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

 

Arsenic (As)

 

Arsenolite – As2O3 Arsenic – Aso Realgar – As2S4

 

  Page Index
  • Expert Knowledge & Explanations


Arsenic (Aso) Metalloid

Peak-fits, BEs, FWHMs, and Peak Labels

  .
Arsenic (Aso)
As (3d) Spectrum – raw spectrum, PE=10 eV		 Arsenic (Aso)
Peak-fit of As (3d) Spectrum (w/o asymm)
→  Periodic Table – HomePage  
Arsenic (Aso)
As (3d) Spectrum – raw – extended range 
 Arsenic (Aso)
As (2p) Spectrum – raw – extended range 
  .
Arsenic (Aso)
As (2p3/2) Spectrum – raw		 Arsenic (Aso)
As (2p3/2) Spectrum – Peak-fit

 

Survey Spectrum of Arsenic (Aso)
with Peaks Integrated, Assigned and Labelled

 

→  Periodic Table 

XPS Signals for Arsenic, (Aso)

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
  As (2p1/2) 1359.06 14.07 5.6
  As (2p3/2) 1323.36 27.19 6.3
  As (3s) 204 1.32 24.7
  As (3p1/2) 147 1.39 26.0
  As (3p3/2) 141 2.68 26.0
  As (3d3/2) 42.24 1.82 27.5
Ta (5p) overlaps As (3d5/2) 41.53 1.82 27.5
  As (4p) 3 0.121 xxx

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 As2O3:  3.5 – 4.0 eV  (https://materialsproject.org/)
Work Function for As:  xx eV

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

→  Periodic Table 

 

Valence Band Spectrum from Arsenic,  Aso
 Fresh exposed bulk produced by extensive Ar+ ion etching

 

 

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

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

 

As (LMM) Auger Peaks from Aso 
 Fresh exposed bulk produced by extensive Ar+ ion etching
Aso – main Auger peaks – peak-fit Aso – full Auger range
 

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Artefacts Caused by Argon Ion Etching

C (1s) from Carbide(s)

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

Argon Trapped in Aso

can form when Argon Ions are used
to removed surface contamination
   

 

Side-by-Side Comparison of
As Native Oxide & Arsenic Oxide (As2O3)
Peak-fits, BEs, FWHMs, and Peak Labels
As Native Oxide
As (3d) from As Native Oxide
Flood Gun OFF
As-Measured, C (1s) at 284.6 eV		 As2O3
As (3d) from As2O3 – pressed pellet
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
  . 
As Native Oxide As2O3
C (1s) from As Native Oxide

As-Measured, C (1s) at 284.6 eV (Flood Gun OFF)

C (1s) from As2O3 – pressed pellet
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
 
→  Periodic Table 
  . 
As Native Oxide As2O3
O (1s) from As Native Oxide
Flood Gun OFF
As-Measured, C (1s) at 284.6 eV

O (1s) from As2O3 – pressed pellet
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
  .
As Native Oxide
As (2p3/2) from As Native Oxide 
Flood Gun OFF
As-Measured, C (1s) at 284.6 eV		 As2O3
As (2p3/2) from As2O3 – pressed pellet
Flood Gun ON
Charge Referenced to C (1s) at 285.0 eV
na
→  Periodic Table

 

 

Survey Spectrum of Arsenic (As) Native Oxide
with Peaks Integrated, Assigned and Labelled

→  Periodic Table 

 

 

Survey Spectrum of Arsenic Oxide, As2O3
with Peaks Integrated, Assigned and Labelled

→  Periodic Table  

 

Overlays of As (3d) Spectra for
As Native Oxide and As2O3

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

 Overlay of Aso and As Native Oxide – As (3d)
Native Oxide C (1s) = 285.0 eV (Flood gun OFF)

  Overlay of Aso and As2O3 – As (3d)
Pure Oxide C (1s) = 285.0 eV
Chemical Shift: 3.6 eV
→  Periodic Table  Copyright ©:  The XPS Library 

 

Overlay of As (3d)
Aso, As Native Oxide, & As2O3   

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Valence Band Spectra
Aso, As2O3 

Aso
Ion etched clean		 As2O3 – pressed pellet
Flood gun is ON,  Charge referenced so C (1s) = 285.0 eV

Overlay of Valence Band Spectra
for Aso and As2O3

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Arsenic Minerals, Gemstones, and Chemical Compounds

 
Vincentite – Pd3As Arsenopyrite – FeAsS Laffittite – AgHgAsS3 Xanthoconite – Ag3AsS3

→  Periodic Table 

 

 

Six (6) Chemical State Tables of As (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

As (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
As 33 InAs (N*4) 40.6 eV 41.5 eV 284.8 eV Avg BE – NIST
As 33 GaAs (N*14) 40.8 eV 41.5 eV 284.8 eV Avg BE – NIST
As 33 GaAs 41.0 eV 41.7 eV 285.0 eV The XPS Library
As 33 AlGaAs 41.1 eV 41.4 eV 285.0 eV The XPS Library
As 33 GaInAs 41.4 eV   285.0 eV The XPS Library
As 33 As – element 41.8 eV   285.0 eV The XPS Library
As 33 As-2Se3 (N*5) 42.9 eV   284.8 eV Avg BE – NIST
As 33 As-2S3 43.7 eV   285.0 eV The XPS Library
As 33 As-I3 (N*1) 43.5 eV   284.8 eV Avg BE – NIST
As 33 As-4S4 43.9 eV   285.0 eV The XPS Library
As 33 As-2O3 (N*9) 44.1 eV 44.9 eV 284.8 eV Avg BE – NIST
As 33 Na-AsO2 (N*3) 44.2 eV 44.9 eV 284.8 eV Avg BE – NIST
As 33 As-2O5 44.9 eV   285.0 eV The XPS Library
As 33 As-2O5 (N*4) 45.7 eV 46.5 eV 284.8 eV Avg BE – NIST
As 33 As-F3 (N*1) 47.1 eV   284.8 eV Avg BE – NIST
As 33 As-(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

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

C (1s) BE = 284.8 eV

 

→  Periodic Table 

Copyright ©:  Ulvac-PHI

Table #3

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

C (1s) BE = 284.8 eV

Chemical state Binding energy (eV), As (3d5/2)
GaAs 40.8
As2O3 44.1
As3+ (GaAs native oxide) 44.8
As5+ (GaAs native oxide) 45.6

→  Periodic Table 

Copyright ©:  Thermo Scientific 

Table #4

As (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

As (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
As 3d5/2 InAs 40.7 ±0.3 40.4 ～ 40.9
As 3d5/2 GaAs 40.8 ±0.1 40.7 ～ 40.9
As 3d5/2 AlAs 41.0 ±0.2 40.8 ～ 41.2
As 3d5/2 AlGaAs 41.0 ±0.2 40.8 ～ 41.2
As 3d5/2 As 41.6 ±0.2 41.4 ～ 41.8
As 3d5/2 AsI3 43.5 ±0.3 43.2 ～ 43.7
As 3d5/2 Sulfides 43.6 ±0.5 43.1 ～ 44.0
As 3d5/2 As2O3 45.0 ±0.3 44.7 ～ 45.2
As 3d5/2 AsBr3 45.3 ±0.3 45.0 ～ 45.5
As 3d5/2 As2O5 46.1 ±0.2 45.9 ～ 46.3

→  Periodic Table 

 


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

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

Histogram indicates:  41.7 eV for Aso based on 13 literature BEs Histogram indicates:  44.8 eV for As2O3 based on 11 literature BEs

 

Table #6


NIST Database of As (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
As 3d GaAs/Y 39.60  Click
As 3d5/2 H2O/GaAs 40.20  Click
As 3d GaAs/Y 40.30  Click
As 3d5/2 GaAs 40.30  Click
As 3d5/2 H2S/GaAs 40.30  Click
As 3d5/2 GaAs 40.30  Click
As 3d In0.52Al0.48As 40.43  Click
As 3d5/2 UAs 40.47  Click
As 3d GaAs 40.60  Click
As 3d InAs 40.61  Click
As 3d In0.53Ga0.47As 40.69  Click
As 3d GaAs 40.70  Click
As 3d5/2 GaAs0.68 40.70  Click
As 3d5/2 GaAs0.87 40.70  Click
As 3d5/2 Au/GaAs 40.72  Click
As 3d5/2 In0.75Ga0.25As/InP 40.75  Click
As 3d5/2 In0.3Ga0.7As/InP 40.75  Click
As 3d GaAs 40.76  Click
As 3d5/2 InAs 40.78  Click
As 3d5/2 Ga0.47In0.53As 40.79  Click
As 3d GaAs 40.80  Click
As 3d NbAs 40.80  Click
As 3d5/2 Cl2/GaAs0.96 40.80  Click
As 3d5/2 Au/GaAs 40.80  Click
As 3d5/2 InAs 40.80  Click
As 3d GaAs 40.90  Click
As 3d As15In54Sb31 40.90  Click
As 3d Al0.4Ga0.6As 41.00  Click
As 3d AlAs 41.00  Click
As 3d AlAs 41.00  Click
As 3d GaAs 41.00  Click
As 3d GaAs 41.00  Click
As 3d GaAs 41.00  Click
As 3d GaAs 41.00  Click
As 3d GaAs 41.00  Click
As 3d GaAs 41.00  Click
As 3d (In,Ga)AsOx 41.00  Click
As 3d InAs 41.00  Click
As 3d InAs 41.00  Click
As 3d Ga0.47In0.53As 41.06  Click
As 3d5/2 GaAs 41.09  Click
As 3d GaAs 41.20  Click
As 3d GaAs 41.20  Click
As 3d GaAs 41.30  Click
As 3d GaAs 41.30  Click
As 3d (C2H5)3Ga/GaAs 41.30  Click
As 3d GaAsOx 41.30  Click
As 3d GaAs 41.33  Click
As 3d GaAs 41.34  Click
As 3d GaAs 41.40  Click
As 3d GaAs 41.40  Click
As 3d GaAs 41.40  Click
As 3d5/2 As 41.40  Click
As 3d5/2 O2/As/Si 41.48  Click
As 3d5/2 O2/As/Si 41.48  Click
As 3d5/2 O2/As/Si 41.48  Click
As 3d5/2 O2/As/Si 41.48  Click
As 3d5/2 O2/As/Si 41.48  Click
As 3d5/2 O2/As/Si 41.48  Click
As 3d5/2 O2/As/Si 41.48  Click
As 3d5/2 O2/As/Si 41.48  Click
As 3d5/2 O2/As/Si 41.48  Click
As 3d5/2 As/Si 41.48  Click
As 3d5/2 As/Si 41.48  Click
As 3d5/2 As/Si 41.48  Click
As 3d As 41.50  Click
As 3d As 41.50  Click
As 3d As 41.50  Click
As 3d As 41.50  Click
As 3d As 41.50  Click
As 3d InAs 41.50  Click
As 3d GaAs 41.50  Click
As 3d GaAs 41.50  Click
As 3d GaAs 41.50  Click
As 3d GaAs 41.50  Click
As 3d5/2 GaAs 41.50  Click
As 3d5/2 GaAs 41.56  Click
As 3d As 41.60  Click
As 3d GaAs 41.60  Click
As 3d5/2 As 41.62  Click
As 3d As 41.70  Click
As 3d As 41.80  Click
As 3d As 41.80  Click
As 3d5/2 GaAs 41.85  Click
As 3d As 41.90  Click
As 3d As 41.90  Click
As 3d As 41.90  Click
As 3d Ga2Mo5As4 41.90  Click
As 3d Cu4Mo5As4 41.90  Click
As 3d Mo5As4 41.90  Click
As 3d As 42.00  Click
As 3d As 42.00  Click
As 3d5/2 As2O/n-GaAs 42.00  Click
As 3d As 42.10  Click
As 3d [As(C6H5)3] 42.40  Click
As 3d As4S4 42.50  Click
As 3d [Tc((CH3)2AsC6H4As(CH3)2)2Br2]Br 42.60  Click
As 3d As2S3 42.70  Click
As 3d [As(C6H5)3] 42.76  Click
As 3d [As(C6H5)3] 42.80  Click
As 3d As2Se3 42.90  Click
As 3d As2Se3 42.90  Click
As 3d As2Se3 42.90  Click
As 3d As2Se3 42.90  Click
As 3d As2S3 42.90  Click
As 3d As2Se3 43.00  Click
As 3d As40Bi10Se50 43.00  Click
As 3d [As(C6H5)3] 43.10  Click
As 3d As4S4 43.10  Click
As 3d [W(CO)5(As(C6H5)3)] 43.21  Click
As 3d [Mo(CO)5(As(C6H5)3)] 43.24  Click
As 3d [CoCl2(C6H4(As(CH3)2)2)]ClO4 43.30  Click
As 3d [Fe(NO)I(C6H4(As(CH3)2)2)]I 43.30  Click
As 3d [BBr3(As(C6H5)3)] 43.30  Click
As 3d As40Bi4Se56 43.30  Click
As 3d [Cr(CO)5(As(C6H5)3)] 43.37  Click
As 3d [CoH2(C6H4(As(CH3)2)2)]ClO4 43.40  Click
As 3d As2S3 43.40  Click
As 3d [MnBr(CO)4(As(C6H5)3)] 43.50  Click
As 3d [Fe(NCS)2(C6H4(As(CH3)2)2)2] 43.50  Click
As 3d [FeCl(NO2)(C6H4(As(CH3)2)2)] 43.50  Click
As 3d AsI3 43.50  Click
As 3d CH3AsI2 43.50  Click
As 3d As2S5 43.50  Click
As 3d [CoBr2(C6H4(As(CH3)2)2)2] 43.60  Click
As 3d [AuCl(As(C6H5)3)] 43.60  Click
As 3d [PdCl2((C6H5)2AsCH2As(C6H5)2)2] 43.60  Click
As 3d [As(CH3-C6H4)3]2ClRuCl3RuCl[As(CH3-C6H4)3]2 43.60  Click
As 3d [As(CH3-C6H4)3]3RuCl3RuCl2[As(CH3-C6H4)3] 43.60  Click
As 3d As2Se3 43.70  Click
As 3d [As(CH3-C6H4)3]2ClRuCl3RuCl2[As(CH3-C6H4)3] 43.70  Click
As 3d [FeCl2(C6H4(As(CH3)2)2)2] 43.80  Click
As 3d [BI3(As(C6H5)3)] 43.88  Click
As 3d [As(CH3)3]S 43.90  Click
As 3d As2O3 43.90  Click
As 3d [As(C6H5)3]S 44.10  Click
As 3d As2O3 44.10  Click
As 3d [AsS(C6H5)3] 44.16  Click
As 3d (C6H5)3As(CHCOOCH3) 44.20  Click
As 3d [AsO(C6H5)3] 44.20  Click
As 3d [(C6H5)3As(CHCOC6H5)] 44.20  Click
As 3d NaAsO2 44.20  Click
As 3d As2O3 44.20  Click
As 3d [As(C6H5)3(CH3)]Br 44.20  Click
As 3d [(C6H5)3AsCH3]Br 44.20  Click
As 3d [AsO(C6H5)3] 44.30  Click
As 3d NaAsO2 44.30  Click
As 3d [As((C6H5)2OOH)] 44.40  Click
As 3d [AsO(C6H5)3] 44.40  Click
As 3d As2O3 44.40  Click
As 3d K3AsO4 44.40  Click
As 3d As2S5 44.40  Click
As 3d [(OH)2As(C6H5)3] 44.50  Click
As 3d (CH3)2AsOOH 44.50  Click
As 3d5/2 AsO/n-GaAs 44.50  Click
As 3d [As(C6H5)4]Br 44.53  Click
As 3d [As(C6H5)4]I 44.61  Click
As 3d [As(C6H5)4]Br 44.70  Click
As 3d [(C6H5)3As(CH2C(O)C6H5)]Br 44.70  Click
As 3d As2O3 44.70  Click
As 3d As2O3 44.70  Click
As 3d GaAsOx 44.70  Click
As 3d As2O3 44.80  Click
As 3d As2O3 44.80  Click
As 3d As2O3 44.90  Click
As 3d Na3AsO4 44.90  Click
As 3d NaAsO2 44.90  Click
As 3d As2O3 44.90  Click
As 3d As2O3 44.90  Click
As 3d5/2 As2O3 44.90  Click
As 3d C4H10HAsO3 45.00  Click
As 3d As2O3 45.00  Click
As 3d As2O3 45.00  Click
As 3d NaAsO2 45.00  Click
As 3d5/2 As2O3/n-GaAs 45.00  Click
As 3d (C6H5)As(O)(OH)2 45.10  Click
As 3d NaAsO3 45.20  Click
As 3d AsBr3 45.30  Click
As 3d As2O3 45.40  Click
As 3d Na4As2O7 45.40  Click
As 3d (In,Ga)AsOx 45.40  Click
As 3d Na2HAsO4 45.50  Click
As 3d InAsO4 45.50  Click
As 3d Na2HAsO4 45.60  Click
As 3d As2O5 45.70  Click
As 3d As2O5 45.80  Click
As 3d As2O5 45.80  Click
As 3d Ga(AsO3)3 45.80  Click
As 3d5/2 As2O5/n-GaAs 45.80  Click
As 3d As2O5 45.90  Click
As 3d (C6H5)As(O)(OH)2 46.10  Click
As 3d As2O5 46.10  Click
As 3d As2O5 46.10  Click
As 3d GaAsO4 46.10  Click
As 3d As2O3 46.30  Click
As 3d As2O5 46.30  Click
As 3d As2O5 46.50  Click
As 3d KH2AsO4 46.70  Click
As 3d (C6H5CHCHC6H4CHCHC6H5)(AsF5)2.9 46.80  Click
As 3d AsF5 47.10  Click
As 3d AsF3 47.10  Click
As 3d KAsF6 47.80  Click
As 3d KAsF6 47.80  Click
As 3d KAsF6 48.10  Click
As 3d (C6H5CHCHC6H4CHCHC6H5)(AsF5)2.9 48.20  Click
As 3d LiAsF6 49.40  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 Arsenic Materials

 

 

Expert Knowledge Explanations

→  Periodic Table 

 

Arsenic Chemical Compounds

 

Peak-fits and Overlays of Chemical State Spectra

Pure Arsenic:  As (3d)
Cu (2p3/2) BE = 932.6 eV		 As2O3:  As (3d)
C (1s) BE = 285.0 eV		 AsF3: As (3d)
C (1s) BE = 285.0 eV
 

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Overlay of As (3d) Spectra shown Above

C (1s) BE = 285.0 eV

 

 

Chemical Shift between As and As2O3:  xxx eV
 Chemical Shift between As and AsF3:  xxx eV

 

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Arsenic Oxide (As2O3)
pressed pellet

Survey Spectrum from As2O3
Flood gun is ON, C (1s) BE = 285.0 eV
 As (3d) Chemical State Spectrum from As2O3
Flood gun is ON, C (1s) BE = 285.0 eV
  . 
O (1s) Chemical State Spectrum from As2O3
Flood gun is ON, C (1s) BE = 285.0 eV
 C (1s) Chemical State Spectrum from As2O3
Flood gun is ON, C (1s) BE = 285.0 eV
  . 
Valence Band Spectrum from As2O3
Flood gun is ON, C (1s) BE = 285.0 eV
 As (2p3/2) Chemical State Spectrum from As2O3
Flood gun is ON, C (1s) BE = 285.0 eV

Features Observed

  • xx
  • xx
  • xx

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Arsenic Chemical Compounds

 

Arsenic Pentoxide, As2O5

Survey Spectrum As (3d) Spectrum
   .
C (1s) Spectrum O (1s) Spectrum
  .
Valence Band Spectrum  
 
   
   

 

Arsenic Sulfide, As2S3
Orpiment

Survey Spectrum As (3d) Spectrum
  .
C (1s) Spectrum S (2p) Spectrum
  .
Valence Band Spectrum As (2p3/2) Spectrum
   
   

 

Gallium Arsenide, GaAs wafer
Freshly exposed bulk

Flood Gun On at 0.1 eV

Survey Spectrum As (3d) Spectrum
   .
Ga (2p3/2) Spectrum Ga (3d) Spectrum
  .
Valence Band Spectrum As (2p3/2) Spectrum
   
   

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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 Arsenic – As2O3

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.

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Flood Gun Effect on Native Oxide of Arsenic

 

Native Oxide of Arsenic Sheet – Sample Grounded

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

As (3d) O (1s) C (1s)
 
     
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XPS Study of UHV Gas Captured by Freshly Ion Etched Arsenic
 
Reveals Chemical Shifts and Chemical States that Develop from Highly Reactive Pure Aso

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

   
XxCu XxCu
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XxCu XxCu

 

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XPS Facts, Guidance & Information

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    Element   Arsenic (As)
  
    Primary XPS peak used for Peak-fitting:   As (3d)  
    Spin-Orbit (S-O) splitting for Primary Peak:   Spin-Orbit splitting for “d” Orbital, ΔBE = 0.55 eV
  
    Binding Energy (BE) of Primary XPS Signal:   41.6 eV
  
    Scofield Cross-Section (σ) Value:   As (3d5/2) = 1.08.     As (3d3/2) = 0.741
  
    Conductivity:   As resistivity =  
Native Oxide suffers Differential Charing		  
    Range of As (3d5/2) Chemical State BEs:   41 – 46 eV range   (Aso to AsF3)  
    Signals from other elements that overlap
As (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 

  

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

  • FWHM (eV) of As (3d5/2) for Pure Aso :  ~0.65 eV using 25 eV Pass Energy after ion etching:
  • FWHM (eV) of As (3d5/2) for As2O3:  ~1.1 eV using 50 eV Pass Energy  (before ion etching)
  • Binding Energy (BE) of Primary Signal used for Measuring Chemical State Spectra:  41.6 eV for As (3d5/2) with +/- 0.2 uncertainty
  • List of XPS Peaks that can Overlap Peak-fit results for As (3d5/2):  xxx

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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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Contaminants Specific to Arsenic

  • Arsenic develops a thin native oxide due to the reactive nature of clean Arsenic .
  • The native oxide of As Ox is 1-2 nm thick.
  • Arsenic thin films often have a low level of iron (Fe) in the bulk as a contaminant or to strengthen the thin film
  • Arsenic 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

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Data Collection Guidance

  • Chemical state differentiation can be difficult
  • Collect principal As (3d) peak as well as As (2p3/2).
  • 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

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Data Collection Settings for Arsenic (As)

  • Conductivity:  Metals readily develop 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:  As (3d5/2) at 41.6 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:  36 – 56 eV
  • Recommended Extended BE Range for Measuring Chemical State Spectrum:  30 – 80eV
  • 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 As 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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Gas Phase XPS or UPS Spectra
 
 
     
     
     
     
     
     
     
     
     
 
 
 
 

 

Chemical State Spectra from Literature
 
 
from Thermo website
 
 
 
 
 
 

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