Anthracite Coal Amorphous C CNT Diamond Graphene Graphene Oxide HOPG RGO Vaseline Paraffin Wax
AlTiC Cr3C2 HfC Mo2C NbC SiC TiC VC WC ZrC
Ag2CO3 BaCO3 CaCO3 FeCO3 KHCO3 K2CO3 Li2CO3 MgCO3 NaHCO3 Na2CO3
HDPE PP PS Methyl Cellulose Krytox PET – Mylar Kapton PVC Teflon  

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


Carbon (C)

Inorganic Types of Carbon**

Graphene – Co Natural Graphite – Carbon, Co Highly Oriented Pyrolytic Graphite (HOPG) – Co

** Organic Types of Carbon are presented in the XPS Database of Polymers

 

  Page Index

 


Carbon (Co) – HOPG

Peak-fits, BEs, FWHMs, and Peak Labels

Carbon (Co)
Highly Oriented Pyrolytic Graphite (HOPG)
C (1s) Spectrum – raw spectrum
fresh bulk exposed by delaminating HOPG		 Carbon (Co)
Highly Oriented Pyrolytic Graphite (HOPG)
Peak-fit of C (1s) Spectrum (w/o peak asymmetry)
fresh bulk exposed by delaminating HOPG
→  Periodic Table 

 

 
Carbon (Co)
Highly Oriented Pyrolytic Graphite (HOPG)
C (1s) Spectrum – raw spectrum
Vertically Expanded to show Detail		 Carbon (Co)
Highly Oriented Pyrolytic Graphite (HOPG)
C (1s) Spectrum – Peak-fit
with Asymmetry and minimum added peaks (4)

   
Carbon (Co)
Highly Oriented Pyrolytic Graphite (HOPG)
Valence Band spectrum
 fresh bulk exposed by delaminating HOPG		 Carbon (Co)
Highly Oriented Pyrolytic Graphite (HOPG)
C (KLL) Auger Signal by XPS
fresh bulk exposed by delaminating HOPG

 

Survey Spectrum of Carbon (Co) HOPG
with Peaks, Integrated, Assigned and Labelled
freshly delaminated HOPG in lab air

→  Periodic Table

 


XPS Signals for Carbon, Co HOPG

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
K (2p) & Ru (3d) overlap C (1s) 284.5 1.00 33.0
Hf (4f) overlaps C (2s) 18 0.0015 38.7

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

Intrinsic Plasmon Peak:  ~29 eV above peak max
Expected Bandgap for HOPG – Carbon : ~40 meV
Expected Bandgap for Natural Diamond : ~5.5 eV

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

→  Periodic Table

 

Plasmon Peaks for HOPG, Co
 Freshly delaminated HOPG in lab air

C (1s) – Extended Range Spectrum C (1s) – Extended Range Spectrum – Vertically Zoomed
fresh bulk exposed by delaminating HOPG fresh bulk exposed by delaminating HOPG

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table – HomePage 

 

Side-by-Side Comparison of
HOPG & Diamond
Peak-fits, BEs, FWHMs, and Peak Labels
HOPG – Co Diamond – Co
C (1s) from HOPG (delaminated)
Flood Gun OFF
exposed bulk – freshly delaminated		 C (1s) from Black Diamond (crystal)
Flood Gun OFF
As-Received, surface contaminated

 

Overlay of C (1s) Spectra
HOPG (delaminated) and Black Diamond (as received)

No Ar+ ion etching

→  Periodic Table – HomePage 
  .
HOPG – Co
Valence Bands from freshly delaminated HOPG
As-Measured, C (1s) at 286.8 eV (Flood Gun OFF)
 

Black Diamond – Co
Valence Bands from as received Black Diamond (crystal)
Flood Gun OFF
As-Received, surface contaminated with Si, and trace N, Zn

 

Overlay of Valence Band Spectra
HOPG (delaminated) and Black Diamond (as received)
No Ar+ ion etching

→  Periodic Table – HomePage 

 

Survey Spectrum of HOPG, Co
freshly delaminated
with Peaks Integrated, Assigned and Labelled

 

Survey Spectrum of Black Diamond, Co
with Peaks Integrated, Assigned and Labelled

→  Periodic Table – HomePage   

 

Valence Band Spectra and Overlay
Black Diamond (as received) and
Industrial Diamond (after ion etching with Ar+)

 

Black Diamond, Co
As Received
NOT Ion Etched
 Industrial Diamond, Co
Cleaned with Solvents
Ion Etched with Ar+

→  Periodic Table – HomePage  Copyright ©:  The XPS Library 

 

Overlay of Valence Band Spectra
Black Diamond and Industrial Diamond
labelling peaks due to Ar (3p) and Ar (3s) from Ar+ ion etch

Features Observed

  • xx
  • xx
  • xx

→  Periodic Table 

 

Effect of Ion Etching Diamond
(Due to ion etching one narrow peak becomes 2 or 3 peaks at lower BE)
Overlay of Industrial Diamond As Received versus Ion Etched
Flood Gun ON, 2 eV

Expanded View of Chemical Shift

→  Periodic Table – HomePage  

 

Graphene Forms of Carbon

 

Survey Spectrum of Graphene
with Peaks Integrated, Assigned and Labelled

→  Periodic Table – HomePage 

C (1s) of Graphene – raw spectrum C (1s) of Graphene – peak-fit

 

 
Valence Band Spectrum of Graphene Valence Band Spectrum of HOPG for comparison

 

Survey Spectrum of Graphene Oxide (GO)
with Peaks Integrated, Assigned and Labelled

→  Periodic Table – HomePage 

Graphene Oxide, pressed
C (1s) spectrum – raw		 Graphene Oxide, pressed
C (1s) spectrum – peak-fit
   
Graphene Oxide, pressed
O (1s) spectrum – raw		 Graphene Oxide, pressed
O (1s) spectrum – peak-fit

→  Periodic Table – HomePage 

 

 
Graphene Oxide, pressed
Valence Band		 Graphene

 

Survey Spectrum of Reduced Graphene Oxide (RGO)
with Peaks Integrated, Assigned and Labelled


→  Periodic Table – HomePage 

Reduced Graphene Oxide (RGO)
C (1s) – raw		 Reduced Graphene Oxide (RGO)
C (1s) – peak-fit

 

 
Overlay of C (1s) from
Graphene and Reduced Graphene Oxide (RGO)		 Overlay of C (1s) from
Graphene and Graphene Oxide

→  Periodic Table – HomePage 

 

 
Overlay of C (1s) from
Graphene, Graphene Oxide, and Reduced Graphene Oxide (RGO)		 Reduced Graphene Oxide (RGO)
Valence Band Spectrum

Features Explained

  • Graphene C (1s) is a mirror of HOPG which is why the VB spectra are effectively identical
  • The sp2 peak component represents a conductor so it has an asymmetric tail.
  • Graphene oxide has a complex C1s spectrum that includes sp2, sp3, C-O and C=O peaks.
  • The sp3 carbon and functionalized carbon of graphene oxide should be fitted with normal symmetric peak shapes.
  • The sp3 carbon peak should be ~0.9 eV higher than the sp2 peak.

 

 

Adventitious Carbon

What is Adventitious Carbon ?

  The chemical composition of “adventitious carbon”, which has been widely used for charge referencing of insulators, has never been definitively determined by any analytical method, even though ToF-SIMS and GC–MS could be used to reveal more about this type of carbon. Airborne Molecular Carbon (AMC) is another name.  
 
 
  It is important to note that the ratio of the different types of adventitious carbon chemical state moieties (hydrocarbon, alcohol, ether, ketone, ester, acid, carbonate) changes in accordance with the basic chemical nature of the substrate (e.g. metal, glass, ceramic, oxide, polymer) and the origins of the adventitious carbon.  
 
 
  Adventitious hydrocarbons are convenient as a rough or crude reference energy because it and various types of oxygen appear on the surface of almost every material or product, but there are many variables that you must accept or deal with if you try to use adventitious hydrocarbons as a reference energy.  
 
 
  Adventitious carbon will contain different types of carbon depending on the contaminations that exist in the “production” room, the “packaging” room, the “storage” room, the contamination inside the plastic bag or plastic box used to store the material.  
 
 
  The type and nature of adventitious carbon also depends on your location around the world.  Are you near a forest that releases all sorts of pine oils or other tree products?  Are you located in a major city that has all sorts of air pollution that will eventually attach itself to a freshly made surface which is your product. Are you located near the ocean or a big lake?  These are also sources of airborne organic matter that can attach itself to your surfaces.  Is your company making chemicals?  Some of the gases from chemicals will move around.  You may not smell them, but they might be there in the PPM or PPM level.  
 
 
  It is interesting to note that the ratio of the different types of adventitious carbon chemical state moieties (hydrocarbon, alcohol, ether, ketone, ester, acid, carbonate) changes in accordance with the basic chemical nature of the substrate (e.g. metal, glass, ceramic, oxide, polymer). The as-received fully passivated surface of a metal often has 40–60 at.% of adventitious carbon on it, whereas polished glasses and ceramics have 20–40 at.% of adventitious carbon and polymers have only 1–10 at.%.  The C (1s) spectra shown below reveal the various levels and types of adventitious carbon that collect on different materials.  The Magnesium and Lead native oxides collect CO2 gas from the air and form Carbonates.  The formation can be direct or the native oxide may form a Hydroxide that then adsorbs the CO2 from the air.  
 
 
→  Periodic Table – HomePage  Charge referencing is performed by mathematically correcting all experimental peak values to a suitable reference energy, which in the case of non-conductive materials, is normally the C 1 s BE of the covalently bonded, non-ionic, hydrocarbon (component) moieties (C-H, C-C, C=C, CxHy) that exist on the “as-received” surface of nearly all materials. This hydrocarbon moiety (component) is the dominant form of adventitious carbon on all materials if the sample has not been recently ion etched, fractured in vacuum, or specially treated to remove the adventitious carbon.  

 

 

Different Types of Adventitious Carbon
that form on Different Materials

 

 

 Different Amounts of Adventitious Carbon
on Different Materials

Source:  Air-borne Carbon materials, Contaminants on inside surface of storage bags or boxes, Contamination by touching with gloves or fingers or tools, 
cleaning agents, air pollutants

 

Inorganic Carbonate (CO3) forms of Carbon

 

Survey Spectrum of Potassium Carbonate, K2CO3
(crystallites, freshly ground)
with Peaks Integrated, Assigned and Labelled

C (1s) Spectra of K2CO3
(crystallites, freshly ground)		 O (1s) Spectra of K2CO3
(crystallites, freshly ground)

 

 

Survey Spectrum of Potassium Bi-Carbonate, K-HCO3
(crystallites, freshly ground)
with Peaks Integrated, Assigned and Labelled

C (1s) Spectra of K-HCO3
(crystallites, freshly ground)		 O (1s) Spectra of K-HCO3
(crystallites, freshly ground)

→  Periodic Table – HomePage 

 

 

Overlay of C (1s) from:

Carbonate (-CO3) and bi-Carbonate (-HCO3)

Chemical Shift = 0.9 eV BE difference
comparing K2CO3 and KHCO3
Flood Gun ON, charge referenced so C (1s) = 285.0 eV

 

Expanded View of C (1s) Overlay
reveals a 0.9 eV difference between -CO3 and -HCO3


O (1s) Overlay reveals a 1.5 eV difference
between -CO3 and -HCO3 

→  Periodic Table – HomePage 

 

Survey Spectrum from Calcium Carbonate, CaCO3
Iceland Spar Calcite, Single Crystal, freshly exposed bulk
with Peaks Integrated, Assigned and Labelled
Flood Gun ON, charge referenced so C (1s) = 285.0 eV

 

Expanded View
of Carbon, Potassium and Oxygen Signals in Survey

 

Expanded View
of Calcium (3s and 3p) and Valence Band Signals in Survey

C (1s) Spectrum from CaCO3 – raw
Charged referenced to C (1s) at 285.0 eV		 C (1s) Spectrum from CaCO3 – Peak-fit
Charged referenced to C (1s) at 285.0 eV
CO3 – carbonate chemical shift = 4.8 eV

 

 
O (1s) Spectrum from CaCO3 – raw
Charged referenced to C (1s) at 285.0 eV		 O (1s) Spectrum from CaCO3 – peak-fit
Charged referenced to C (1s) at 285.0 eV

 

 
Ca (2p) Spectrum from CaCO3 – raw
Charged referenced to C (1s) at 285.0 eV		 Ca (2p) Spectrum from CaCO3 – peak-fit
Charged referenced to C (1s) at 285.0 eV

 

 
Valence Band Spectrum from CaCO3 – raw
Charged referenced to C (1s) at 285.0 eV		 CaCO3, Iceland Spar Calcite

 

 

 

 

 

 

Spectra from cubic Silicon Carbide, c-SiC
(as received and very soft ion etch)
c-SiC, polished optical element, Bandgap ~2.3
Flood Gun ON at 1 eV, charge referenced so C (1s) = 285.0 eV

C (1s) Spectrum from c-SiC – as received – raw
Charged referenced to C (1s) at 285.0 eV		 Si (2p) Spectrum from c-SiC – as received – peak-fit
Charged referenced to C (1s) at 285.0 eV
   

Si (2p) Spectrum from c-SiC – as received – raw
Charged referenced to C (1s) at 285.0 eV

 Si (2p) Spectrum from c-SiC – as received – peak-fit
Charged referenced to C (1s) at 285.0 eV
   
Si (2p) Spectrum from c-SiC – after light ion etch – raw
Charged referenced to C (1s) at 285.0 eV		 Si (2p) Spectrum from c-SiC – after light ion etch – peak-fit
Charged referenced to C (1s) at 285.0 eV

 

 
Valence Band Spectrum from c-SiC – raw
Charged referenced to C (1s) at 285.0 eV		 SiC boule

 

 

HomePage 


Overlay of C (1s) Spectra
from
HOPG, Diamond, and c-SiC

 

→  Periodic Table – HomePage 

 

Carbon Minerals, Gemstones, and Chemical Compounds

 

Natural Yellow Diamond – Co Natural Pink Diamond – Co Man-made Diamond – Co Iceland Spar Calcite – CaCO3
       
       
Carbonate Minerals – MxCO3 Natural Silicon Carbide – SiC
(from meteorite)		 Calcium Carbide – CaC Edscottite – Fe5C2
(from meteorite)
       
       

 

Five (5) Chemical State Tables of C (1s) BEs

 

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

C (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
C 6 range for carbides, C2- 281.5 – 284.2 eV   285.0 eV The XPS Library
C 6 c-SiC 282.9 eV   285.0 eV The XPS Library
C 6 SiCN 284.3 eV     The XPS Library
C 6 C-HOPG 284.5 eV   285.0 eV The XPS Library
C 6 C, aromatic, sp2 284.6 eV 284.8 eV 285.0 eV The XPS Library
C 6 C=C 284.7 eV 284.8 eV 285.0 eV The XPS Library
C 6 C-Si 284.8 eV 285.1 eV 285.0 eV The XPS Library
C 6 C-C, C-H 285.0 eV   285.0 eV The XPS Library
C 6 C, diamond, sp3 285.1 eV 285.2 eV 285.0 eV The XPS Library
C 6 C-SOx 285.2 eV 285.8 eV 285.0 eV The XPS Library
C 6 C-N 285.6 eV 286.5 eV 285.0 eV The XPS Library
C 6 C-O-C,C-OH 286.0 eV 286.5 eV 285.0 eV The XPS Library
C 6 C-H2-CF2 286.4 eV 286.8 eV 285.0 eV The XPS Library
C 6 C nitrile 286.7 eV   285.0 eV The XPS Library
C 6 C-Cl 287.0 eV   285.0 eV The XPS Library
C 6 C-HF-CH2 287.3 eV 288.0 eV 285.0 eV The XPS Library
C 6 C=O 287.8 eV 288.0 eV 285.0 eV The XPS Library
C 6 C=N-O 288.0 eV 288.7 eV 285.0 eV The XPS Library
C 6 RbOAc 288.1 eV   285.0 eV The XPS Library
C 6 C-OOR,COOH 288.3 eV 289.2 eV 285.0 eV The XPS Library
C 6 C imide 288.5 eV 288.8 eV 285.0 eV The XPS Library
C 6 BaOAc 288.6 eV   285.0 eV The XPS Library
C 6 C-Cl2 288.6 eV   285.0 eV The XPS Library
C 6 C-O3 (metal) 288.8 eV 290.2 eV 285.0 eV The XPS Library
C 6 HC-O3 (metal) 289.5 eV 291.0 eV 285.0 eV The XPS Library
C 6 C-O3 org 289.5 eV 291.0 eV 285.0 eV The XPS Library
C 6 C-F2-CH2 289.8 eV 291.1 eV 285.0 eV The XPS Library
C 6 C-F2-CF2 291.3 eV 292.0 eV 285.0 eV The XPS Library
C 6 C pi-pi* 291.5 eV 292.1 eV 285.0 eV The XPS Library
C 6 C-F3 293.1 eV 293.8 eV 285.0 eV The XPS Library
C 6 C-F2O 294.1 eV   285.0 eV The XPS Library
C 6 C-F3O 295.2 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 (1s3/2) 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

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

C (1s) BE = 284.8 eV

→  Periodic Table 

Copyright ©:  Ulvac-PHI

Table #3

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

C (1s) BE = 284.8 eV

Chemical state Binding energy C1s / eV
C-C 284.8
C-O-C ~286
O-C=O ~288.5

→  Periodic Table 

Copyright ©:  Thermo Scientific 

Table #4

C (1s) Chemical State BEs from:  “XPSfitting” Website

Chemical State BE Table derived by peak-fitting contamination on Poly-ethylene polymer
C (1s) BE = 285.0 eV

 

→  Periodic Table 

Copyright ©:  Mark Beisinger

Table #5

C (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
C 1s Carbide 281.9 ±1.2 280.7 ～ 283.0
C 1s Carbon 284.6 ±0.5 284.1 ～ 285.1
C 1s Alcohols 286.4 ±0.4 286.0 ～ 286.8
C 1s C with S 286.5 ±1.1 285.4 ～ 287.5
C 1s C with Cl 286.7 ±1.2 285.5 ～ 287.8
C 1s C with N 286.9 ±1.7 285.2 ～ 288.5
C 1s Ethers 287.1 ±0.9 286.2 ～ 288.0
C 1s Ketones/Aldehydes 287.6 ±0.5 287.1 ～ 288.1
C 1s Carboxyls 288.6 ±0.6 288.0 ～ 289.2
C 1s CHF 289.0 ±1.3 287.7 ～ 290.2
C 1s Carbonates 290.3 ±1.3 289.0 ～ 291.6
C 1s CF2 292.0 ±0.4 291.6 ～ 292.4
C 1s CF3 293.0 ±0.5 292.5 ～ 293.5

→  Periodic Table 

 


Histograms of NIST BEs for C (1s) BEs

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

 

Histogram indicates:  292.4 eV for CF2 based on 5 literature BEs Histogram indicates:  282.9 eV for SiC based on 6 literature BEs

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

→  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 Carbon Materials

 

 

XPS Study of Carbide Formation due to:
Reaction of UHV Gas Capture with Freshly Ion Etched Metal Surfaces

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.
 
 
Carbides Formed due to reaction between now Reactive Metal Surfaces and UHV Gases
These C (1s) Montage plots show Carbide peaks in the 282-284 eV range.  Tungsten was expected to show a carbide but does not.
 
 
 
 
The Amount of Carbide that formed Overnight is Too Small to produce
an observable Metal (carbide) Peak adjacent to the Metal Peak
The corresponding Metal Signals do not exhibit the small Carbide peaks which are very close to the Metal Peak
 
 
 
 
Copyright ©:  The XPS Library

 


Carbon Auger (KLL) Spectra from Various Materials
measured by XPS at ~1220 eV

Various Materials show various peak-shapes
potentially useful for Charge Referencing true Auger Spectra

→  Periodic Table – HomePage 

 

Auger Spectra of HOPG by AES
using High Energy Resolution Settings (0.05 %)

Auger Survey Spectrum from HOPG, Co  (direct mode) Auger C (KLL) Spectrum from HOPG, Co  (direct mode)
peak at 211 eV is due to implanted Ar+

 

 

Slow XPS Depth Profile of 20 Ang of Carbon Deposited on 10 Ang Cr / Ni(P)

C (1s) Montage shows existence of Chromium Carbide that formed as Carbon was deposited on top of 10 Ang thick Chromium Film

 

→  Periodic Table – HomePage 

 

XPS Facts, Guidance & Information

→  Periodic Table 

    Element   Carbon (C)
  
    Primary XPS peak used for Peak-fitting :   C (1s)  
    Spin-Orbit (S-O) splitting for Primary Peak:   NO Spin-Orbit splitting for “s” orbital,
  
    Binding Energy (BE) of Primary XPS Signal:   284.5 eV
  
    Scofield Cross-Section (σ) Value:   C (1s) = 1.00
  
    Conductivity:   C resistivity = xx  
    Range of C (1s) Chemical State BEs:   281 – 294 eV range   (C2- to CF3)  
    Signals from other elements that overlap
C (1s) Primary Peak:		   Ru (3d3/2)  
    Bulk Plasmons:   ~xx eV above peak max for pure  
    Shake-up Peaks:   ??  
    Multiplet Splitting Peaks:   not possible  

 

 

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

xx 

  

Copyright ©:  The XPS Library 

 

Information Useful for Peak-fitting C (1s)

 

  • FWHM (eV) of C (1s) for Pure Co :  <0.8 eV using 25 eV Pass Energy after ion etching:
  • FWHM (eV) of C (1s) for CO3 xtal:  ~1.3 eV using 50 eV Pass Energy  (before ion etching)
  • Binding Energy (BE) of Primary Signal used for Measuring Chemical State Spectra:  284.5 eV for C (1s) with +/- 0.1 uncertainty
  • List of XPS Peaks that can Overlap Peak-fit results for C (1s):  Ru (3d)

→  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 Carbon

 

  • Carbon thin films often have a low level of iron (Fe) in the bulk as a contaminant or to strengthen the thin film
  • Carbon 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 C (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 Carbon (C)

 

  • Primary Peak (XPS Signal) used to measure Chemical State Spectra:  C (1s) at 284.5 eV
  • Recommended Pass Energy for Measuring Chemical State Spectrum:  40-50 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:  275 – 295 eV
  • Recommended Extended BE Range for Measuring Chemical State Spectrum:  270 – 370 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 C and 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 

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Gas Phase XPS or UPS Spectra
 
 
     
     
     
     
     
     
     
     
     
 
 
 

 

Chemical State Spectra from Literature
 

 

from Thermo Scientific Website

 

 

 

This spectrum does not reveal C (1s) of diamond

 

 

 

 

 

 

 

 

 

 

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