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

 

Cesium (Cs)

 

Galkhaite – (Hg5Cu)CsAs4S12 Cesium Metal – Cso Londonite – (Cs)Al4Be(B,Be)12O28

 

  Page Index
  • Expert Knowledge & Explanations


Cesium (Cso) Metal
Peak-fits, BEs, FWHMs, and Peak Labels

  .
Cesium (Cso) Metal
Cs (3d) Spectrum – raw spectrum		 Cesium (Cso) Metal
Peak-fit of Cs (3d) Spectrum (w/o asymm)
→  Periodic Table – HomePage  
Cesium (Cso) Metal
Cs (3d) Spectrum – extended range 
 Cesium (Cso) Metal
Peak-fit of Cs (3d) Spectrum (w asymm)
   

 

Survey Spectrum of Cesium (Cso) Metal

with Peaks Integrated, Assigned and Labelled

 

→  Periodic Table 

XPS Signals for Cesium, (Cso) 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
  Cs (3s) 1217 3.73 25.5
  Cs (3p1/2) 1065 5.29 39.5
  Cs (3p3/2) 998 11.38 39.5
  Cs (3d3/2) 740 16.46 55.7
  Cs (3d5/2) 726.22 23.76 55.7
S (2s) & Mo (3d) overlap Cs (4s) 231 1.08 82.6
S (2p) overlaps Cs (4p) 167 3.83 86.8
Al (2p) overlaps Cs (4d) 78 5.25  

σ:  abbreviation for the term Scofield Photoionization Cross-Section which is used with IMFP and TF to produce an RSF for atom% quantitation

Plasmon Peaks

Energy Loss Peaks

Auger Peaks

Energy Loss    Intrinsic Plasmon Peak:  ~xx eV above peak max
Expected Bandgap for Cs2O:   0.6 – 1.6 eV  (https://materialsproject.org/)
Work Function for Cs:  xx eV

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

→  Periodic Table 

 

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

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

 

Cs (LMM) Auger Peaks from Cso Metal
 Fresh exposed bulk produced by extensive Ar+ ion etching
Cso Metal – high BE Auger range Cso Metal – low BE Auger range
 

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Evidence for Breakdown in One-Electron Orbital Concept
in Elements Z=46 (Palladium) to Z= 59 (Praseodymium)

Rhodium (4s) and (4p) Peakshapes Cesium (4s) and (4p) Peakshapes Praseodymium (4s) and (4p) Peakshapes
   

Reference:
G. Wendin, Breakdown of One-Electron Pictures in Photoelectron Spectra, Structure and Bonding Series #45, Springer-Verlag, New York, 1981

 
   

 

Side-by-Side Comparison of
Cesium Fluoride (CsF) & Cesium Iodide (CsI)
Peak-fits, BEs, FWHMs, and Peak Labels
Cesium Fluoride (CsF) Cesium Iodide (CsI)
Cs (3d) from CsF
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Cs (3d) from CsI
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
  .
Cesium Fluoride (CsF) Cesium Iodide (CsI)
C (1s) from CsF
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

C (1s) from CsI
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
 
→  Periodic Table 
  .
Cesium Fluoride (CsF) Cesium Iodide (CsI)
F (1s) from CsF
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

I (3d) from CsI
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
→  Periodic Table

 
 

 

Survey Spectrum of Cesium Fluoride, CsF
with Peaks Integrated, Assigned and Labelled

 

→  Periodic Table 

 

 

Survey Spectrum of Cesium Iodide, CsI
with Peaks Integrated, Assigned and Labelled

→  Periodic Table 

 

Overlays of Cs (3d) Spectra for
Cesium metal, CsF and CsI

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

 

 Overlay of Cso metal and CsF :   Cs (3d)
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
Chemical Shift:  –0.9 eV
  Overlay of Cso metal and CsI :   Cs (3d)
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
Chemical Shift:  –0.2 eV
→  Periodic Table  Copyright ©:  The XPS Library 

 

Overlay of Cs (3d)
Cso Metal, CsF, & CsI  

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Valence Band Spectra
CsF, CsI

CsF
Flood gun is ON,  Charge referenced so C (1s) = 285.0 eV		 CsI 
Flood gun is ON,  Charge referenced so C (1s) = 285.0 eV

Overlay of Valence Band Spectra
for Cs-F and Cs-I

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Peak-fits of Cesium Halides for Comparison – Cs (3d)
Cesium Fluoride, CsF, powder
Peak-fit of Cs (3d) from CsF
freshly cleaved in lab air
Charge Referenced to 285.0 eV		 Cesium Chloride, CsCl, single crystal, cleaved
Peak-fit of Cs (3d) from CsCl
freshly cleaved in lab air
Charge Referenced to 285.0 eV
Cesium Bromide, CsBr, crystallites crushed
Peak-fit of Cs (3d) from CsBr
freshly cleaved in lab air
Charge Referenced to 285.0 eV

Cesium Iodide, CsI, crystal scraped
Peak-fit of Cs (3d) from CsI
freshly cleaved in lab air
Charge Referenced to 285.0 eV

Overlay of Cs (3d5/2) Peak from:
Cso Metal, CsF, and CsI

Overlay of Cs (3d5/2) Peak from:
CsF, CsCl, CsBr, and CsI

 

Overlay of Cs (3d) Spectra from:
CsHCO3 and Cs2CO3
Cesium Carbonate, Cs2CO3
Peak-fit of Cs (3d) from Cs2CO3, powder
pressed onto stage
Charge Referenced to 285.0 eV		 Cesium Hydrogen Carbonate, CsHCO3
Peak-fit of Cs (3d) from CsHCO3, crystallites
freshly crushed
Charge Referenced to 285.0 eV
 
  .
Cesium Carbonate, Cs2CO3
Peak-fit of C (1s) from Cs2CO3, powder
pressed onto stage
Charge Referenced to 285.0 eV		 Cesium Hydrogen Carbonate, CsHCO3
Peak-fit of C (1s) from CsHCO3, crystallites
freshly crushed
Charge Referenced to 285.0 eV
Overlay of C (1s) Spectra
from CsHCO3 and Cs2CO3
 
Overlay of Cs (3d) Spectra
from CsHCO3 and Cs2CO3
 
Overlay of O (1s) Spectra
from CsHCO3 and Cs2CO3

Features Observed

  • xx
  • xx
  • xx

Cesium Minerals, Gemstones, and Chemical Compounds

 
Pollucite – Cs2(Al2Si4O12)-2H2O Cesiodymite – CsKCu5O(SO4)5 Pezzpttaite – Cs(Be2Li)Al2(Si6O18) Rhodizite – (Cs)Al4Be4(B,Be)12O28

→  Periodic Table 

 

 

Six (6) Chemical State Tables of Cs (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 (2p3/2) 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 (2p3/2) 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

Cs (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
Cs 55 Cs – element  (N*2) 726.0 eV 726.3 eV 285.0 eV The XPS Library
Cs 55 Cs2.5Te (N*3) 726.3 eV 726.4 eV 284.8 eV Avg BE – NIST
Cs 55 Cs-2O (N*2) 725.2 eV 726.1 eV 284.8 eV Avg BE – NIST
Cs 55 CsBr (N*2) 724.0 eV 724.1 eV 284.8 eV Avg BE – NIST
Cs 55 CsCl (N*2) 723.7 eV 724.0 eV 284.8 eV Avg BE – NIST
Cs 55 Cs-HCO3 723.8eV   285.0 eV The XPS Library
Cs 55 Cs2-CO3 725.2 eV   285.0 eV The XPS Library
Cs 55 CsF (N*1) 724.0 eV   284.8 eV Avg BE – NIST
Cs 55 CsI (N*1) 723.9 eV   284.8 eV Avg BE – NIST
Cs 55 CsOH (N*1) 724.2 eV   284.8 eV Avg BE – NIST
Cs 55 Cs-2SO4 724.4 eV   285.0 eV The XPS Library
Cs 55 Cs-Br 724.5 eV   285.0 eV The XPS Library
Cs 55 Cs-Cl 724.7 eV   285.0 eV The XPS Library
Cs 55 Cs-F 725.4 eV   285.0 eV The XPS Library
Cs 55 Cs-I 726.0 eV   285.0 eV The XPS Library

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 (2p3/2) 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

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

C (1s) BE = 284.8 eV

→  Periodic Table 

Copyright ©:  Ulvac-PHI

Table #3

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

C (1s) BE = 284.8 eV

Chemical state Binding energy (eV), Cs (3d5/2)
CsI 724

→  Periodic Table 

Copyright ©:  Thermo Scientific 

Table #4

Cs (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


No BE Table Available

→  Periodic Table 

Copyright ©:  Mark Beisinger

Table #5

Cs (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
Cs 3d5/2 CsN3 723.7 ±0.2 723.5 ～ 723.9
Cs 3d5/2 Halides 723.8 ±0.2 723.6 ～ 724.0
Cs 3d5/2 Cs2SO4 724.0 ±0.3 723.7 ～ 724.2
Cs 3d5/2 Cs3PO4 724.0 ±0.3 723.7 ～ 724.2
Cs 3d5/2 Cs4P2O7 724.0 ±0.3 723.7 ～ 724.2
Cs 3d5/2 CsCr2O7 724.1 ±0.3 723.8 ～ 724.3
Cs 3d5/2 CsClO4 724.3 ±0.3 724.0 ～ 724.5
Cs 3d5/2 CsOH 724.5 ±0.2 724.3 ～ 724.7
Cs 3d5/2 CsCrO4 724.6 ±0.3 724.3 ～ 724.8
Cs 3d5/2 Cs 726.1 ±0.3 725.8 ～ 726.3

 

→  Periodic Table 

 

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

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

 

Histogram indicates:  724.5 eV for CsOH based on 2 literature BEs Histogram indicates:  725.7 eV for Cs2O based on 2 literature BEs

Table #6


NIST Database of Cs (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
Cs 3d5/2 CsN3 723.60  Click
Cs 3d5/2 CsCl 723.70  Click
Cs 3d5/2 Cs4P2O7 723.80  Click
Cs 3d5/2 CsI 723.90  Click
Cs 3d5/2 CsI 723.90  Click
Cs 3d5/2 Cs3PO4 723.90  Click
Cs 3d5/2 Cs2SO4 723.90  Click
Cs 3d5/2 Cs2Cr2O7 723.90  Click
Cs 3d5/2 CsBr 724.00  Click
Cs 3d5/2 CsCl 724.00  Click
Cs 3d5/2 CsF 724.00  Click
Cs 3d5/2 CsBr 724.10  Click
Cs 3d5/2 CsOH 724.15  Click
Cs 3d5/2 Cs2[Rh2Br2(HCOO)4] 724.20  Click
Cs 3d5/2 CsClO4 724.20  Click
Cs 3d5/2 Cs2[Rh2Br(HCOO)4(NO2)] 724.30  Click
Cs 3d5/2 Cs2[Rh2Cl2(HCOO)4] 724.40  Click
Cs 3d5/2 Cs2CrO4 724.50  Click
Cs 3d5/2 Cs0.78Te 724.57  Click
Cs 3d5/2 Cs0.90Te 724.62  Click
Cs 3d5/2 CsOH/Cu 724.80  Click
Cs 3d5/2 Cs/Te 725.01  Click
Cs 3d5/2 Cs2O 725.10  Click
Cs 3d5/2 Cs2O 725.20  Click
Cs 3d5/2 Cs/Cu 725.40  Click
Cs 3d5/2 Cs/Cu 725.70  Click
Cs 3d5/2 Cs 726.00  Click
Cs 3d5/2 Cs/Cu 726.00  Click
Cs 3d5/2 Rb7[Cs11O3] 726.10  Click
Cs 3d5/2 Cs10[Cs11O3] 726.20  Click
Cs 3d5/2 Cs2.69Te 726.28  Click
Cs 3d5/2 Cs 726.30  Click
Cs 3d5/2 Cs2.6Te 726.33  Click
Cs 3d5/2 Cs2.4Te 726.36  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 Cesium Materials

 

 

 

Expert Knowledge Explanations

 

→  Periodic Table 

 

Cesium Chemical Compounds

Peak-fits and Overlays of Chemical State Spectra

Pure Cesium, Cso:  Cs (3d5/2)
Cu (2p3/2) BE = 932.6 eV		 Cs2CO3:  Cs (3d)
C (1s) BE = 285.0 eV		 CsF:  Cs (3d)
C (1s) BE = 285.0 eV

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Overlay of Cs (3d) Spectra shown Above

C (1s) BE = 285.0 eV

 

Chemical Shift between Cs and Cs2CO3:  xxx eV
 Chemical Shift between Cs and CsF:  xxxeV

 

→  Periodic Table 

 

Cesium Sulfate, (Cs2SO4)
pressed pellet

Survey Spectrum from Cs2SO4
Flood gun is ON, C (1s) BE = 285.0 eV
 Cs (3d) Chemical State Spectrum from Cs2SO4
Flood gun is ON, C (1s) BE = 285.0 eV
  . 
O (1s) Chemical State Spectrum from Cs2SO4
Flood gun is ON, C (1s) BE = 285.0 eV
 C (1s) Chemical State Spectrum from Cs2SO4
Flood gun is ON, C (1s) BE = 285.0 eV
  . 
Valence Band Spectrum from Cs2SO4
Flood gun is ON, C (1s) BE = 285.0 eV
 S (2p) Chemical State Spectrum from Cs2SO4
Flood gun is ON, C (1s) BE = 285.0 eV


Shake-up Features for Cs2O

   
   

 

 

Multiplet Splitting Features for Metal Compounds

Cs metal – Splitting Cs2O  – Multiplet Splitting Peaks
   

 

 

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

 

Cesium Chemical Compounds

 

Cesium Fluoride, CsF

Survey Spectrum Cs (3d) Spectrum
  .
C (1s) Spectrum F (1s) Spectrum
  .
Valence Band Spectrum  
 
   
   

→  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 Cesium – CsX

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 

Copyright ©:  The XPS Library
 

 

Cesium Alloys

   
XxCu XxCu
→  Periodic Table   
XxCu XxCu

 

Copyright ©:  The XPS Library 

 

 

 

XPS Facts, Guidance & Information

→  Periodic Table 

    Element   Cesium (Cs)
  
    Primary XPS peak used for Peak-fitting:   Cs (3d5/2)  
    Spin-Orbit (S-O) splitting for Primary Peak:   Spin-Orbit splitting for “d” Orbital, ΔBE = 13.9 eV
  
    Binding Energy (BE) of Primary XPS Signal:   725 eV
  
    Scofield Cross-Section (σ) Value:   Cs (3d5/2) = 23.76.     Cs (3d3/2) = 16.46
  
    Conductivity:   Cs resistivity =  
Native Oxide suffers Differential Charing		  
    Range of Cs (3d5/2) Chemical State BEs:   725 – 730 eV range   (Cso to CsF)  
    Signals from other elements that overlap
Cs (3d5/2) Primary Peak:		   xxx  
    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 

  

Copyright ©:  The XPS Library 

→  Periodic Table 

 

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

  • FWHM (eV) of Cs (3d5/2) for Pure Cso :  ~1.3 eV using 25 eV Pass Energy after ion etching:
  • FWHM (eV) of Cs (3d5/2) for Cs2CO3:  ~2.5 eV using 50 eV Pass Energy  (before ion etching)
  • Binding Energy (BE) of Primary Signal used for Measuring Chemical State Spectra:  725 eV for Cs (3d5/2) with +/- 0.2 uncertainty
  • List of XPS Peaks that can Overlap Peak-fit results for Cs (3d5/2):  xxx

→  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) = ~0.90 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
    • Ag (3d5/2) FWHM (eV) = ~0.85 eV for PE 50 on SSI S-Probe
  • 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.
  • Constraints used on Peak-fitting: typically constrain the peak area ratios based on the Scofield cross-section values
  • Asymmetry for Conductive materials:  20-30% with increased Lorentzian %
  • Peak-fitting “2s” or “3s” Peaks:  Often need to use 50-60% Lorentzian peak-shape

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 Cesium

  • Cesium develops a thick native oxide due to the reactive nature of clean Cesium .
  • The native oxide of Cs Ox is 8-9 nm thick.
  • Cesium thin films often have a low level of iron (Fe) in the bulk as a contaminant or to strengthen the thin film
  • Cesium 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 Cs (3d)  
  • 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 Cesium (Cs)

  • Conductivity:  Metal 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:  Cs (3d5/2) at 725 eV
  • Recommended Pass Energy for Measuring Chemical State Spectrum: 50-60 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:  700- 750 eV
  • Recommended Extended BE Range for Measuring Chemical State Spectrum:  700 – 800 eV
  • Recommended BE Range for Survey Spectrum:  -10 to 1,100 eV   (above 1,100 eV there are no useful XPS signals, except for Ge, As and Ga, above 1100 is waste of time)
  • 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 Cs 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
 
 
from Thermo website
 
 
 

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