ToF-SIMS - semat

Surface Analysis by XPS & ToF-SIMS Basics, Strengths, and Limitations Michael Bruns

Institute for Applied Materials (IAM-ESS)

KIT – University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association

[email protected]

www.kit.edu

The Merger of Forschungszentrum Karlsruhe and Universität Karlsruhe

1956 Karlsruhe Nuclear Research Center

10/ 2009 KIT Campus North

2

Michael Bruns 18º Workshop SEMAT/UM, Nov. 11th, 2013

Institute for Applied Materials (IAM-ESS) Surface Analysis Group

Thermo Fisher Scientific: K-Alpha & Glovebox ESCA5/Alpha110

XPS • Quant. Chemical Information • Depth Profiles

Surface Analysis FE-SEM

• Chemical & Molecular Information • 3D Elemental Information

Topography

EDS Elemental Images

Zeiss GmbH: Merlin

6


ToF-SIMS

inert transfer

ION-TOF GmbH: TOF.SIMS 5


Textbooks X-ray Photoelectron Spectroscopy Auger Electron Spectroscopy Time-of-Flight Secondary Ion Mass Spectrometry

~ 60

~ 200 €

XPS AES ToF-SIMS

~ 200 €

 www.xpssimplified.com 7



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Surface Analysis Thin Film Analysis

Surface Analysis

Top Surface Near Surface



Thin Film

Thin Film

Coating

Coating

Bulk Analysis 3 nm 10 nm 10-100 nm 100-1000 nm

Bulk

9



Surface Analysis Analytical Resolution Versus Detection Limit

10



X-Ray Photoelectron Spectroscopy (XPS) Relationship to Electronic Structure

Au

EB = hν - EK - ω

(mono) Al Kα 1486.6 eV Mg Kα 1253.6 eV

s p d f

singlet doublet (3/2 & 1/2) doublet (5/2 & 3/2) doublet (7/2 & 5/2)

John F. Watts, John Wolstenholme, An Introduction to Surface Analysis by XPS and AES, Wiley & Sons, Chichester, UK, 2003 11



XPS Characteristics 

Depth of analysis 5nm



All elements except hydrogen



Readily quantified



All materials (ultra high vacuum compatible)



Depth profiling by angle resolved XPS or sputtering



Analysis area mm2 to 30 micrometres



Chemical images Theta Probe Complementary Methods

 ToF-SIMS  LEIS  RBS  FE-SEM &EDS  TEM VG ESCA5 & Thermo Fisher Alpha 110 Analyzer 12


Thermo Fisher K-Alpha

Application Lab, UK Institute for Applied Materials (IAM-ESS) Surface Analysis Group

XPS Instrumentation: X-Rays

Mg

13



XPS Instrumentation: Concentric Hemispherical Analyzer

-

+

Channeltron

Mu-Metal: Ni 81/Fe19 - Alloy 14



Speziation / Chemical Shift

15



Speziation – Chemical Shift

16



XPS: Depth of Analysis

λ ∝ ~ E 0 .5

Intensity as a function of depth 65% of the signal from

17


< 1λ

85% from

< 2λ

95% from

< 3λ


X-Ray Induced Auger Emission

EKL2,3L2,3(Z) = EK(Z) – [EL2,3(Z) + EL2,3(Z + 1)]

18



MgKα vs. AlKα X-Rays 1253.6 eV

1486.6 eV

• XPS and Auger peaks

19



Electron Spectroscopy (AES) Electron Solid Interactions Primary Electron Beam Auger-Electrons

Secondary Electrons • All elements Z>2

Backscattered Electrons

X-rays Surface

• Conducting and semiconducting surfaces • Spatial resolution 0.1at.% • Quantitative elemental information

3µm Exitation Volume 20



MgKα vs. AlKα X-Rays 1253.6 eV

1486.6 eV

• XPS and Auger peaks • Shake-up/off satellites • X-ray satellites • Background • Surface charging

22



Shirley Type Background

b

∫ Ix (Ex )∗ dEx

I*b (Eb ) = Ib − Ia 0 a

∫ Ix (Ex )∗ dEx

0

23



Monochromatic AlKα X-Rays FWHM 0.85  0.26 eV 180° spherical sector analyser

photoelectrons focused by high-transmission lens

multi-channel detector

toroidal crystal

anode electron gun

24


Bragg: nλ = 2d sinθ θ = 78.5°, AlKα  Quartz 1010 Institute for Applied Materials (IAM-ESS) Surface Analysis Group

Speciation: SAMs for Biological Applications X-Ray Induced Damage H3C

O

O

O

O

S

 microfocused X-rays

Au

C 1s 1. Multi-point analysis with short acquisition time 2. Collapse data set to one single spectrum

C-H

intensity [arbitrary units]

C-O

290

289

288

287

286

285

284

283

282

281

binding energy [eV]

SAM alteration dependant on the X-ray exposure time (-- as received, -- 9 min., -- 21min., -- 27 min.).

25



Thiol-SAMs

H N N H2N

Benzylguanine disulfide (BGT)

N O

O

O

S S

N

6

NH O

CH3

EG3OMe thiol HS

O

O 3

CH3

Methoxy-capped tri(ethylene glycol) undecanthiol

1. S. Engin, V. Trouillet, C. M. Franz, A. Welle, M. Bruns, and D. Wedlich, Langmuir 26 (2010) 6097-6101. 2. M. Bruns, C. Barth, P. Brüner, S. Engin, T. Grehl, C. Howell, P. Koelsch, P. Mack, P. Nagel, V. Trouillet, D. Wedlich, R. G. White, Surf. Interface Anal. 44 (2012) 909–913. 26



SNAP-tag system for covalent immobilization of proteins

Protein of interest SNAP

S

Applications

NH

N

N

 cell culture: cell adhesion, migration, differentiation

O

O CH3 3

 biosensors in diagnosis,

O

 lab-on-chip technology,

O

 …..

N

H2N

O 6

CH3

Au S

NH O

O CH3 3

O

O CH3 3

Au S

O

Au S

SNAP-tag system: genetically modified O6-alkylguanin-DNA alkyltransferase 27


Au S Au S Institute for Applied Materials (IAM-ESS) Surface Analysis Group

Thiol – SAMs for Biological Applications H N N H2N

Au-S-C -C-O-C-NH--N= CHO 1s C 1s 2p NS1s

N

N

-C-O-C-

O

pure BGT

BGT

S

O 6

NH O

Au

CH3

EG3OMe S

O

Au

O 3

intensity [arbitrary [arbitrary units] intensity units]

O

S

O-C=O O-C=O

EG3OMe

-C=O

CH3

168 292 536 404

166 160 290 286 162 282 534 288164 402 400 532 398284 530 396

158 280 528 394

binding energy [eV]

28



XPS Information Depth … Depends on Electron Emission Angle

29



Parallel ARXPS: non-Destructive Depth Profile

30



Parallel ARXPS: EG3OMe SAM non-Destructive Depth Profile H3C

atomic concentration [%]

120

O

O

O

O

S

Au

100 80

-C2H4O60

C 1s

-CH2-S-

40

Au O 1s 20 0 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 depth [nm]

31



High-sensitive Low Energy Ion Scattering SAM Thickness CH3 O O

Projectile: 3 keV 3He+

O O

27°

Au peak onset energy shift:  EG3OMe

= 200 eV  2.2 nm SAM thickness  well-ordered SAM

S

Au

Au

Reliable estimation of the SAM thickness is prerequisite for the reconstruction of non-destructive elemental depth profiles from parallel ARXPS data. 32


Qtac 100 Institute for Applied Materials (IAM-ESS) Surface Analysis Group

ER PES: EG3OMe SAM non-Destructive Depth Information CH3 O O

330 eV

1100 eV O O

-C2H4O-CH2-SAu

S Au 33



Sputtering Ion Solid Interaction

Implantation 34



Depth Information via Sputter Depth Profiles Analyzer

X-rays

35


Ar+ ion source


XPS Sputter Depth Profiles

DP Point BST right 2

5 0 0 .0 µm

Collaboration: Tascon GmbH, Heisenbergstr. 15, D-48149 Münster, Germany 36



XPS Sputter Depth Profiles Time-to-Depth Conversion

jP ⋅ Yi ⋅ M i ⋅ t z (t ) = N A ⋅ e0 ⋅ ρ i

37


jP

= Ion beam density

NA

= Avogadro constant

e0

= Elementary charge

t

= Sputter time

Yi

= Sputter yield

M

= Molecular weight

ρi

= Density


XPS Sputter Depth Profiles Loss of Chemical Information Ti4+

TiO2 intensity [arbitrary units]

Ti 2p Level 0 Level 1 Level 2 Level 3 Level 4

• 1 keV Ar+ ions • 20 s / level

475

470

465

460

455

450

binding energy [eV]

38



ToF-SIMS Time-of-Flight SIMS Principle

 A short-pulsed ion beam defines the starting point of the time-of-flight measurement.  All secondary ions are accelerated to the same kinetic energy: the time-of-flight for a given drift path varies as the square root of mass.  Time focusing devices (i.e. electrostatic fields) for good mass resolution.

39



ToF-SIMS Ion Solid Interaction Excitation Bombardment with primary ions, energy: 5-25 keV (Ga+, Aun+, Bin+, O2+, Cs+, Ar+, Xe+, ...)  Collision cascade in solid

Results Desorption of neutrals (95%), electrons, and secondary ions (+/-).  area 5-10 nm diameter  depth of origin 1-2 monolayers  Implantation of primary ions  Atoms relocation (mixing)  Damaging of organic molecules 40



ToF-SIMS Characteristics + + + + + + + + + +

detection of all elements isotope sensitivity chemical information low detection limit small information depth high depth resolution high lateral resolution high mass resolution high mass range parallel mass detection

-

quantification limited (requires standards) destructive

-/+

41


molecules, clusters ppm - ppb first 1-3 monolayers 3000 min acquisition time)

O 1s

Sn SnO

O1s Snap2

Si

SiO2

O1s Snap

500x500 µm2

! Different positions ! 47


XPS chemical images are very time consuming  Parallel imaging using Thermo Scientific ESCALAB 250 Xi Institute for Applied Materials (IAM-ESS) Surface Analysis Group

ToFSIMS Modes of Operation Surface Spectroscopy

Surface Imaging Analysis of the in-depth distribution of elements and molecules Depth Profiling

3D Analysis

48


Features:  elemental and cluster information  depth resolution < 1 nm  thin layers from 1 nm to > 10 µm


ToFSIMS Sputter Depth Profiling Dual Beam Mode

49



ToF-SIMS Sputter Depth Profile of a R.F. Magnetron Sputtered Li-Mn-O Thin Film calibrated by XPS

ECASIA 2013, Cagliari, Italy 50



Thank you! Florian Stemme

51

Vanessa Trouillet


Volker Vanessa Udo Winkler Oberst Geckle


ToF-SIMS - semat

ToF-SIMS - semat

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