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

 

Oxygen (O)

 

Diaspore  –  α-AlO(OH) Sapphire  –  Al2O3 Goethite  –  α-FeO(OH)

 

  Page Index
  • Peak-fits and Overlays of O Chemical Compounds
  • Expert Knowledge & Explanations


Oxygen (O)


α-AlO(OH), Diaspore
natural crystal, exposed bulk
Peak-fits, BEs, FWHMs, and Peak Labels

 


α-AlO(OH), Diaspore
O (1s) Spectrum – raw
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV
α-AlO(OH), Diaspore
O (1s) Spectrum – raw peak-fit
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV

  .

α-AlO(OH), Diaspore
Al (2p) spectrum – raw
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV
α-AlO(OH), Diaspore
 Al (2p) spectrum – peak-fit
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV

 .
α-AlO(OH), Diaspore
Al (2s) spectrum – raw
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV		 α-AlO(OH), Diaspore
Al (2s) spectrum – peak-fit
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV
  .
α-AlO(OH), Diaspore
Valence Band spectrum
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV
 α-AlO(OH), Diaspore
C (1s) spectrum
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV
 

 

Survey Spectrum of Aluminum Oxyhydroxide
α-AlO(OH) (Diaspore)

with Peaks Integrated, Assigned and Labelled

→  Periodic Table 

XPS Signals for Oxygen, (O)

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
Sb (3d), Na (Auger) & Pd (3d) overlap O (1s) 530 2.93 26.7
  O (2s) 24 0.1405 37.5
  O (2p) 8 0.0193 37.8

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

Expected Bandgaps
Expected Bandgap for BeO:  7 – 7.5 eV   (https://materialsproject.org)
Expected Bandgap for B2O3:  6-8 eV
Expected Bandgap for MgO:  3-4 eV
Expected Bandgap for Al2O3: 4-6 eV
Expected Bandgap for SiO2:  5-6 eV
*Scofield Cross-Section (σ) for C (1s) = 1.0


Features Observed

  • xx
  • xx

→  Periodic Table 

 

Side-by-Side Comparison of:
Oxygen Bearing Compounds

Metal Oxides, Hydroxides, Carbonates, & Sulfates of
Fe, Cu, Pb, Al, Mg, K, and Hg
Peak-fits, BEs, FWHMs, and Overlays
     .
α-Fe2O3, Hematite, crystal
O 1s spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
 α-FeO(OH), Goethite, crystal
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of O (1s) Spectra 
from α-FeOOH and α-Fe2O3
    . 
Cu2O, Cuprite, man-made crystal
O(1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 CuO, powder
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of O (1s) Spectra 
from Cu2O and CuO
     .
PbO, powder
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 PbCO3, Cerrusite, crystal
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of O (1s) Spectra 
from PbO and PbCO3
     .
Al2O3, Sapphire, man-made crystal
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 α-AlO(OH), Diaspore, crystal
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of O (1s) Spectra 
from α-AlO(OH) and Al2O3
     
     .
Al2O3, Sapphire, man-made crystal
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Al(OH)3, powder
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of O (1s) Spectra 
from Al(OH)3 and Al2O3
     .
MgO, man-made crystal
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 MgCO3, Magnesite, crystal
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of O (1s) Spectra 
from MgO and MgCO3
    .
MgO, man-made crystal
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 MgSO4, anhydrous powder
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of O (1s) Spectra 
from MgO and MgSO4
     
     .
K2CO3, (carbonate) crystallites
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 KHCO3, (bi-carbonate) crystallites
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of O (1s) Spectra 
from K2CO3 and KHCO3
Overlay of Valence Band Spectra
K2CO3 and KHCO3		 Overlay of C (1s) Spectra – expanded
K2CO3 and KHCO3
 Overlay of C (1s) spectra
K2CO3 and KHCO3
     .
HgO powder
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Hg2SO4 powder
O (1s) spectrum
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV		 Overlay of O (1s) Spectra 
from HgO and Hg2SO4
     

 

 

 

Copper Nitrate

Cu(2+)   NO3(-)

Peak-fits, BEs, FWHMs, and Peak Labels

Cu(NO3)2 – 2H2O
O (1s) Spectrum – raw
freshly cleaved
charge referenced so C (1s) = 285.0 eV		 Cu(NO3)2 – 2H2O
O (1s) Spectrum – peak-fit
freshly cleaved
charge referenced so C (1s) = 285.0 eV
  .
Cu(NO3)2 – 2H2O
Cu (2p) Spectrum – raw
freshly cleaved
charge referenced so C (1s) = 285.0 eV		 Cu(NO3)2 – 2H2O
Cu (2p) Spectrum – peak-fit
freshly cleaved
charge referenced so C (1s) = 285.0 eV
  .
Cu(NO3)2 – 2H2O
N (1s) Spectrum – raw
freshly cleaved
charge referenced so C (1s) = 285.0 eV		 Cu(NO3)2 – 2H2O
N (1s) Spectrum – peak-fit
freshly cleaved
charge referenced so C (1s) = 285.0 eV
  . 
Cu(NO3)2 – 2H2O
Valence Band Spectrum – peak-fit
freshly cleaved
charge referenced so C (1s) = 285.0 eV		 Cu(NO3)2 – 2H2O
C (1s) Spectrum – peak-fit
freshly cleaved
charge referenced so C (1s) = 285.0 eV

 

Survey Spectrum of Copper Nitrate, Cu(NO3)2-2H2O
with Peaks Integrated, Assigned and Labelled

 


Potassium Di-hydrogen Phosphate
KH2PO4, man-made crystal

PO4(-)

Peak-fits, BEs, FWHMs, and Peak Labels

KH2PO4 crystal
O (1s) Spectrum – raw
pressed powder
charge referenced so C (1s) = 285.0 eV		 KH2PO4 crystal
O (1s) Spectrum – peak-fit
pressed powder
charge referenced so C (1s) = 285.0 eV
  .
KH2PO4 crystal
P (2p) Spectrum – raw
pressed powder
charge referenced so C (1s) = 285.0 eV		 KH2PO4 crystal
P (2p) Spectrum – peak-fit
pressed powder
charge referenced so C (1s) = 285.0 eV
   
KH2PO4 crystal
K (2p) Spectrum – raw
pressed powder
charge referenced so C (1s) = 285.0 eV		 KH2PO4 crystal
K (2p) Spectrum – peak-fit
pressed powder
charge referenced so C (1s) = 285.0 eV
  .
KH2PO4 crystal
Valence Band Spectrum
pressed powder
charge referenced so C (1s) = 285.0 eV		 KH2PO4 crystal
C (1s) Spectrum – peak-fit
pressed powder
charge referenced so C (1s) = 285.0 eV

 

Survey Spectrum of Potassium di-Hydrogen Phosphate, KH2PO4
with Peaks Integrated, Assigned and Labelled
Copyright ©:  The XPS Library

 

Oxygen (O) in Silicon Di-oxide, SiO2
(Natural Quartz Crystal)

Peak-fits, BEs, FWHMs, and Peak Labels

 SiO2 natural crystal
O (1s) Spectrum – raw
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV		 SiO2 natural crystal
O (1s) Spectrum – peak-fit
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV
  .
SiO2 natural crystal
Si (2p) Spectrum – raw
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV		 SiO2 natural crystal
Si (2p) Spectrum – peak-fit
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV
  .
SiO2 natural crystal
Si (2s) Spectrum – peak-fit
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV		 SiO2 natural crystal
C (1s) Spectrum – peak-fit
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV
  . 
SiO2 natural crystal
O (KLL) Auger Signal Spectrum of SiO2
freshly exposed bulk
charge referenced so C (1s) = 285.0 e		 SiO2 natural crystal
Valence Band Spectrum of SiO2
freshly exposed bulk
charge referenced so C (1s) = 285.0 eV

 

 

Survey Spectrum of Silicon Di-oxide, SiO2
with Peaks Integrated, Assigned and Labelled

→  Periodic Table 


Oxygen-based Minerals, Crystals, and Chemical Compounds
Gibbsite – Al(OH)3 Molybdite – MoO3 Tenorite – CuO Tellurite – TeO2

 


Six (6) Chemical State Tables of O (1s) BEs

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

 

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

O (1s) 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
O 8 O – element     285.0 eV The XPS Library
O 8 YBaCuOx 528.3 eV   285.0 eV The XPS Library
O 8 SrTiO3 529.5 eV   285.0 eV The XPS Library
O 8 M-OAc (N*5) 530.5 eV 531.5 eV   Avg BE – NIST
O 8 O-CO2-mtl 530.8 eV 531.8 eV 285.0 eV The XPS Library
O 8 O-H-mtl 530.8 eV 531.5 eV 285.0 eV The XPS Library
O 8 M-(OH)x (N*16) 530.9 eV 531.5 eV   Avg BE – NIST
O 8 O-C-O 531.1 eV   285.0 eV The XPS Library
O 8 O-CO2-mtl  (N*8) 531.1 eV 531.5 eV   Avg BE – NIST
O 8 O=C-N 531.5 eV 532.0 eV 285.0 eV The XPS Library
O 8 OH-Al 531.5 eV 532.0 eV 285.0 eV The XPS Library
O 8 O-SO 531.5 eV 531.8 eV 285.0 eV The XPS Library
O 8 O=C 531.6 eV 532.4 eV 285.0 eV The XPS Library
O 8 KOH (N*1) 531.7 eV     Avg BE – NIST
O 8 O-Si org 532.0 eV   285.0 eV The XPS Library
O 8 M-SO4 532.2 eV 533.1 eV 285.0 eV The XPS Library
O 8 O-SiO xtl 532.4 eV 532.8 eV 285.0 eV The XPS Library
O 8 O-C,O-H 532.5 eV 533.4 eV 285.0 eV The XPS Library
O 8 O-NO 532.5 eV   285.0 eV The XPS Library
O 8 M-NO3 (N*9) 532.7 eV 533.8 eV   Avg BE – NIST
O 8 NaOH (N*1) 532.8 eV     Avg BE – NIST
O 8 O-SiO 532.8 eV 533.8 eV 285.0 eV The XPS Library
O 8 H2O (N*5) 533.1 eV 535.1 eV   Avg BE – NIST
O 8 (CH3CH2)2O 533.4 eV   285.0 eV The XPS Library
O 8 O=CO2 org 533.6 eV 534.0 eV 285.0 eV The XPS Library
O 8 O ads.H2O 534.0 eV 535.0 eV 285.0 eV The XPS Library

Charge Referencing

  • (N*number) identifies the number of NIST BEs that were averaged to produce the BE in the middle column.
  • Binding Energy Scale calibration expects 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

O (1s) Chemical State BEs from:  “PHI Handbook”

C (1s) BE = 284.8 eV

 

→  Periodic Table 

Copyright ©:  Ulvac-PHI

Table #3

O (1s) Chemical State BEs from:  “Thermo-Scientific” Website

C (1s) BE = 284.8 eV

Chemical state Binding energy O (1s) / eV
Metal oxides 529–530
Metal carbonates 531.5–532
Al2O3 (alumina) 531.1
SiO2 532.9
Organic C-O 531.5–532
Organic C=O ~533
O-Fx ~535

→  Periodic Table 

Copyright ©:  Thermo Scientific 

Table #4

O (1s) 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

O (1s) 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
O 1s Metal Oxides 529.6 ±1.5 528.1 ～ 531.1
O 1s Fe2O3 529.9 ±0.3 529.6 ～ 530.2
O 1s Al2O3 530.9 ±1.0 529.9 ～ 531.8
O 1s Carbonates 531.0 ±0.5 530.5 ～ 531.5
O 1s Hydroxides 531.5 ±0.6 530.9 ～ 532.0
O 1s Phosphates 531.6 ±1.2 530.4 ～ 532.8
O 1s Sulfates 532.0 ±0.5 531.5 ～ 532.5
O 1s Silicones 532.7 ±0.2 532.5 ～ 532.8
O 1s Chlorates 532.8 ±0.2 532.6 ～ 533.0
O 1s SiO2 532.9 ±0.4 532.5 ～ 533.3
O 1s Nitrates 533.2 ±0.6 532.6 ～ 533.7

→  Periodic Table 

 

 

Histograms of NIST BEs for O (1s) BEs

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

Histogram indicates:  529.6 eV for NiO based on 13 literature BEs Histogram indicates:  529.8 eV for CuO based on 12 literature BEs

Histogram indicates:  529.9 eV for Fe2O3 based on 14 literature BEs Histogram indicates:  530.2 eV for Cr2O3 based on 14 literature BEs

Histogram indicates:  531.3 eV for -CO3 based on 13 literature BEs Histogram indicates:  532.9 eV for SiO2 based on 49 literature BEs

 

 

Table #6


NIST Database of O (1s) 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.

 

To view the NIST table of BEs for O (1s) click on the link above.

→  Periodic Table 

 


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 Oxygen-containing Materials

 

 

 

Expert Knowledge Explanations

 

 

 

Oxygen (O) in PET and Silicone Polymers

 

Peak-fits, BEs, FWHMs, and Peak Labels
PET, Mylar™
Polyethylene terephthalate, PET
.
Mylar, PET
O (1s) Spectrum – raw
film scraped with razor edge
charge referenced so C (1s) = 285.0 eV		 Mylar, PET
O (1s) Spectrum – peak-fit
film scraped with razor edge
charge referenced so C (1s) = 285.0 eV
.
Mylar, PET
C (1s) Spectrum – raw 
film scraped with razor edge
charge referenced so C (1s) = 285.0 eV		  Mylar, PET
C (1s) Spectrum – peak-fit
film scraped with razor edge
charge referenced so C (1s) = 285.0 eV
.
 Mylar, PET
Valence Band Spectrum 
film scraped with razor edge
charge referenced so C (1s) = 285.0 eV		  Mylar, PET
O Auger Spectrum 
film scraped with razor edge
charge referenced so C (1s) = 285.0 eV
   

 

Survey Spectrum of Poly-ethylene terephthalate, PET  (Mylar™)

with Peaks Integrated, Assigned and Labelled

 

 

Silicone Oil (PDMS)
Poly-dimethyl siloxane
  .
Silicone Oil, PDMS
O (1s) Spectrum – raw
charge referenced so C (1s) = 285.0 eV		 Silicone Oil, PDMS
O (1s) Spectrum – peak-fit
charge referenced so C (1s) = 285.0 eV
  .
Silicone Oil, PDMS
Si (2p) Spectrum – raw
charge referenced so C (1s) = 285.0 eV		 Silicone Oil, PDMS
Si (2p) Spectrum – peak-fit
charge referenced so C (1s) = 285.0 eV
  .
Silicone Oil, PDMS
C (1s) Spectrum – raw
charge referenced so C (1s) = 285.0 eV		 Silicone Oil, PDMS
C (1s) Spectrum – peak-fit
charge referenced so C (1s) = 285.0 eV

 


Survey Spectrum of Poly-dimethyl siloxane (PDMS) 
with Peaks Integrated, Assigned and Labelled
 

 

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 Oxygen

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.

Copyright ©:  The XPS Library 

 

 

XPS Facts, Guidance & Information

→  Periodic Table 

    Element   Oxygen (O)
  
    Primary XPS peak used for Peak-fitting :   O (1s)  
    Spin-Orbit (S-O) splitting for Primary Peak:   NO Spin-Orbit splitting for “s” orbitals.
  
    Binding Energy (BE) of Primary XPS Signal:   530 eV
  
    Scofield Cross-Section (σ) Value:   O (1s) = 2.93
  
    Conductivity:      
    Range of O (1s) Chemical State BEs:   525 – 535 eV range  
    Signals from other elements that overlap
O (1s) Primary Peak:		   Sb (3d), Pd (3d), Na (Auger), V (2p)  
    Bulk Plasmons:   ~xxx eV above peak max for pure  
    Shake-up Peaks:   ??  
    Multiplet Splitting Peaks:   xx  

 

 

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

xx 

  

Copyright ©:  The XPS Library 

 

Information Useful for Peak-fitting O (1s)

  • FWHM (eV) for O (1s) peak in metal oxides:  ~1.0 -1.2 eV using 25 eV Pass Energy after ion etching:
  • FWHM (eV) of O (1s) peak in sulfates (SO4):  ~1.8 eV using 50 eV Pass Energy  (before ion etching)
  • Binding Energy (BE) of Primary Signal used for Measuring Chemical State Spectra:  530 eV for O (1s) in Metals with +/- 0.2 uncertainty
  • List of XPS Peaks that can Overlap Peak-fit results for O (1s):  Sb (3d), Pd (3d), Na (Auger), V (2p)

→  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.
  • 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 Metal Oxides

  • METAL Oxide thin films often have a low level of iron (Fe) in the bulk as a contaminant or to strengthen the thin film
  • METAL Oxide degrades slightly 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), Oxygen (N) and Oxygen (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 O (1s) 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

→  Periodic Table 

 

Data Collection Settings for Oxygen (O)

  • Primary Peak (XPS Signal) used to measure Chemical State Spectra:  O (1s) at 530 eV
  • Recommended Pass Energy for Measuring Chemical State Spectrum:  25-50 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:   520 – 540 eV
  • Recommended Extended BE Range for Measuring Chemical State Spectrum:  510 – 610 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 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 metals and various reactive surfaces.  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 

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Gas Phase XPS or UPS Spectra
 
 
     
     
     
     
     
     
     
     
     
 
 
 
 

 

Chemical State Spectra from Literature

from Thermo Scientific Website

 

 
 
 
 
 
 
 
 
 

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