Basic XPS Information Section

The Basic XPS Information Section provides fundamental XPS spectra, BE values, FWHM values, BE tables, overlays of key spectra, histograms and a table of XPS parameters.
The Advanced XPS Information Section is a collection of additional spectra, overlays of spectra, peak-fit advice, data collection guidance, material info,
common contaminants, degradation during analysis, auto-oxidation, gas capture study, valence band spectra, Auger spectra, and more.
Published literature references, and website links are summarized at the end of the advanced section.
→  Periodic Table – HomePage                    XPS Database of Polymers                 → Six (6) BE Tables

 

Cadmium (Cd)

 

Greenockite – CdS Cadmium – Cdo Monteponite – CdO

 

  Page Index
  • Expert Knowledge & Explanations


Cadmium (Cdo) Metal

Peak-fits, BEs, FWHMs, and Peak Labels

  .
Cadmium (Cdo) Metal
Cd (3d) Spectrum – raw spectrum
ion etched clean		 Cadmium (Cdo) Metal
Peak-fit of Cd (3d) Spectrum
w/o asymm
→  Periodic Table – HomePage    
Cadmium (Cdo) Metal
Cd (3d) Spectrum – extended range 
 Cadmium (Cdo) Metal
Peak-fit of Cd (3d) Spectrum (w asymm)

 

.
Cadmium (Cdo) Metal
Cd (4s) Spectrum		 Cadmium (Cdo) Metal
Cd (4p) Spectrum
   

 


Survey Spectrum of Cadmium (Cdo) Metal
with Peaks Integrated, Assigned and Labelled

 

 

→  Periodic Table 

XPS Signals for Cadmium, (Cdo) Metal

Spin-Orbit Term,  BE (eV) Value, and Scofield σ for Aluminum Kα X-rays (1486 eV, 8.33 Ang)

Overlaps Spin-Orbit Term BE (eV) Value Scofield σ from 1486 eV X-rays IMFP (TPP-2M) in Å
  Cd (3s) 772 3.04 12.6
  Cd (3p1/2) 653 4.22 14.5
I (3d) overlaps Cd (3p3/2) 619 8.50 14.5
  Cd (3d3/2) 413 8.27 17.0
N (1s) & Sc (2p) overlap Cd (3d5/2) 405.02 11.95 17.0
Ga (3p) overlaps Cd (4s) 110 0.692 20.5
Al (2p) overlaps Cd (4p) 69  2.25 20.9

σ:  abbreviation for the term Scofield Photoionization Cross-Section which are used with IMFP and TF to generate RSFs and atom% quantitation

Plasmon Peaks

Auger Peaks

 Intrinsic Plasmon Peak:  ~xx eV above peak max
Expected Bandgap for CdO:  2.2 – 2.5 eV
Work Function for CdO:  xx eV

*Scofield Cross-Section (σ) for C (1s) = 1.0

→  Periodic Table 

 

Cd (4s) and (4p) Spectra from Cdo Metal
Fresh exposed bulk produced by extensive Ar+ ion etching

Cd (4s) and Cd (4p)
(part of study for one electron breakdown)

 

Valence Band Spectrum from Cadmium, Cdo Metal
 Fresh exposed bulk produced by extensive Ar+ ion etching

 

 

Plasmon Peaks from Cdo Metal
 Fresh exposed bulk produced by extensive Ar+ ion etching

Cd (3d) – Extended Range Spectrum Cd (3d) – Extended Range Spectrum – Vertically Zoomed
→  Periodic Table 

 

Cd (LMM) Auger Peaks from Cdo Metal
 Fresh exposed bulk produced by extensive Ar+ ion etching
Cdo Metal – main Auger peak Cdo Metal – full Auger range

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Artefacts Caused by Argon Ion Etching

Cadmium Carbide(s)

can form when ion etched Reactive Metal Surfaces capture
Residual UHV Gases (CO, H2O, CH4 etc)

Argon Trapped in Cdo

can form when Argon Ions are used
to removed surface contamination
   

 

Survey Spectrum of Cd Native Oxide
with Peaks Integrated, Assigned and Labelled

 

 

Side-by-Side Comparison of
Cd Native Oxide & Cadmium Oxide (CdO)
Peak-fits, BEs, FWHMs, and Peak Labels
Cd Native Oxide CdO
Cd (3d) from Cd Native Oxide
Flood Gun OFF
As-Measured, C (1s) at 285.7 eV 		 Cd (3d) from CdO – pressed powder
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

→  Periodic Table   
Cd Native Oxide CdO
C (1s) from Cd Native Oxide
As-Measured, C (1s) at 285.7 eV
Flood Gun OFF

C (1s) from CdO – pressed powder
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

→  Periodic Table 
  
Cd Native Oxide CdO
O (1s) from Cd Native Oxide
As-Measured, C (1s) at 285.7 eV
Flood Gun OFF

O (1s) from CdO – pressed powder
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

 
→  Periodic Table 
Cd Native Oxide CdO
Cd (LMM) Auger Peaks from Cd Native Oxide
As-Measured, C (1s) at 285.7 eV
Flood Gun OFF

Cd (LMM) Auger Peaks from CdO – pellet or fresh bulk
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

 

 

 

Survey Spectrum of Cadmium Oxide (CdO)
with Peaks Integrated, Assigned and Labelled

 


→  Periodic Table  

 

Overlays of Cd (3d) Spectra for
Cd Native Oxide and Cadmium Oxide

Caution: BEs from Grounded Native Oxides can be Misleading if Flood Gun is ON

 Overlay of Cdo metal and Cd Native Oxide – Cd (3d)
Native Oxide C (1s) = 285.7 eV
Flood gun OFF

  Overlay of Cdo metal and CdO – Cd (3d)
Pure Oxide C (1s) = 285.0 eV
Chemical Shift: xx
→  Periodic Table  Copyright ©:  The XPS Library 

 

Overlay of Cd (3d)
Cdo Metal, native Cd oxide & Cadmium Oxide, CdO

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Valence Band Spectra
Cdo, CdO 

Cdo
Ion etched clean		 CdO – pellet
Flood gun is ON,  Charge referenced so C (1s) = 285.0 eV

Overlay of Valence Band Spectra
for Cdo metal and CdO

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Survey Spectrum of Cadmium Sulfide (CdS)
with Peaks Integrated, Assigned and Labelled

 

 

Side-by-Side Comparison of
CdO & CdS
Cadmium Oxide & Cadmium Sulfide
Peak-fits, BEs, FWHMs, and Peak Labels
CdO CdS
Cd (3d) from CdO
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Cd (3d) from CdS – single crystal
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

→  Periodic Table 
  
CdO CdS
C (1s) from CdO
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

C (1s) from CdS – single crystal
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

→  Periodic Table 
  . 
CdO CdS
O (1s) from CdO
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

O (1s) from CdS – single crystal
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

→  Periodic Table

 
.
CdO CdS
Cd (LMM) Auger Peaks from CdO
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

Cd (LMM) Auger Peaks from CdS – single crystal
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

→  Periodic Table  

 

Overlays of Cd (3d) Spectra for
Cdo metal and CdO or CdS

Caution: BEs from Grounded Native Oxides can be Misleading if Flood Gun is ON

 Overlay of Cdo metal and CdO – Cd (3d)
Flood gun is ON,  CdO Charge referenced so C (1s) = 285.0 eV
  Overlay of Cdo metal and CdS – Cd (3d)
Flood gun is ON,  CdS Charge referenced so C (1s) = 285.0 eV
→  Periodic Table  Copyright ©:  The XPS Library 

 

Overlay of Cd (3d)
Cdo Metal, CdO & CdS  

 

 

Expanded Overlay of Cd (3d5/2)
 CdO & CdS  

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Valence Band Spectra
CdO, CdS

CdO
Flood gun is ON,  Charge referenced so C (1s) = 285.0 eV		 CdS – single crystal
Flood gun is ON,  Charge referenced so C (1s) = 285.0 eV

Overlay of Valence Band Spectra
for CdO and CdS

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

 

Cadmium Minerals, Gemstones, and Chemical Compounds

 
Keyite – Cu3Zn4Cd2(AsO4)6 · 2H2O Otavite – CdCO3 Birchite – Cd2Cu2(PO4)2(SO4) · 5H2O Cadmoindite – CdIn2S4

→  Periodic Table 

 

 

Six (6) Chemical State Tables of Cd (3d5/2) BEs

 

  • The XPS Library Spectra-Base
  • PHI Handbook
  • Thermo-Scientific Website
  • XPSfitting Website
  • Techdb Website
  • NIST Website

→  Periodic Table 

 

Notes of Caution when using Published BEs and BE Tables from Insulators and Conductors:

  • Accuracy of Published BEs
    • The accuracy depends on the calibration BEs used to calibrate the energy scale of the instrument.  Cu (2p3) BE can vary from 932.2 to 932.8 eV for old publications 
    • Different authors use different BEs for the C (1s) BE of the hydrocarbons found in adventitious carbon that appears on all materials and samples.  From 284.2 to 285.3 eV
    • The accuracy depends on when the authors last checked or adjusted their energy scale to produce the expected calibration BEs
  • Worldwide Differences in Energy Scale Calibrations
    • For various reasons authors still use older energy scale calibrations 
    • Some authors still adjust their energy scale so Cu (3d5/2) appears at 932.2 eV or 932.8 eV because this is what the maker taught them
    • This range causes BEs in the higher BE end to be larger than expected 
    • This variation increases significantly above 600 eV BE
  • Charge Compensation
    • Samples that behave as true insulators normally require the use of a charge neutralizer (electron flood gun with or without Ar+ ions) so that the measured chemical state spectra can be produced without peak-shape distortions or sloping tails on the low BE side of the peak envelop. 
    • Floating all samples (conductive, semi-conductive, and non-conductive) and always using the electron flood gun is considered to produce more reliable BEs and is recommended.
  • Charge Referencing Methods for Insulators
    • Charge referencing is a common method, but it can produce results that are less reliable.
    • When an electron flood gun is used, the BE scale will usually shift to lower BE values by 0.01 to 5.0 eV depending on your voltage setting. Normally, to correct for this flood gun induced shift, the BE of the hydrocarbon C (1s) peak maximum from adventitious carbon is used to correct for the charge induced shift.
    • The hydrocarbon peak is normally the largest peak at the lowest BE. 
    • Depending on your preference or training, the C (1s) BE assigned to this hydrocarbon peak varies from 284.8 to 285.0 eV.  Other BEs can be as low as 284.2 eV or as high as 285.3 eV
    • Native oxides that still show the pure metal can suffer differential charging that causes the C (1s) and the O (1s) and the Metal Oxide BE to be larger
    • When using the electron flood gun, the instrument operator should adjust the voltage and the XY position of the electron flood gun to produce peaks from a strong XPS signal (eg O (1s) or C (1s) having the most narrow FWHM and the lowest experimentally measured BE. 

→  Periodic Table 

Table #1

Cd (3d5/2) Chemical State BEs from:  “The XPS Library Spectra-Base”

C (1s) BE = 285.0 eV for TXL BEs
and C (1s) BE = 284.8 eV for NIST BEs

Element Atomic # Compound As-Measured by TXL or NIST Average BE Largest BE Hydrocarbon C (1s) BE  Source
Cd 48 Cd-O2 (N*1) 403.6 eV   284.8 eV Avg BE – NIST
Cd 48 Cd-2O 404.1 eV   285.0 eV The XPS Library
Cd 48 CdO (N*9) 404.2 eV 404.6 eV 284.8 eV Avg BE – NIST
Cd 48 Cd-2O (N*1) 404.6 eV   284.8 eV Avg BE – NIST
Cd 48 Cd-Se 404.7 eV 405.2 eV 285.0 eV The XPS Library
Cd 48 Cd-(OH)2 (N*2) 404.8 eV 405.1 eV 284.8 eV Avg BE – NIST
Cd 48 CdTe (N*10) 404.9 eV 405.2 eV 284.8 eV Avg BE – NIST
Cd 48 Cd- element 405.0 eV   285.0 eV The XPS Library
Cd 48 CdSe (N*2) 405.0 eV 405.3 eV 284.8 eV Avg BE – NIST
Cd 48 Cd-Te 405.0 eV 405.1 eV 285.0 eV The XPS Library
Cd 48 Cd-S (N*7) 405.1 eV 405.5 eV 284.8 eV Avg BE – NIST
Cd 48 Cd-CO3 405.2 eV   285.0 eV The XPS Library
Cd 48 HgCdTe (N*3) 405.2 eV 405.3 eV 284.8 eV Avg BE – NIST
Cd 48 Cd-I2 (N*3) 405.4 eV 405.8 eV 284.8 eV Avg BE – NIST
Cd 48 CdS 405.5 eV   285.0 eV The XPS Library
Cd 48 Cd-F2 (N*5) 405.6 eV 406.2 eV 284.8 eV Avg BE – NIST
Cd 48 CdBr2 (N*1) 405.7 eV 406.0 eV 284.8 eV Avg BE – NIST

Charge Referencing Notes

  • (N*number) identifies the number of NIST BEs that were averaged to produce the BE in the middle column.
  • The XPS Library uses Binding Energy Scale Calibration with Cu (3d5/2) BE = 932.62 eV and Au (4f7/2) BE = 83.98 eV.  BE (eV) Uncertainty Range:  +/- 0.2 eV
  • Charge Referencing of insulators is defined such that the Adventitious Hydrocarbon C (1s) BE (eV) = 285.0 eV.  NIST uses C (1s) BE = 284.8 eV 
  • Note:   Ion etching removes adventitious carbon, implants Ar (+), changes conductivity of surface, and degrades chemistry of various chemical states.
  • Note:  Ion Etching changes BE of C (1s) hydrocarbon peak.
  • TXL – abbreviation for: “The XPS Library” (https://xpslibrary.com).  NIST:  National Institute for Science and Technology (in USA)

→  Periodic Table 

Table #2

Cd (3d5/2) Chemical State BEs from:  “PHI Handbook”

C (1s) BE = 284.8 eV

→  Periodic Table 

Copyright ©:  Ulvac-PHI

Table #3

Cd (3d5/2) Chemical State BEs from:  “Thermo-Scientific” Website

C (1s) BE = 284.8 eV

Chemical state Binding energy (eV), Cd (3d5)
Cd metal 405.1 eV
CdS 405.1 eV

→  Periodic Table 

Copyright ©:  Thermo Scientific 

Table #4

Cd (3d5/2) Chemical State BEs from:  “XPSfitting” Website

Chemical State BE Table derived by Averaging BEs in the NIST XPS database of BEs
C (1s) BE = 284.8 eV

→  Periodic Table 

Copyright ©:  Mark Beisinger

Table #5

Cd (3d5/2) Chemical State BEs from:  “Techdb.podzone.net” Website

 

XPS Spectra – Chemical Shift | Binding Energy
C (1s) BE = 284.6 eV

XPS(X線光電子分光法)スペクトル 化学状態 化学シフト ケミカルシフト

Element Level Compound B.E.(eV) min   max
Cd 3d5/2 CdO2 404.0 ±0.3 403.7 ～ 404.2
Cd 3d5/2 Hg0.8Cd0.2Te 404.7 ±0.2 404.5 ～ 404.9
Cd 3d5/2 CdTe 405.0 ±0.2 404.8 ～ 405.2
Cd 3d5/2 Cd(OH)2 405.0 ±0.3 404.7 ～ 405.3
Cd 3d5/2 Cd 405.1 ±0.3 404.8 ～ 405.3
Cd 3d5/2 CdCO3 405.1 ±0.3 404.8 ～ 405.3
Cd 3d5/2 CdO 405.2 ±0.3 404.9 ～ 405.4
Cd 3d5/2 CdSe 405.3 ±0.3 405.0 ～ 405.5
Cd 3d5/2 CdS 405.3 ±0.3 405.0 ～ 405.5
Cd 3d5/2 Halides 405.8 ±0.4 405.4 ～ 406.1

 

→  Periodic Table 

 

 

Histograms of NIST BEs for Cd (3d5/2) BEs

Important Note:  NIST Database defines Adventitious Hydrocarbon C (1s) BE = 284.8 eV for all insulators.

Histogram indicates:  404.9 eV for Cdo based on 10 literature BEs Histogram indicates:  404.6 eV for CdO based on 9 literature BEs

Histogram indicates:  405.3 eV for CdS based on 7 literature BEs Histogram indicates:  405.1 eV for CdTe based on 12 literature BEs  

Table #6


NIST Database of Cd (3d5/2) Binding Energies

NIST Standard Reference Database 20, Version 4.1

Data compiled and evaluated
by
Alexander V. Naumkin, Anna Kraut-Vass, Stephen W. Gaarenstroom, and Cedric J. Powell
©2012 copyright by the U.S. Secretary of Commerce on behalf of the United States of America. All rights reserved.

Important Note:  NIST Database defines Adventitious Hydrocarbon C (1s) BE = 284.8 eV for all insulators.

Element Spectral Line Formula Energy (eV) Reference
Cd 3d5/2 CdO2 403.60  Click
Cd 3d5/2 CdO 404.00  Click
Cd 3d5/2 Cd2SnO4 404.14  Click
Cd 3d5/2 CdO 404.20  Click
Cd 3d5/2 CdO 404.20  Click
Cd 3d5/2 CdO 404.20  Click
Cd 3d5/2 CdO 404.20  Click
Cd 3d5/2 CdO 404.20  Click
Cd 3d5/2 CdO 404.20  Click
Cd 3d5/2 Cd2SnO4 404.50  Click
Cd 3d5/2 Cd 404.60  Click
Cd 3d5/2 Cd 404.60  Click
Cd 3d5/2 Cd0.2Hg0.8Te 404.60  Click
Cd 3d5/2 CdSnO3 404.60  Click
Cd 3d5/2 CdO 404.60  Click
Cd 3d5/2 Cd2O 404.60  Click
Cd 3d5/2 Cd2SnO4 404.60  Click
Cd 3d5/2 CdRh2O4 404.70  Click
Cd 3d5/2 Cd 404.78  Click
Cd 3d5/2 CdTe 404.80  Click
Cd 3d5/2 Cd(OH)2 404.80  Click
Cd 3d5/2 Cd(OH)2 404.80  Click
Cd 3d5/2 [Cd((C5H11)2NC(S)S)2] 404.80  Click
Cd 3d5/2 Cd0.65Zn0.35TeOx 404.80  Click
Cd 3d5/2 CdSe0.65Te0.35 404.90  Click
Cd 3d5/2 Cd 404.90  Click
Cd 3d5/2 Cd 404.90  Click
Cd 3d5/2 Cd99.6Sn0.4 404.92  Click
Cd 3d5/2 CdTe 404.93  Click
Cd 3d5/2 CdTe 404.94  Click
Cd 3d5/2 CdTe 404.98  Click
Cd 3d5/2 Cd 405.00  Click
Cd 3d5/2 Cd 405.00  Click
Cd 3d5/2 CdTe 405.00  Click
Cd 3d5/2 CdSe 405.00  Click
Cd 3d5/2 Zn0.30Cd0.70Se 405.00  Click
Cd 3d5/2 Zn0.42Cd0.58Se 405.00  Click
Cd 3d5/2 Zn0.70Cd0.30Se 405.00  Click
Cd 3d5/2 Cd 405.04  Click
Cd 3d5/2 CdTe 405.08  Click
Cd 3d5/2 CdTe 405.08  Click
Cd 3d5/2 CdCO3 405.10  Click
Cd 3d5/2 CdTe 405.10  Click
Cd 3d5/2 Cd(OH)2 405.10  Click
Cd 3d5/2 CdS 405.10  Click
Cd 3d5/2 Zn0.10Cd0.90Se 405.10  Click
Cd 3d5/2 Zn0.50Cd0.50Se 405.10  Click
Cd 3d5/2 Zn0.90Cd0.10Se 405.10  Click
Cd 3d5/2 Cd 405.11  Click
Cd 3d5/2 Cd 405.15  Click
Cd 3d5/2 CdTe 405.15  Click
Cd 3d5/2 CdTe 405.20  Click
Cd 3d5/2 CdTe 405.20  Click
Cd 3d5/2 CdS 405.20  Click
Cd 3d5/2 Cd0.28Hg0.72Te 405.20  Click
Cd 3d5/2 CdSe 405.20  Click
Cd 3d5/2 Cd 405.30  Click
Cd 3d5/2 CdS 405.30  Click
Cd 3d5/2 CdS 405.30  Click
Cd 3d5/2 CdSe 405.30  Click
Cd 3d5/2 Cd2SnO2 405.30  Click
Cd 3d5/2 Cd0.33Hg0.67Te 405.30  Click
Cd 3d5/2 Cd0.11Hg0.89Te 405.34  Click
Cd 3d5/2 Cd0.45Hg0.55Te 405.34  Click
Cd 3d5/2 CdTe 405.35  Click
Cd 3d5/2 CdI2 405.40  Click
Cd 3d5/2 CdSO4 405.40  Click
Cd 3d5/2 CdCr0.3In1.7S4 405.40  Click
Cd 3d5/2 CdCr0.3In1.7S4 405.40  Click
Cd 3d5/2 CdS 405.40  Click
Cd 3d5/2 CdS 405.40  Click
Cd 3d5/2 CdS 405.40  Click
Cd 3d5/2 CdTe 405.50  Click
Cd 3d5/2 CdTeO3 405.50  Click
Cd 3d5/2 CdS 405.50  Click
Cd 3d5/2 CdF2 405.60  Click
Cd 3d5/2 CdF2 405.60  Click
Cd 3d5/2 CdI2 405.70  Click
Cd 3d5/2 (CdCl2)2.5H2O 405.70  Click
Cd 3d5/2 CdBr2.4H2O 405.70  Click
Cd 3d5/2 CdS 405.73  Click
Cd 3d5/2 [CdCl2(H2NC(O)NHC(O)NH2)2] 405.80  Click
Cd 3d5/2 CdI2 405.80  Click
Cd 3d5/2 CdF2 405.80  Click
Cd 3d5/2 CdIn2S2Se2 405.80  Click
Cd 3d5/2 [CdCl2(P(C6H5)3)3] 405.90  Click
Cd 3d5/2 CdF2 405.90  Click
Cd 3d5/2 CdBr2 406.00  Click
Cd 3d5/2 CdCl2 406.10  Click
Cd 3d5/2 CdF2 406.20  Click
Cd 3d5/2 Cd(NO3)2 406.20  Click
Cd 3d5/2 Ba/Ca/Cd/Sr/in_montmorillonite 406.40  Click
Cd 3d5/2 CdPdF4 406.70  Click
Cd 3d5/2 CdO 407.38  Click

 

 

Statistical Analysis of Binding Energies in NIST XPS Database of BEs

 

 

→  Periodic Table 

 

Advanced XPS Information Section

Expert Knowledge, Spectra, Features, Guidance and Cautions
for XPS Research Studies on Cadmium Materials

 

 

 

Expert Knowledge Explanations

→  Periodic Table 

 

Cadmium Chemical Compounds


Peak-fits and Overlays of Chemical State Spectra

Pure Cadmium, Cdo:  Cd (3d)
Cu (2p3/2) BE = 932.6 eV		 CdO:  Cd (3d)
C (1s) BE = 285.0 eV		 CdS:  Cd (3d)
C (1s) BE = 285.0 eV

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Overlay of Cd (3d) Spectra shown Above

C (1s) BE = 285.0 eV

 

Chemical Shift between Cd and CdO:  -0.8 eV
 Chemical Shift between Cd and CdS:  +0.4 eV

 

→  Periodic Table 

 


Cadmium Oxide (CdO)
pressed powder

Survey Spectrum from CdO
Flood gun is ON, C (1s) BE = 285.0 eV
 Cd (3d) Chemical State Spectrum from CdO
Flood gun is ON, C (1s) BE = 285.0 eV
→  Periodic Table 
  
O (1s) Chemical State Spectrum from CdO
Flood gun is ON, C (1s) BE = 285.0 eV
 C (1s) Chemical State Spectrum from CdO
Flood gun is ON, C (1s) BE = 285.0 eV
→  Periodic Table 
  
Valence Band Spectrum from CdO
Flood gun is ON, C (1s) BE = 285.0 eV
 Auger Signals from CdO
Flood gun is ON, C (1s) BE = 285.0 eV
 

 

Multiplet Splitting Features
for Cadmium Compounds

Cd metal – NO Splitting for Cd (4s) CdO – NO Splitting for Cd (4s)

 

 

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

 

 

Cadmium Chemical Compounds

   
   
   

→  Periodic Table 

 

Quantitation Details and Information

Quantitation by XPS is often incorrectly done, in many laboratories, by integrating only the main peak, ignoring the Electron Loss peak, and the satellites that appear as much as 30 eV above the main peak.  By ignoring the electron loss peak and the satellites, the accuracy of the atom% quantitation is in error.

When using theoretically calculated Scofield cross-section values, the data must be corrected for the transmission function effect, use the calculated TPP-2M IMFP values, the pass energy effect on the transmission function, and the peak area used for calculation must include the electron loss peak area, shake-up peak area, multiplet-splitting peak area, and satellites that occur within 30 eV of the main peak.

 

Quantitation from Pure, Homogeneous Binary Compound
composed of Cadmium – CdO

This section is focused on measuring and reporting the atom % quantitation that results by using:

  • Scofield cross-sections,
  • Spectra corrected to be free from Transmission Function effects
  • A Pass Energy that does not saturate the detector system in the low KE range (BE = 1000-1400 eV)
  • A focused beam of X-ray smaller than the field of view of the lens
  • An angle between the lens and the source that is ~55 deg that negates the effects of beta-asymmetry
  • TPP-2M inelastic mean free path values, and
  • Either a linear background or an iterated Shirley (Sherwood-Proctor) background to define peak areas

The results show here are examples of a method being developed that is expected to improve the “accuracy” or “reliability” of the atom % values produced by XPS.

 

→  Periodic Table 

 

 

Flood Gun Effect on Native Oxide of Cadmium

 

Native Oxide of Cadmium Sheet – Sample GROUNDED
versus
Native Oxide of Cadmium Sheet – Sample FLOATING

 

 

Native Oxide of Cadmium Sheet – Sample Grounded

Electron Flood Gun:  0 Voltage (FG OFF), Min Voltage versus Max Voltage

Cd (3d5/2) O (1s) C (1s)
     
→  Periodic Table     

 

Native Oxide of Cadmium Sheet – Sample Floating

Electron Flood Gun:  0 Voltage (FG OFF), Min Voltage versus Max Voltage

Cd (3d5/2) O (1s) C (1s)
     
     

→  Periodic Table 

 

 

XPS Study of UHV Gas Captured by Freshly Ion Etched Cadmium
 
Reveals Chemical Shifts and Chemical States that Develop from Highly Reactive Pure Cdo

Surface was strongly Ar+ ion etched to remove all contaminants, and
then allowed to react overnight with the UHV Gases – CO, H2, H2O, O2 & CH4
that normally reside inside on the walls of the chamber, on the sample stage,
and on the nearby un-etched surface a total of 10-14 hours.  UHV pump was a Cryopump.
Initial spectra are at the front.  Final spectra are at the rear. Flood gun is OFF.
 
 
 
Cd (3d) Signal
  O (1s) Signal C (1s) Signal
     
 
 
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AES Study of UHV Gas Captured by Freshly Ion Etched Cadmium

Cadmium sheet was ion etched and allowed to react with residual UHV gases overnight – ~14 hr run.

Cd (LMM) Signal:
Cd at front -> CdO X at rear 
Cd KE = 373.4 eV,   		 O (KLL) Signal:
Cd at front -> CdO X at rear 
O KE = 511.7 eV		 C (KLL) Signal:

O KE =274.6eV
   
     
   

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Cadmium Alloys

   
XxCu XxCu
→  Periodic Table   
XxCu XxCu

 

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XPS Facts, Guidance & Information

→  Periodic Table 

    Element   Cadmium (Cd)
  
    Primary XPS peak used for Peak-fitting:   Cd (3d5/2)  
    Spin-Orbit (S-O) splitting for Primary Peak:   Spin-Orbit splitting for “d” orbital, ΔBE = 6.8 eV
  
    Binding Energy (BE) of Primary XPS Signal:   405 eV
  
    Scofield Cross-Section (σ) Value:   Cd (3d5/2) = 11.95     Cd (3d3/2) = 8.27
  
    Conductivity:   Cd resistivity =  
Native Oxide suffers Differential Charing		  
    Range of Cd (3d5/2) Chemical State BEs:   404 – 407 eV range   (Cdo to CdF2)  
    Signals from other elements that overlap
Cd (3d5/2) Primary Peak:		   N (1s)  
    Bulk Plasmons:   ~xx eV above peak max for pure  
    Shake-up Peaks:   xx  
    Multiplet Splitting Peaks:   xx  

 

 

 General Information about
XXX Compounds:		   xx  
    Cautions – Chemical Poison Warning  

xx 

  

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Information Useful for Peak-fitting Cd (3d5/2)

  • FWHM (eV) of Cd (3d5/2) for Pure Cdo :  ~0.6 eV using 25 eV Pass Energy after ion etching:
  • FWHM (eV) of Cd (3d5/2) for CdO:  ~1.4 eV using 50 eV Pass Energy  (before ion etching)
  • Binding Energy (BE) of Primary Signal used for Measuring Chemical State Spectra:  404 eV for Cd (3d5/2) with +/- 0.2 uncertainty
  • List of XPS Peaks that can Overlap Peak-fit results for Cd (3d5/2):  N (1s)

→  Periodic Table 

 

General Guidelines for Peak-fitting XPS Signals

  • Typical Energy Resolution for Pass Energy (PE) setting used to measure Chemical State Spectra on Various XPS Instruments
    • Ag (3d5/2) FWHM (eV) = ~0.95 eV for PE 50 on Thermo K-Alpha
    • Ag (3d5/2) FWHM (eV) = ~1.00 eV for PE 80 on Kratos Nova
    • Ag (3d5/2) FWHM (eV) = ~0.95 eV for PE 45 on PHI VersaProbe
  • FWHM (eV) of Pure Elements: Ranges from 0.4 to 1.0 eV across the periodic table
  • FWHM of Chemical State Peaks in any Chemical Compound:  Ranges from 1.1 to 1.6 eV  (in rare cases FWHM can be 1.8 to 2.0 eV)
  • FWHM of Pure Element versus FWHM of Oxide:  Pure element FWHM << Oxide FWHM  (e.g. 0.8 vs 1.5 eV, roughly 2x)
  • If FWHM Greater than 1.6 eV:  When a peak FWHM is larger than 1.6 eV, it is best to add another peak to the peak-fit envelop.
  • BE (eV) Difference in Chemical States: The difference in chemical state BEs is typically 1.0-1.3 eV apart.  In rare cases, <0.8 eV.
  • Number of Peaks to Use:  Use minimum. Do not use peaks with FWHM < 1.0 eV unless it is a or a conductive compound.
  • Typical Peak-Shape:  80% G: 20% L,   or Voigt : 1.4 eV Gaussian and 0.5 eV Lorentzian
  • Spin-Orbit Splitting of Two Peaks (due to Coupling):  The ratio of the two (2) peak areas must be constrained.

Notes:

  • Other Oxidation States can appear as small peaks when peak-fitting
  • Pure element signals normally have asymmetric tails that should be included in the peak-fit.
  • Gaseous state materials often display asymmetric tails due to vibrational broadening.
  • Peak-fits of C (1s) in polymers include an asymmetric tail when the energy resolution is very high.
  • Binding energy shifts of some compounds are negative due to unusual electron polarization.

→  Periodic Table 

 

Contaminants Specific to Cadmium

  • Cadmium develops a thick native oxide due to the reactive nature of clean Cadmium.
  • The native oxide of Cd Ox is 4-6 nm thick.
  • Cadmium thin films often have a low level of iron (Fe) in the bulk as a contaminant or to strengthen the thin film
  • Cadmium forms a low level of carbide when the surface is ion etched inside the analysis chamber

 

Commonplace Contaminants

  • Carbon and Oxygen are common contaminants that appear on nearly all surfaces. The amount of Carbon usually depends on handling.
  • Carbon is usually the major contaminant.  The amount of carbon ranges from 5-50 atom%.
  • Carbon contamination is attributed to air-borne organic gases that become trapped by the surface, oils transferred to the surface from packaging containers, static electricity, or handling of the product in the production environment.
  • Carbon contamination is normally a mixture of different chemical states of carbon (hydrocarbon, alcohol or ether, and ester or acid).
  • Hydrocarbon is the dominant form of carbon contamination. It is normally 2-4x larger than the other chemical states of carbon.
  • Carbonate peaks, if they appear, normally appear ~4.5 eV above the hydrocarbon C (1s) peak max BE.
  • Low levels of carbonate is common on many s that readily oxidize in the air.
  • High levels of carbonate appear on reactive oxides and various hydroxides.  This is due to reaction between the oxide and CO2 in the air.
  • Hydroxide contamination peak is due to the reaction with residual water in the lab air or the vacuum.
  • The O (1s) BE of the hydroxide (water) contamination normally appears 0.5 to 1.0 eV above the oxide peak
  • Sodium (Na), Potassium (K), Sulfur (S) and Chlorine (Cl) are common trace to low level contaminants
  • To find low level contaminants it is very useful to vertically expand the 0-600 eV region of the survey spectrum by 5-10X
  • A tiny peak that has 3 or more adjacent data-points above the average noise of the background is considerate to be a real peak
  • Carbides can appear after ion etching various reactive s.  Carbides form due to the residual CO and CH4 in the vacuum.
  • Ion etching can produce low oxidation states of the material being analyzed.  These are newly formed contaminants.
  • Ion etching polymers by using standard Ar+ ion guns will destroy the polymer, converting it into a graphitic type of carbon

→  Periodic Table 

 

Data Collection Guidance

  • Chemical state differentiation can be difficult
  • Collect principal Cd (3d) peak as well as Cd (3p).
  • Long time exposures (high dose) to X-rays can degrade various polymers, catalysts, high oxidation state compounds
  • During XPS analysis, water or solvents can be lost due to high vacuum or irradiation with X-rays or Electron flood gun
  • Auger signals can sometimes be used to discern chemical state shifts when XPS shifts are very small

→  Periodic Table 

 

Data Collection Settings for Cadmium (Cd)

  • Conductivity:  Cadmium readily develops a native oxide that is sensitive to Flood Gun – Differential Charging Possible – float sample recommended
  • Primary Peak (XPS Signal) used to measure Chemical State Spectra:  Cd (3d5/2) at 401 eV
  • Recommended Pass Energy for Measuring Chemical State Spectrum:  40-50 eV    (Produces Ag (3d5/2) FWHM ~0.7 eV)
  • Recommended # of Scans for Measuring Chemical State Spectrum:  4-5 scans normally   (Use 10-25 scans to improve S/N)
  • Dwell Time:  50 msec/point
  • Step Size:  0.1 eV/point   (0.1 eV/step or 0.1 eV/channel)
  • Standard BE Range for Measuring Chemical State Spectrum:  390-420eV
  • Recommended Extended BE Range for Measuring Chemical State Spectrum:  380-480eV
  • Recommended BE Range for Survey Spectrum:  -10 to 1,100 eV   (above 1,100 eV there are no useful XPS signals, except for Ge and Ga)
  • Typical Time for Survey Spectrum:  3-5 minutes for newer instruments, 5-10 minutes for older instruments
  • Typical Time for a single Chemical State Spectrum with high S/N:  5-10 minutes for newer instruments, 10-15 minutes for older instruments 

→  Periodic Table 

 

Effects of Argon Ion Etching

  • Carbides appear after ion etching Cd and various reactive surfaces.  Carbides form due to the presence of residual CO and CH4 in the vacuum.
  • Ion etching can produce low oxidation states of the material being analyzed.  These are newly formed contaminants.
  • Ion etching polymers by using standard Ar+ ion guns will destroy the polymer, converting it into a graphitic type of carbon

 

→  Periodic Table 

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Gas Phase XPS or UPS Spectra
 
 
     
     
     
     
     
     
     
     
     
 
 
 
 

 

Chemical State Spectra from Literature
 
 
xxx
 

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