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

 

Xenon (Xe)

 

 Xenon Tetra-Fluoride – XeF4  Xenon (Xeo) Gas in Discharge Tube Xenon Di-fluoride – XeF2

 


Visible Emission Spectrum (400-700 nm, 3.1 eV – 1.8 eV) from Xenon Gas

 


Xenon (Xe+) Implanted into HOPG

Peak-fits, BEs, FWHMs, and Peak Labels

Xenon (Xe+) Implanted
Xe (3d) Spectrum – raw spectrum
as implanted by ion etching with Xe+		 Xenon (Xe+) Implanted
Peak-fit of Xe (3d) Spectrum (w/o asymm)
  .
 Xe (3d) energy loss peak – ~30 eV from peak  Xe (3d) loss shoulder

. 
Xenon (Xe+) Implanted
Xe (4d) Spectrum – raw spectrum
as implanted by ion etching with Xe+		 Xenon (Xe+) Implanted
Xe (4d) Spectrum – peak-fit
as implanted by ion etching with Xe+

. 
Xenon (Xe+) Implanted
Xe (4s, 4p) Spectrum – raw spectrum
1 electron Breakdown present
as implanted by ion etching with Xe+		 Xenon (Xe+) Implanted
Xe (4s, 4p) Spectrum – labelled
as implanted by ion etching with Xe+
 

Survey Spectrum of Xenon (Xe+) Implanted into Graphite

with Peaks Integrated, Assigned and Labelled

 

 

XPS Signals for Xenon , (Xe)

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
Xe (3p1/2) 995 5.20 15.9
Cu (2p) Xe (3p3/2)  934  10.99 15.9
Xe (3d3/2)  682.13  15.10  21.2
Xe (3d5/2)  669.48  21.79  21.2
Xe (4s)  206  1.02  30.2
P (2p) Xe (4p) 139 3.58 31.4
Na (2s) Xe (4d) 61 4.68

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

Energy Loss Peak

~30 eV above peak max

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

→  Periodic Table 

 

Six (6) Chemical State Tables of Xe (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

Xe (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
Xe 57 Xe implanted in graphite 669.5 eV 285.0 eV The XPS Library
Xe 57 Xe/Ni 669.4 eV 670.7 eV 284.8 eV NIST database

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 (3d7/2) 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

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

C (1s) BE = 284.8 eV

 

→  Periodic Table 

Copyright ©:  Ulvac-PHI

Table #3

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

C (1s) BE = 284.8 eV

Chemical state Binding energy (eV), Xe (3d5/2)
Implanted Xe 670

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Copyright ©:  Thermo Scientific 

Table #4

Xe (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 Xeisinger

Table #5

Xe (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
Xe 3d5/2 Xe in Au 669.0 ±0.3 668.7 ～ 669.2
Xe 3d5/2 Xe in Ag 669.6 ±0.2 669.4 ～ 669.8
Xe 3d5/2 Xe in Cu 669.6 ±0.2 669.4 ～ 669.8
Xe 3d5/2 Xe in graphite 669.6 ±0.2 669.4 ～ 669.8
Xe 3d5/2 Xe in Fe 670.3 ±0.3 670.0 ～ 670.5
Xe 3d5/2 Na4XeO6 674.0 ±0.2 673.8 ～ 674.2

 

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

 

Histogram indicates:  669.8 eV for Xeo based on 7literature BEs  
na

Table #6


NIST Database of Xe (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.

 

Element Spectral Line Formula Energy (eV) Reference
Xe 3d5/2 Xe 668.90  Click
Xe 3d5/2 Xe/Ni 669.40  Click
Xe 3d5/2 Xe 669.60  Click
Xe 3d5/2 Xe 669.60  Click
Xe 3d5/2 Xe 669.65  Click
Xe 3d5/2 Xe 669.80  Click
Xe 3d5/2 Xe 670.20  Click
Xe 3d5/2 Xe 670.70  Click
Xe 3d5/2 Na4XeO6 674.10  Click

 

 

Statistical Analysis of Binding Energies in NIST XPS Database of BEs

 

 

→  Periodic Table 

 

 

XPS Facts, Guidance & Information

→  Periodic Table 

    Element Xenon (Xe)
  
    Primary XPS peak used for Peak-fitting: Xe (3d5/2)  
    Spin-Orbit (S-O) splitting for Primary Peak: Spin-Orbit splitting for “d” Orbital, ΔBE = 12.8 eV
  
    Binding Energy (BE) of Primary XPS Signal: 669.5  eV
  
    Scofield Cross-Section (σ) Value: Xe (3d5/2) = 21.79
  
    Conductivity:  
    Range of Xe (3d5/2) Chemical State BEs:  668 – 670 eV range    
Signals from other elements that overlap
Xe (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 

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

 

  • FWHM (eV) of Xe (3d5/2) for Pure Xeo :  ~1.1 eV using 25 eV Pass Energy after ion etching:
  • Binding Energy (BE) of Primary Signal used for Measuring Chemical State Spectra:  xx eV for Xe (3d5/2) with +/- 0.2 uncertainty
  • List of XPS Peaks that can Overlap Peak-fit results for Xe (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.

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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

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Data Collection Guidance

 

  • Chemical state differentiation can be difficult
  • Collect principal Xe (3d5/2) peak
  • 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

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Data Collection Settings for Xenon (Xe)

 

  • 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:  Xe (3d5/2) at 669 eV
  • Recommended Pass Energy for Measuring Chemical State Spectrum: 25-40 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:  660 – 700 eV
  • Recommended Extended BE Range for Measuring Chemical State Spectrum:  650 – 750 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 

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Effects of Argon Ion Etching

 

  • Carbides appear after ion etching Xe 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

 

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Copyright ©:  The XPS Library 
Gas Phase XPS or UPS Spectra

 

Chemical State Spectra from Literature

End of File