filaments


진공펌프 (저진공)

Rotary pump

Dry pump

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진공펌프 (고진공)

Diffusion pump Turbo pump

Ion pump Cryo pump


Things to be considered in UHV

1. Sealing (Cu Gasket or O-ring)

2. Pressure measurement (gauge)

3. Materials with low outgassing

4. Electrical connections (Ceramic seal tight)

5. Valves

6. Motion (Bellows, magnetic bar)

< Elastomer o-ring vs. Conflat flange(CF) sealing >< Ionization gauge >Baylard-Alpert, hot-cathode

~10-8 ~10-13

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Other pressure gauges

Cold cathode gauge upto 10-9 Torrfree from hot filament, no damage in air rush

Convectron or Pirani Gauge upto 10-3 TorrNonlinear, gas dependentSimilar to thermocouple gauge


RGA (residual gas analyzer)

- QMS (quadrupole mass spectrometer)

ionizerquadrupole

Faraday cup & multiplier

1. Pressure measurement 10-4 to <10-14 Torr2. Leak detector

After bake-outHydrogen becomes major

High mass signal: oil contamination

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Surface Analysis

PhotonIon

Electron

PhotonIon

Electron


InputSignal

output Signal

Electron

Ion

Ion Electron

Photon

Photon

AES, EELSLEED, SEMESD

EPMAEDS

INS

XPS, UPS

SIMS, ISS RBS, MEIS

LAMMAPSD, TPD

FTIR, TXRFSERS, XRD

PIXE

XPS : X-ray Photoelectron Spectroscopy

SIMS : Secondary Ion Mass Spectrometry

AES : Auger Electron Spectroscopy

PIXE : Particle induced x-ray emission (경주)

INS : Ion neutralization spectroscopy

Surface Analysis Tools

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표면분석국내현황

◈ 표면분석 기술 교류- 측정클럽 (http://metclub.kriss.re.kr) - 표준연 주관- 표면분석 공동분석 (RRT) - 산업 현장 측정 표준 확립- 표면분석 기술지원 - KBSI, KIST, NNFC, NCNT, DGIST 등

◈ 표면분석 교육- 한국표준과학연구원: 입문자 과정 - 매년 5월 (2일 과정)

전문가 과정 - 매년 9월 (3일 과정)

◈ 표면분석관련 학회 활동- 국내: 표면분석심포지움 (www.kossa2002.or.kr) - 매년 가을

14차 KOSSA: 2019년 9월 25~27일, 제천 청풍리조트- 국외: Practical Surface Analysis (PSA)

3년 주기 한일 공동개최PSA-19: 2019년 11월 4~18일, 일본 삿포로

표면분석교육

표면분석심포지엄

재료측정 국제 워크숍

표면분석 측정클럽

PSA-10


XPS (150 여대) AES (10 여대)SIMS (70 여대)

ATP (10 여대)

AXIS SUPRA (Kratos)

VersaProbe II (PHI)

ThetaProbe (Thermo Fisher Sci)

IMS-7f (Cameca)

NanoSIMS 50L (Cameca)

TOF.SIMS 5 (ION-TOF)

Scanning Auger Nanoprobe (PHI)

LEAP 4000 HR (Cameca)

국내표면분석장비현황

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전자/X-선과시료원자와의상호작용

X-선, UVElectron

표면탈출: XPS, UPS이차전자증폭발생: SEM

(EDX/WDX)

비탄성충돌: EELS

탄성충돌: XRD, LEED, RHEED

XES (X-ray emission)

(Auger electron)


Surface Sensitivity

The Inelastic Mean Free Path (IMFP) in metals is typically less than : 10 Angstroms ( 1 nm ) for electron energies in the range 15 < E/eV < 350 20 Angstroms ( 2 nm ) for electron energies in the range 100 < E/eV < 1400

i.e. the IMFP of low energy electrons corresponds to only a few atomic layers.

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P(d) = exp ( - d / )

Electron emission from a sample

IMFP

1.0 2.0 3.0 4.0


Film Thickness

Chemical StateElement Analysis Atomic Fraction

Elemental MappingDepth Distribution

1000 800 600 400 200 0

Fe 2p

Ni 2p

Binding Energy (eV)

Pure FeFe78-Ni72Fe51-Ni49Fe28-Ni72Pure Ni

108 106 104 102 100 98 96 940.0

5.0k

10.0k

15.0k

20.0k

25.0k

30.0k

Inte

nsi

ty (

cps)

Binding Energy (eV)

0 sec 3 sec 6 sec 9 sec 12 sec 15 sec 20 sec 30 sec 40 sec 50 sec 60 sec 70 sec 80 sec

XPS의응용

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AES

backscattered electron (BSE)

Auger electron secondary electron (SE)

radiative recombination

specimen surface

generation of electron-hole pairs

charge-carrier collection

bremsstrahlung X-rays

inelastically scattered electron

incident electron beam

excitation volume

unscattered electrons

elastically scattered electrons

characteristic X-rays

SEM Image

CL

EBIC

EELS, EFTEM

EDX, WDX

TEM image (DF)

SEM image

+-

EBSD

Diffraction

TEM image (BF) Diffraction

전자빔을이용한표면분석기술


Scanning Electron Microscopy Tunneling Electron Microscopy

전자현미경

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표면형상 (SEM) 결정구조 (TEM) 조성분포 (SEM, TEM/EDX)

CdTe Film Surface

CdTe Cross Section

CTEM 형상 (BF/DF image)

HR-TEM image 0 100 200 300 400

100

200

300

400

500

600Ge-KSi-K

Inte

nsi

ty

Depth (nm)

Si/Ge 다층박막 단면 분석

CIGS 박막 단면 분석

전자현미경의응용예


EKLL = EK - ELII – ELIII 입사전자에너지와 무관

Auger Electron Spectroscopy (AES)

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100 nm

0

10

20304050

60708090

100

0 50 100 150 200 250 300Sputter Time (min)

Ato

mic

Co

nce

ntr

atio

n (

%)

O

Al in oxide

Al metal Si

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4-1

0

1

2

3

4

5

x 10

4

Distance (µm)

(P-B

) cn

ts

Al2

Si2

깊이 분포 분석 공간 분포 분석정량 분석

0 200 400 600 800 1000 12002.0M

2.2M

2.4M

2.6M

2.8M

3.0M

3.2M

3.4M

3.6M

3.8M

4.0M

Fe

Fe77.7

Ni22.3

Fe50.6

Ni49.4

Fe27.6

Ni72.4

Ni

10kV 10nA-etch

Inte

nsi

ty (

arb

.un

it)

Kinetic energy (eV)

0 200 400 600 800 1000 1200

Ni

Fe77.7

Ni22.3

Fe50.6

Ni49.4

Fe27.6

Ni72.4

Fe

Inte

nsi

ty (

arb

.un

it)

Kinetic Energy (eV)0 100 200 300 400

0

20

40

60

80

100

16%

84%

Si Ge

Co

mp

osi

tio

n (

%)

Sputtering Depth (nm)

AES의응용예


이온에너지에따른물질과의상호작용과그의응용

~ eV

~ keV

~100 keV

~ MeV

Ion Beam Deposition

Sputtering (SIMS)Ion Beam Analysis(LEIS)

Ion ImplantationIon Beam Analysis(MEIS)

Ion Beam Analysis(RBS)

DamagedRegion

상온 ~ 26 meV

He Ion Micriscopy (HIM)

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Surface Spectrometry Surface Imaging Depth Profiling

0 1 0 2 0 3 0 4 0 5 0 6 0 7 01 0 0

1 0 1

1 0 2

1 0 3

1 0 4

1 0 5

1 0 6

B

S i

SIM

S In

ten

sity

(cp

s)

S pu tter D epth (nm )

깊이분포도원소 공간 분포원소분석 정량 분석

SIMS의응용예

0 200 400 600 800 1000100

101

102

103

104

105

106

107

10B+

11B+

29Si2

+

28Si2

+

Inte

nsi

ty

Sputter Time (s)


Evans Analytical Group

Defect analysis in Flat panel display by TOF-SIMS

Polydimethylsiloxane (PDMS) contamination in the stain

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결정성 분석조성 및 깊이분포 분석성분 원소 분석

RBS의응용예


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Technique Comparison


INS – Inelastic neutron scattering. Bombard a surface with neutrons – energy loss occurs due to the excitation of vibrations. It is most efficient in bonds containing hydrogen.LEED – Low energy electron diffraction. A beam of low energy (tens of eV) electrons bombard asurface; the electrons are diffracted by the surface structure enabling the structure to be deduced.RHEED – Reflection high energy electron diffraction. A high energy beam (keV) of electrons isdirected at a surface at glancing incidence. The angles of electron scattering can be related to thesurface atomic structure.EXAFS – Extended X-ray absorption fine structure. The fine structure of the absorption spectrumresulting from X-ray irradiation of the sample is analysed to obtain information on local chemicaland electronic structure.

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Radiation effects – Surface damage

Damage (penetration depth or momentum transfer, m∆v)photons < electrons < ions

Total damage ~ flux, energy / unit area


표면분석표준화연구-표면분석용인증표준물질(CRM) 개발

-공동분석을통한표면분석법표준화-국제표준화연구 : ISO-TC 201(Surface Chemical Analysis)

CCQM-SAWG (BIPM - Consultative Committee for Amount ofSubstance)

새로운표면분석법개발-초박막두께측정법 (SiO2, HfO2)

-중에너지이온산란법 (MEIS) : 원자층수준의깊이분해능 (MEIS imaging)-유기바이오표면분석법 (DESI, bio TOF-SIMS)-시분해광전자분광법 (TR-PES, PEEM)

표면분석법의응용연구- CIGS film조성의깊이분포도정량분석- In-situ XPS, UPS분석에의한박막증착기구연구- Bio-SIMS와광전자분광법이용유기물박막및생체조직분석- GCIB를이용한 depth profile방법표준화

Activities at KRISS

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◈ Traceability - CCQM SAWG - traceable to SI unit : m, mol

- by measurement equivalency of NMIs achieved by MRA of NMIs via Key Comparison

◈ International Standard - ISO/TC-201- approved measurement procedure

- practical application of analytical methods

◈ Certified Reference Material (CRM) - NMI- dissemination of traceability- certification by traceable methods

표면분석표준화요소


BIPM

national body for

standardization - MRA

CGPM

CIPM

CCBIPM

NMIs (NPL, NIST etc)

CIPM

define SI units

establish traceability

10 Consultative Committees

CCL 1952

CCM 1980

CCTF 1956

CCT 1937

CCPR 1933

CCEM 1927

CCQM 1993

CCRI 1958

CCAUV 1998

CCU 1964

CCQM

CMC claim

pilot study, key comparison

KCWG (Key Comparison)

GAWG (Gas Anal.)

EAWG (Electro. Anal.

IAWG (Inorganic Anal.)

OAWG (Organic Anal.)

BAWG (Bio Anal.)

SAWG (Surface Anal.)

7 Working Groups

국제도량형물질량자문위원회

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분과 분과명 국내전문가 ISO 표준 제정 현황제정완료 제정 중

SC1 Terminology 5

SC2 General Procedure 7 4

SC3 Data Management and Treatment 4 1

SC4 Depth Profiling 김경중 6 1

SC5 없어지고 SC7으로 합쳐짐

SC6 Secondary Ion Mass Spectrometry 김경중, 이태걸 9 2

SC7 Electron Spectroscopy 김정원, 김안순 25 3

SC8 Glow Discharge Spectroscopy - 5 1

SC9 Scanning Probe Microscopy 신채호 6 3

SC10 X-Ray Reflectivity 김창수 4+ 3

합계 74+ 18

ISO/TC-201 (from 1991) Surface Chemical Analysis


Thin film CRMs

Multilayer Thin Film : 5 items

Binary Alloy Thin Film : 3 items

Uniformly Doped Si Thin Film : 2 items

http://eshop.kriss.re.kr/

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시험분석목록

http://eshop.kriss.re.kr/

1. 나노소재평가/표면분석: 스타일러스단차측정, 표면분석시험, SIMS

나노소재평가/표면분석: SEM

2. 나노측정: SPM 측정

3. 신기능재료/표면분석: UPS 측정

4. 첨단측정장비: TEM


SIMS (CAMECA IMS-7f )

TOF-SIMS IV (ION-TOF)

TEM (FEI, Technai F30)

Facilities at KRISS

XPS (VersaProbe II)

분석이슈가있는의뢰환영 !!

AESAPT

fundamentals on surface analysis

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