X-ray Photoelectron Spectroscopy (XPS)€¦ · Cu Lα 929.7 3.8 Mg Kα 1253.6 0.7 Al Kα 1486.6 0.85 Si Kα 1739.5 1.0 Y Lα 1922.6 1.5 Zr Lα 2042.4 1.7 Ti Kα 4510.0 2.0 Cr Kα

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ISO 9001:2015

X-ray Photoelectron Spectroscopy (XPS)

Dr. Mark C. Biesinger

Director,Surface Science Western, University of Western Ontario




Instrumentation• Optical Microscopy • Scanning Electron Microscopy (SEM) • Field Emission Scanning Electron Microscopy (FESEM)• Energy Dispersive X-ray Spectroscopy (EDX)• Dynamic Secondary Ion Mass Spectrometry (SIMS)• Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS)• X-ray Photoelectron Spectroscopy (XPS)• Scanning Auger Microscopy/Auger Electron Spectroscopy

(SAM/AES)• Laser Raman Spectroscopy• Fourier Transform Infrared Spectroscopy (FTIR)• Surface Profilometry• Contact Angle Goniometer• Micro-Computed Tomography (Micro-CT)• X-ray Diffraction• Atomic Force Microscopy (AFM)• Microindentation Hardness Testing• Metallographic Preparation and Cross-Sectioning Facilities• Specialized Surface Preparation and Weathering Chambers• Corrosion and Electrochemical Testing Facilities


X-Ray Photoelectron Spectroscopy (XPS) – The Highlights

• Elemental and chemical state analysis of the outer surface of a solid samples

• Effective probing depth 5-10 nm• Varies slightly with sample composition• Can be varied with electron take-off (or sample) angle

• Detects elements from lithium to uranium • Quantitative• 0.01 to 0.5 atomic % detection limits

• Examples of chemical information that can be obtained• Metal oxides, hydroxides, carbides• Silicone, silica, silicon nitride or elemental silicon,• Fluorocarbon or fluoride, • Chromium 0, III or VI


Kratos AXIS Supra, Nova & Ultra


Photoelectric effect

Einstein, Nobel Prize 1921

Photoemission as an analytical tool

Kai Siegbahn, Nobel Prize 1981

The Photoelectric Effect


X-Ray Photoelectron Spectroscopy (XPS)

• Use X-rays to probe the surface of a sample• Photoelectrons are produced (photoelectric effect) and

can escape without energy loss from the outer few nanometres of the surface (substrate dependent)

microscopecrystal

electronbeamelectron gun sample

photoelectrons

electron energy analyzer


Photoelectron EjectionExample: Ni Metal 2p3/2

K 1s2 8333 eV

L3 2p3/24 852.5 eV

L1 2s2 1008 eV

M1 3s2 111 eV

L2 2p1/22 869.8 eV

M23 3p6 67 eVM45 3d8 ~3.2-3.3 eVN1 4s2 Conduction

Al(Kα) = 1486.7eV

B.E. = hv - K.E. - ɸs

The Einstein Equation

Electron K.E. = 634.2 eV


Spectroscopic Nomenclature

2p 3/2

Principal Quantum Number (n) or shell

Orbital angular Momentum number (l =0, 1, 2, 3 gives s, p d, f )

Total angular momentum(j = l+s)

1s

2s

2p

n=1, l =0, j=1/2n=2, l =0, j=1/2

n=2, l =1, j=3/2n=2, l =1, j=1/2

Degeneracy = 2j+1


X-rays

• X-rays are generated by high energy electron bombardment of a target species

• Target species must emit X-rays that have a narrow line width since this affects the energy resolution of the photoelectron peaks

• Energy of emitted X-rays must be high enough to excite photo-electrons lines for elements of interest

Line Energy (eV) Width (eV)Y Mζ 132.3 0.47Zr Mζ 151.4 0.77Nb Mζ 171.4 1.21Mo Mζ 192.3 1.53Ti Lα 395.3 3.0Cr Lα 572.8 3.0Ni Lα 851.5 2.5Cu Lα 929.7 3.8Mg Kα 1253.6 0.7Al Kα 1486.6 0.85Si Kα 1739.5 1.0Y Lα 1922.6 1.5Zr Lα 2042.4 1.7Ti Kα 4510.0 2.0Cr Kα 5417.0 2.1Cu Kα 8048.0 2.6

Ag(Lα) = 2984.2eV


X-ray Sources• Al(Monochromatic Kα) is standard for high

resolution work• Mg(Kα) gives a high X-ray flux, remove Auger

line interferences • Zr(Lα), Ag(Lα), Mo(Lα), Au(Mα), – higher energy

sources provide deeper analysis depths and can excite higher energy core levels

• He(I) and He(II) – valence band studies (UPS –Ultraviolet Photoelectron Spectroscopy)

• Synchrotron – high intensity, tunable, can get optimum surface sensitivity using a photon energy of approximately 40–50 eV above the peak of interest


IMFP – Inelastic Mean Free Path• IMFP is the depth that 1 sigma (68%) of

photoelectrons can escape from the surface without energy loss

• 99.7 % (3 sigma) of all photoelectrons come from 3 IMFP of depth


IMFP – Inelastic Mean Free Path• Example: Au substrate, Au 4f

photoelectrons BE ~ 84 eV • Al(Kα) =1486.7 eV, Au 4f KE =

1402.7 eV, IMFP = 1.78nm• Mg(Kα) =1253.6 eV, Au 4f KE =

1169.6 eV, IMFP = 1.45nm• Zr(Lα) = 2042.4 eV, Au 4f KE =

1958.4 eV, IMFP = 2.30nm• Synchrotron tunable source set to

200 eV, Au 4f KE = 116eV, IMFP = 0.466nm

• Au Substrate, C 1s ~ 285 eV, Al(Kα), KE = 1201.7 eV, IMFP = 1.582 nm

• C substrate, C 1s ~ 285 eV Al(Kα), KE = 1201.7 eV, IMFP= 3.113 nm


e-

hv

α

3λ dd

hv

α

3λ

e-

Angle Resolved Analysis

• Maximum sampling depth is at an electron take-off angle of 90 degrees (angle from surface to spectrometer)

• As take-off angle decreases sampling depth decreases• At 30 degrees take-off ~ 50 % of the depth at 90 degrees• At 15 degrees take-off ~ 25 % of the depth at 90 degrees


Survey Scan

• Contaminated Polyurethane SurfaceBinding Energy (eV)

02004006008001000

CPS

F 1s

F K

LL

O K

LL

O 1

s

N 1

s

C 1

s

Si 2

s

Si 2

p

24.2 at.%15.2 at.%3.4 at. %56.8 at.%

0.5 at.%

Fluorine Oxygen Nitrogen CarbonSilicon

CA = (IA/SA)∑ (In/Sn)


SURFACE SCIENCE W ESTERN

Unknown Sample, Al(K alpha) Source

C 1s

O K

LL

O 1s

O

x 104

2

4

6

8

10

12

CS

1000 800 600 400 200 0Binding Energy (eV)

Identifying Unknown Peaks

150

eV10

0 eV

200

eV

268

eV


10 Zn3d 33 U6p3 58 Os5p1 93 Ba4d3 *154 Si2s *230 Ta4d510 Cs5p *34 Nb4p 58 Nb4s 94 Fe3s *154 Dy4d 232 As A11 Cd4d *34 Sb4d *58 Se3d 95 Th5d3 154 Sb4s *232 Mo3d512 Si3a 34 W4f5 59 Ag4p 96 Ag4s *158 Bi4f7 234 Se3s13 Rb4p 35 W5p3 *60 Ir4f7 96 Ir5s 158 Cs4p3 235 Mo3d3

*13 Tl5d5 35 Re5p3 60 Er5s *96 U5d3 *159 Y3d5 *237 Rb3p315 Ba5p 36 Gd5s 60 Th6s *99 Hg4f7 160 Ga3s 237 Pr4p115 P3s 36 La5s *60 Xe4d5 100 Tl5p1 160 Bi5s *241 Ar2p315 Ne2p 37 Ta5p3 62 Xe4d3 101 Sb4p 161 Y3d3 242 Ta4d315 S3s *37 Ti3p 62 Ti3s 102 Pt5s *161 Ho4d 243 Ar2p115 Xe5s 37 Ce5s *63 Na2s 103 Hg4f5 163 Bi4f5 *244 W4d516 Tl5d3 38 Pr5s 63 Ir5p1 *103 Si2p3 *163 S2p3 246 Rb3p116 K3p 38 Hf5p1 63 Co3p 104 Si2p1 164 S2p1 247 Nd4p116 Cl3s 39 Sr4s 63 Dy5s 104 Pb5p1 *164 Se3p2 *250 Sm4p3

*17 Hf4f7 40 Ba5s 63 Ir4f5 *104 La4d *168 Er4d5 253 Ba4s18 La5p *40 Mo4p 65 Hf5s 105 U5d3 169 Cs4p1 257 W4d3

*18 Pb5d5 40 Tb5s 66 Pt5p1 *106 Ga3p3 170 Se3p1 *257 Eu4p318 Hf4f5 40 Sm5s 67 Mo4s 108 Au5s 173 Te4s *257 Br3s19 In4d 41 Nd5s 68 Cd4p *108 Ce4d 177 Er4d3 *260 Re4d519 Ce5p *42 Ne2s *68 Ni3p 109 Cd4s 180 Ba4p3 260 U5p120 Pb5d3 *42 V3p *69 Br3d5 *110 Rb3d5 *180 Tm4d 261 Se A20 Ho5p *43 Ru4p 70 V3s 110 Ga3p1 *182 Zr3d5 268 Sm4p120 Ga3d 43 U6p1 70 Br3d3 *111 Be1s *182 Br3p3 *268 As A21 Gd5p 43 Th6p3 71 U6s 111 Rb3d3 182 Th5p3 *269 Cl2s21 Sr4p 44 Cr3p 71 Ta5s 113 Ni3s 184 Zr3d3 *270 Sr3p321 Ca5s 44 Ca3s *71 Pt4f7 113 Te4p 184 Ge3s *271 Gd4p321 Kr4s *44 Te4d 72 Au5p1 *114 Pr4d 185 I4s *273 Os4d522 Sm5p 45 Ta5p1 74 Pt4f5 117 Bi5p1 *185 Se A 274 Re4d322 Eu5p *45 Re4f7 75 Ru4s *118 Tl4f7 *186 Yb4d5 274 La4s22 Ar3s 45 W5p1 75 W5s 120 Hg5s 189 Br3p1 *279 Ru3d5

*23 O2s *46 As3d *75 Cs4d5 *120 Al2s *192 B1s 280 Sr3p123 Pr5p 46 Os5p3 *75 Cu3p3 122 Cu3s *192 P2s 284 Eu4p123 Yb5p 46 Re5p1 *75 Al2p *122 Nd4d 192 Ba4p1 284 Ru3d325 Ca3p 47 Y4s 76 Tl5p3 122 Tl4f5 195 La4p3 *285 C1s25 Sn4d 47 Re4f3 76 Cr3s 123 I4p 195 U5p3 *286 Tb4p3

*25 Ta4f7 *48 Rh4p 77 Cu3p1 124 In4s *195 lu4d5 *287 Kr3s*25 Bi5ds *49 I4d5 77 Cs4d3 125 Ge3p3 *198 Cl2p3 288 Ce4s25 Nd5p 49 Th6p1 79 In4d 129 Ge3p1 199 Cl2p1 289 Gd4p126 Tb5p *50 Mn3p 81 Rh4s *133 Sm4d 201 Yb4d3 290 Os4d326 Dy5p 50 I4d3 81 Hg5p1 *134 Eu4d 205 Lu4d3 290 Th4s27 Y4p *50 Os4f7 83 Re5s *134 Ptp3 *205 Nb3d5 291 Se A27 Ta4f3 51 Ir5p3 *84 Au4f7 *134 Sr3d5 *206 Ce4p3 *292 K2p327 Bi5d3 51 Pt5p3 84 Os5s 135 Sr3d3 206 Xe4s *293 Dy4p328 Lu5p 51 Ho5s 85 Pb5p3 135 Ptp1 208 As3s 295 K2p129 Er5p 51 Mg2p 85 Mn3s 137 Tl5s 208 Nb3d3 *295 Ir4d529 Pb4s 52 Os4f5 86 Pd4s *137 Pb4f7 *209 Kr3p3 *302 Y3p3

*30 F2s 52 Pd4p *88 Th5d5 138 Sn4s 209 Ar4p1 303 Se A30 Na2p 53 Tm5s 88 Au4f5 138 Zn3s *212 Hf4d5 305 Pr4s30 Zr4p 53 Yb5s *88 Kr3d5 139 Xe4p 217 Kr3p1 *306 Ho4p332 Hf5p3 53 Zr4s *89 Zn3p3 *141 Gd4d *218 Pr4p3 *307 Rh3d5

318 Ge A 412 Cd3d3 548 Cu A *710 Fe2p3 885 Sn3s *1105 Ti A*319 Ar2s *412 Pb4d5 559 Pd3p1 711 Ni A 890 Ba A 1106 Cd A

319 Nd4s 415 Mo3p 563 Zn A 712 Cu A 893 Pb4s *1107 N A*320 Rb3s 416 Dy4s 566 Ta4s 714 Th4d3 894 Fe A 1108 Sm3d3*320 Er4p3 419 Ge A *568 Cu A *716 Sn3p3 900 Fe A *1113 Cd A

324 U5s *424 W4p3 570 Ti2s 718 Ag3s 900 Ce3d3 *1118 Ga2p3331 Pt4d3 *424 Ga A *571 Hg4p3 718 Ni A *904 Mn A 1125 La3p3332 Dy4p1 *432 Zr3s *573 Ag3p3 720 Cu A 905 Ba A 1128 Ag A

*332 Zr3p3 434 Pb4d3 *577 Cr2p3 *720 Co A 918 Cs A *1131 Eu3d5*335 Pd3d5 436 Ho4s *577 Te3d5 722 Tl4p1 929 Co2s *1134 Ag A*335 Th4f7 437 Hf4p1 577 Zn A 723 Fe2p1 930 I3p1 1137 Ba3p1*335 Au4d5 *439 Ca2s 577 Ir4p1 724 Pt4s *931 Pr3d5 1142 Xe3s*337 Tm4p 440 Ge A 585 Ru3s *724 Cs3d5 932 Cs A 1145 Ga2p1

340 Pd3d3 *440 Bi4d5 586 Cr2p1 738 Cs3d3 *932 Cu2p3 1152 Sc A342 As A *445 Re4p3 586 Zn A *738 U4d5 934 Xe3p3 *1159 Pd A343 Ho4p1 *445 In3d5 587 Te3d3 752 Nd A 939 Bi4s 1161 Eu3d3344 Th4f5 449 Er4s 593 W4s 758 Sn3p1 943 Xe A 1168 Th4p1346 Zr3p1 451 Ge A 595 Gd A 760 Au4s 946 Sb3s 1184 Ce3p3

*346 Yb4p5 453 In3d3 603 Ag3p1 763 Pb4p1 951 Pr3d3 *1186 Gd3d5348 Sm4s *458 Ti2p3 608 Pt4p1 767 Sb3p3 952 Mn A 1189 Rh A

*348 Ca2p3 *461 Ru3p3 609 Tl4p3 770 Mn2s 952 Cu2p1 1195 Zn2s*349 Ge A 464 Bi4d3 *618 Cd3p3 771 Cs3s *955 Xe A 1195 Ca A

351 Ca2p1 464 Ti2p1 *619 I3d5 778 Ni A *962 Cr A 1206 La3p1352 Mg A 465 Ta4p1 625 Re4s 780 U4d3 968 Th4p3 1215 Cs3s353 Au4d3 469 Nb3s 627 Cu A *781 Ba3d5 969 I A 1218 Gd3d3

*359 Lu4p3 *469 Os4p3 627 Rh3s *782 Co2p3 *977 O A 1218 Ru A*359 Sr3s 472 Tm4s 629 Ni A 782 Co A *980 I A *1221 Ge2p3

360 Eu4s 475 Zn A 630 I3d3 784 Ni A *981 Nd3d5 *1226 C A*360 Hg4d5 483 Ru3p1 632 V2s 788 Pr A 995 Xe3p1 *1236 K A*363 Nb3p3 *486 Sn3d5 635 Eu A *789 Fe A 997 Cs3p3 *1240 Tb3d5

366 Er4p1 487 Yb4s 639 Cu A 796 Ba3d3 999 O A 1243 Pr3p3367 As A 490 W4p1 *642 Mn2p3 797 Co2p1 1002 Cr A 1252 Ge2p1

*368 Ag3d5 492 Ga A 644 Pb4p3 800 Hg4s 1002 Te A *1270 Ar A374 Ag3d3 494 Sn3d3 645 Au4p1 806 Bi4p1 1005 Nd3d3 1272 Ce3p1376 Gd4s *495 Ir4p3 *646 Ni A 814 Sb3p1 1009 Ni2s 1273 U4p1

*377 K2s *496 Na A 647 Cu A 824 Te3p3 1011 Te3s 1276 Tb3d3378 As A *496 Rh3p3 652 Cd3p1 827 Ce A *1012 Te A 1293 Ba3s379 Nb3p1 *498 Zn A 653 Mn2p1 828 In 3s 1019 V A 1293 Dy3d5379 Hg4d3 500 Se2s 655 Os4s *831 F A *1022 Zn2p3 1300 Ga2s

*381 U4f7 506 Lu4s 657 Zn A *836 La3d5 1027 Sb A 1300 Th4s*381 Hf4p3 509 Ga A 664 Zn A 837 Co A *1035 Sb A 1301 Nd3p3

386 Tm4p 510 Mo3s *667 In3p3 843 Co A 1045 An2p1 1305 B A*386 Tl4d5 *517 B2p3 *668 Na A 846 Fe2s 1045 U4p3 *1305 Mg1s

392 U4f5 518 Re4p1 *669 Xe3d5 846 Fe A 1053 Sn A *1305 Cl A*396 Y3s *519 Pt4p3 670 Pd3s 846 Tl4s 1055 V A *1327 As2p3

397 Ga A 519 Ga A 673 Sm A 853 La3d3 *1059 V A 1332 Dy3d3*398 Mo3p 521 Rh3p1 677 Hg4p1 854 Mn A *1060 Sn A *1336 S A

398 Tb4s 524 V2p1 *677 Th4d5 *855 Ni2p3 1063 Cs3p1 1338 Pr3p1399 Yb4p1 *530 Sb3d5 679 Bi4p3 857 F A 1063 Ba3p3 *1351 Ho3d5

A = Auger Line, 1 = 1/2, 2 = 3/2, 3 = 5/2, 4 = 7/2.* one of the three most intense lines in the elemental spectrum, not including minor lines of spin doublets.

Identifying Unknown Peaks


XPS: Chemical State Determination – The Theory

• Small shifts in the core level binding energies are indicative of chemical state changes • Metal or oxide • Silica or silicone• Fluoride or fluorocarbon• C-C or C-O, C=O, C-F etc.

• Withdrawal of valence electron charge, decrease shielding = increase in BE

• Addition of valence electron charge, increase shielding = decrease in BE


XPS: Chemical State Determination – In Practice

• For most elements with uncomplicated peak-shapes, a binding energy reference is sufficient (e.g. NIST Database1 or Phi Handbook2)

• https://srdata.nist.gov/xps/main_search_menu.aspx

• Some things to watch for!• Check literature for calibration of instrument• Charge referencing

• External - Au 4f7/2 at 84.0 eV or 83.95 eV (ISO Standard)• Internal - C 1s at 285.0 eV or 284.8 eV (adventitious carbon) or 284.5 eV

(graphitic) • Internal – a known compound in the sample

1. http://srdata.nist.gov/xps/2. J.F.Moulder et.al. “Handbook of X-ray Photoelectron Spectroscopy” Perkin-Elmer Corp., Eden Prairie (1992).

https://srdata.nist.gov/xps/main_search_menu.aspx


Survey Scan

• Contaminated Polyurethane SurfaceBinding Energy (eV)

02004006008001000

CPS

F 1s

F K

LL

O K

LL

O 1

s

N 1

s

C 1

s

Si 2

s

Si 2

p

24.2 at.%15.2 at.%3.4 at. %56.8 at.%

0.5 at.%

Fluorine Oxygen Nitrogen CarbonSilicon

Zoom in and usebetter spectral resolution


High Resolution SpectraCarbon 1s

• Matched to Viton A – a type of fluorocarbonBinding Energy (eV)

282284286288290292294296

CPS

C-C, C-HC-OH, C-O-C, C*H2-CF2 O-C=O, -(CF)- -C*F2-CH2- -CF-C*F2-CF2- -CF3 C-(C*=O)-C


High Resolution Spectra• s orbital spectra – binding energy shift

gives most of the information• p, d and f orbital spectra…. ....Can get much more complicated!


Exercise – Survey Spectra • www.xpsfitting.com• Exercise 1 – Krytox – follow along…• Exercise 2 – unknown – give it a try…

http://www.xpsfitting.com/


Answer 2

Surface Science W estern

2

Cu

2s

Cu

2p

Cu

LMM

d

Cu

LMM

bC

u LM

M c

Cu

LMM

a

Cu

3s Cu

3p

C 1

s

N 1

s

O K

LL

O 1

s

O 2

sS 2s S 2p

NameCu 2p3/2O 1sN 1sC 1sCl 2pS 2p

Pos.928.00526.00395.00280.00194.00157.00

At%28.912.2

3.246.6

0.28.9

Cl 2

s

Cl 2

p

x 104

5

10

15

20

25

30

35

40

CPS

1200 1000 800 600 400 200 0Binding Energy (eV)

X-ray Photoelectron Spectroscopy (XPS)€¦ · Cu Lα 929.7 3.8 Mg Kα 1253.6 0.7 Al Kα 1486.6 0.85 Si Kα 1739.5 1.0 Y Lα 1922.6 1.5 Zr Lα 2042.4 1.7 Ti Kα 4510.0 2.0 Cr Kα

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