Bao BaO BaCO3 BaSO4 BaF2 BaTiO3 BaZrO3 Glass 7059 BaHfF6 BaMoO4 YBaCuOx   

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

 

Barium (Ba)

 

Baryte – BaSO4 Oxidized Barium Metal – Bao Benitoite – BaTiSi3O9

 

  Page Index
  • Expert Knowledge & Explanations


Barium (Bao) Metal
Peak-fits, BEs, FWHMs, and Peak Labels

Barium (Bao) Metal
Ba (3d) Spectrum – raw spectrum		 Barium (Bao) Metal
Peak-fit of Ba (3d5/2) Spectrum (w/o asymm)
→  Periodic Table – HomePage  
Barium (Bao) Metal
Ba (3d) Spectrum – extended range 
 Barium (Bao) Metal
Peak-fit of Ba (3d5/2) Spectrum (w asymm)
   

 

Survey Spectrum of Barium (Bao) Metal
with Peaks Integrated, Assigned and Labelled

→  Periodic Table 

XPS Signals for Barium, (Bao) 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
  Ba (3p1/2) 1137 5.42 21.6
  Ba (3p3/2) 1063 11.71 21.6
  Ba (3d3/2) 796 17.92 31.5
  Ba (3d5/2) 781 25.84 31.5
Rb (3p) overlaps Ba (4s) 253 1.13 48.8
Zr (3d) overlaps Ba (4p3/2) 180 2.73 51.1
Mg (2s) overlaps Ba (4d) 92 5.76  

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

Plasmon Peaks

Energy Loss Peaks

Auger Peaks

Energy Loss    Intrinsic Plasmon Peak:  ~xx eV above peak max
Expected Bandgap for BaO:  2.0 – 2.7 eV   (https://materialsproject.org/)
Work Function for Ba:  xx eV

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

→  Periodic Table 

 

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

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

 

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

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Evidence for Breakdown in One-Electron Orbital Concept
in Elements Z=45 (Rhodium) to Z= 59 (Praseodymium)

Rhodium (4s) and (4p) Peakshapes Barium (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

Barium Oxide (BaO) & Barium Carbonate (BaCO3)
Peak-fits, BEs, FWHMs, and Peak Labels
BaO  (contaminated w BaCO3) BaCO3
Ba (3d) from BaO
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Ba (3d) from BaCO3
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
  .
BaO BaCO3
C (1s) from BaO
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

C (1s) from BaCO3
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
→  Periodic Table 
  .
BaO BaCO3
O (1s) from BaO
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV

O (1s) from BaCO3
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
→  Periodic Table

 
 

Survey Spectrum of Barium Oxide, BaO
(contaminated with BaCO3)
with Peaks Integrated, Assigned and Labelled

 

→  Periodic Table 

 

 

Survey Spectrum of Barium Carbonate, BaCO3
with Peaks Integrated, Assigned and Labelled

→  Periodic Table  

 

Overlays of Ba (3d5/2) Spectra for:
Barium metal, BaO and BaCO3

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

 Overlay of Bao metal and BaO  – Ba (3d5/2)
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
Chemical Shift:  -0.2 eV
  Overlay of Bao metal and BaCO3 – Ba (3d5/2)
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
Chemical Shift:  -0.8 eV
→  Periodic Table  Copyright ©:  The XPS Library 

 

Overlay of Ba (3d5/2)
Bao Metal, BaO, & BaCO3   

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Valence Band Spectra
BaO, BaCO3

BaO (contam w BaCO3)
Flood gun is ON,  Charge referenced so C (1s) = 285.0 eV		 BaCO3
Flood gun is ON,  Charge referenced so C (1s) = 285.0 eV

Overlay of Valence Band Spectra
for BaO and BaCO3

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Peak-fits of Ba (3d5/2)
Bao, BaO, Barium Fluoride, Barium Sulfate 
Pure Metal, Bao Barium Oxide, BaO
Ba (3d) from Barium metal – peak-fit
Ion Etched
 Peak-fit of Ba (3d) from BaO
Charge Referenced to 285.0 eV

  , 
Barium Fluoride, BaF2
Peak-fit of Ba (3d) from BaF2
powder
Charge Referenced to 285.0 eV		 Barium Sulfate, BaSO4, natural crystal
Peak-fit of Ba (3d) from BaSO4, natural crystal
freshly cleaved in lab air
Charge Referenced to 285.0 eV

Overlay of Ba (3d5/2)
Peak from Bao, BaO, BaSO4, and BaF2

 

 

Features Observed

  • xx
  • xx
  • xx

Barium Minerals, Gemstones, and Chemical Compounds

 
Barium Permanganate – Ba(MnO4)2 Witherite – BaCO3 Barium Carbonate – BaCO3 Barium Chromate – Ba(CrO4)2

→  Periodic Table 

 

 

Six (6) Chemical State Tables of Ba (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

Ba (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
Ba 56 YBaCuOx 778.3 eV    285.0 eV The XPS Library
Ba 56 Ba – element  (N*4) 779.3 eV 780.7 eV  284.8 eV Avg BE – NIST
Ba 56 Ba-O (N*4) 779.4 eV 779.9 eV  284.8 eV Avg BE – NIST
Ba 56 Ba-OAc 779.5 eV    285.0 eV The XPS Library
Ba 56 Ba-CO3 779.8  eV    285.0 eV The XPS Library
Ba 56 Ba-CO3 (N*2) 779.8 eV 779.9 eV  284.8 eV Avg BE – NIST
Ba 56 Ba-F2 (N*2) 779.8 eV 781.7 eV  284.8 eV Avg BE – NIST
Ba 56 Ba-S (N*1) 779.8 eV    284.8 eV Avg BE – NIST
Ba 56 Ba-F2 780.4  eV    285.0 eV The XPS Library
Ba 56 Ba-O 780.2  eV    285.0 eV The XPS Library
Ba 56 Ba-SO4 780.7  eV    285.0 eV The XPS Library
Ba 56 Ba-O2 (N*1) 780.8 eV    284.8 eV Avg BE – NIST
Ba 56 Ba-(ClO4)2 (N*1) 780.9 eV    284.8 eV Avg BE – NIST
Ba 56 Ba-H2 (N*1) 782.9 eV    284.8 eV Avg BE – NIST
Ba 56 Ba-(OH)2      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 (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

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

C (1s) BE = 284.8 eV

→  Periodic Table 

Copyright ©:  Ulvac-PHI

Table #3

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

C (1s) BE = 284.8 eV

Chemical state Binding energy (eV), Ba (3d5/2)
BaCO3/BaO 780.0
BaSO4 780.1

→  Periodic Table 

Copyright ©:  Thermo Scientific 

Table #4

Ba (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

Ba (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
Ba 3d5/2 BaCrO4 779.0 ±0.3 778.7 ～ 779.2
Ba 3d5/2 BaMoO4 779.1 ±0.3 778.8 ～ 779.3
Ba 3d5/2 BaO 779.5 ±0.4 779.1 ～ 779.9
Ba 3d5/2 BaRh2O4 779.6 ±0.3 779.3 ～ 779.8
Ba 3d5/2 BaS 779.9 ±0.3 779.6 ～ 780.1
Ba 3d5/2 BaCO3 780.0 ±0.3 779.7 ～ 780.2
Ba 3d5/2 Ba 780.4 ±0.3 780.1 ～ 780.6
Ba 3d5/2 BaSO4 780.4 ±0.5 779.9 ～ 780.8
Ba 3d5/2 Ba(NO3)2 780.8 ±0.3 780.5 ～ 781.0

→  Periodic Table 

 

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

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

Histogram indicates:  780.1 eV for Bao based on 4 literature BEs Histogram indicates:  779.6 eV for BaO based on 5 literature BEs

Table #6


NIST Database of Ba (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
Ba 3d5/2 YBa2Cu3O7 778.10  Click
Ba 3d5/2 BaCrO4 778.90  Click
Ba 3d5/2 BaMoO4 779.10  Click
Ba 3d5/2 BaO 779.10  Click
Ba 3d5/2 Ba 779.30  Click
Ba 3d5/2 BaO 779.40  Click
Ba 3d5/2 BaRh2O4 779.60  Click
Ba 3d5/2 BaO 779.60  Click
Ba 3d5/2 Ba 779.80  Click
Ba 3d5/2 BaCO3 779.80  Click
Ba 3d5/2 BaF2 779.80  Click
Ba 3d5/2 BaS 779.80  Click
Ba 3d5/2 BaO 779.85  Click
Ba 3d5/2 BaCO3 779.90  Click
Ba 3d5/2 BaSO4 779.90  Click
Ba 3d5/2 BaO 779.90  Click
Ba 3d5/2 Ba/O2/Ni 780.10  Click
Ba 3d5/2 Ba(ClO3).H2O 780.20  Click
Ba 3d5/2 Ba(NO3)2 780.30  Click
Ba 3d5/2 Ba/O2 780.37  Click
Ba 3d5/2 BaSO4 780.40  Click
Ba 3d5/2 Ba 780.60  Click
Ba 3d5/2 Ba(NO3)2 780.70  Click
Ba 3d5/2 BaSO4 780.70  Click
Ba 3d5/2 Ba 780.72  Click
Ba 3d5/2 BaSO4 780.80  Click
Ba 3d5/2 BaO2 780.80  Click
Ba 3d5/2 Ba(ClO4)2 780.90  Click
Ba 3d5/2 Ba/Ca/Cd/Sr/in_montmorillonite 781.20  Click
Ba 3d5/2 BaCl2.2H2O 781.60  Click
Ba 3d5/2 BaF2 781.70  Click
Ba 3d5/2 BaH2 782.90  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 Barium Materials

 

 

 

Expert Knowledge Explanations

 

→  Periodic Table 

 

Barium Chemical Compounds

 

Peak-fits and Overlays of Chemical State Spectra

Pure Barium, Bao:  Ba (3d)
Cu (2p3/2) BE = 932.6 eV		 BaCO3:  Ba (3d)
C (1s) BE = 285.0 eV		 BaF2: Ba (3d)
C (1s) BE = 285.0 eV

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Overlay of Ba (3d5/2) Spectra shown Above

C (1s) BE = 285.0 eV

 

→  Periodic Table 


Shake-up Features for
BaO and BaSO4

BaO BaSO4

 

 

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

 

 

Barium Chemical Compounds

 

Barium Sulfate, BaSO4

Survey Spectrum Ba (3d5/2) Spectrum
  .
C (1s) Spectrum O (1s) Spectrum
  .
Valence Band Spectrum S (2p) Spectrum
   
   

Barium Fluoride, BaF2

Survey Spectrum Ba (3d5/2) Spectrum
  . 
C (1s) Spectrum F (1s) Spectrum
  .
Valence Band Spectrum Ba (4d) Spectrum
   
   

 

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 Barium

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 

 

Barium Alloys

   
XxCu XxCu
→  Periodic Table   
XxCu XxCu

 

Copyright ©:  The XPS Library 

 

 

XPS Facts, Guidance & Information

→  Periodic Table 

    Element   Barium (Ba)
  
    Primary XPS peak used for Peak-fitting:   Ba (3d5/2)  
    Spin-Orbit (S-O) splitting for Primary Peak:   Spin-Orbit splitting for “d” Orbital, ΔBE = 15.3 eV
  
    Binding Energy (BE) of Primary XPS Signal:   780.5 eV
  
    Scofield Cross-Section (σ) Value:   Ba (3d5/2) = 25.84.       Ba (3d3/2) = 17.92
  
    Conductivity:   Ba resistivity =  
Native Oxide suffers Differential Charing		  
    Range of Ba (3d5/2) Chemical State BEs:   779 – 793 eV range   (Bao to BaF2)  
    Signals from other elements that overlap
Ba (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 Ba (3d5/2)

  • FWHM (eV) of Ba (3d5/2) for Pure Bao :  ~1.2 eV using 25 eV Pass Energy after ion etching:
  • FWHM (eV) of Ba (3d5/2) for BaO:  ~2.0 eV using 50 eV Pass Energy  (before ion etching)
  • Binding Energy (BE) of Primary Signal used for Measuring Chemical State Spectra:  780 eV for Ba (3d5/2) with +/- 0.2 uncertainty
  • List of XPS Peaks that can Overlap Peak-fit results for Ba (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 Barium

  • Barium develops a very thick native oxide due to the reactive nature of clean Metal.
  • The native oxide of Ba Ox is 8-9 nm thick.
  • Barium thin films often have a low level of iron (Fe) in the bulk as a contaminant or to strengthen the thin film
  • Barium 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 Ba (3d5/2) peak as well as Ba (4d5/2).
  • 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 Barium (Ba)

  • Conductivity:  Barium 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:  Ba (3d5/2) at 780 eV
  • Recommended Pass Energy for Measuring Chemical State Spectrum: 50-90 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:  760- 820eV
  • Recommended Extended BE Range for Measuring Chemical State Spectrum:  750 – 850 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 Ba 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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