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

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Calcium (Ca)

 

Calcite – CaCO3	Calcium Metal – Cao	Selenite – CaSO4-2H2O

 

Page Index
Pure Element Spectra with Peak-fits IMFP and Cross-sections for Pure Element Native Oxide Spectra with Peak-fits Pure Oxide Spectra with Peak-fits	Valence Band Spectra Six (6) Tables of Chemical State BEs Histograms of NIST BEs Advanced XPS Information Section	Peak-fits and Overlays of Rb Chemical Compounds	Auger Peaks and Spectra Contamination XPS Facts, Guidance, Information Chemical State Spectra from Literature

• Expert Knowledge & Explanations

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Calcium (Ca^o) Metal

Peak-fits, BEs, FWHMs, and Peak Labels

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Calcium Metal (Cao) Ca (2p) Spectrum – raw Ion etched clean Flood Gun OFF – conductive metal	Calcium Metal (Cao) Peak-fit of Ca (2p) Spectrum Ion etched clean Flood Gun OFF – conductive metal
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Calcium Metal (Cao) Ca (2p) full range  – raw Ion etched clean Flood Gun OFF – conductive metal	Calcium Metal (Cao) Ca (2p) Spectrum – peak-fit no asymmetry Ion etched clean Flood Gun OFF – conductive metal
Survey Spectrum of Calcium (Cao) Metal with Peaks Integrated, Assigned and Labelled
→  Periodic Table   XPS Signals for Calcium, (Cao) Metal Spin-Orbit Term,  BE (eV) Value, and Scofield σ for Calcium 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   Ca (2s) 442 2.59 36.0   Ca (2p1/2) 350.05 1.72 38.4 Mg (Auger) overlaps Ca (2p3/2) 346.31 3.35 38.4   Ca (3s ) 44 0.351 46.6 O (2s) overlaps Ca (3p) 25 0.507 47.1 σ:  abbreviation for the term Scofield Photoionization Cross-Section which are used with IMFP and TF to produce RSFs and atom% quantitation Plasmon Peaks Energy Loss Peaks Auger Peaks Energy Loss Peak for Compounds:  ~xx eV above each peak max Intrinsic Bulk Plasmon Peaks:  ~x eV steps Expected Bandgap for CaF2: ~6-8 eV    *Scofield Cross-Section (σ) for C (1s) = 1.0 →  Periodic Table
Plasmon Peaks from Cao Metal Fresh exposed bulk produced by extensive Ar+ ion etching

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Ca (2p) – Extended Range Spectrum	Ca (2p) – Extended Range Spectrum – Vertically Expanded

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Ca (KLL) Auger Peaks from Ca^o Metal
Fresh exposed bulk produced by extensive Ar+ ion etching

Cao Metal – High BE Auger peaks	Cao Metal – full range BE Auger peaks
	na

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Side-by-Side Comparison of
Calcium, Ca^o and Calcium Halides
Peak-fits, BEs, FWHMs, and Peak Labels

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Pure Metal, Cao	Calcium Fluoride, CaF2
Ca (2p) from Calcium metal – peak-fit Ion Etched	Peak-fit of Ca (2p) from CaF2, Natural crystal freshly cleaved in lab air Charge Referenced to 285.0 eV

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Calcium Fluoride, CaF2 Peak-fit of Ca (2p) from CaF2, Natural crystal freshly cleaved in lab air Charge Referenced to 285.0 eV	Calcium Chloride, CaCl2 Peak-fit of Ca (2p) from CaCl2, xtal freshly cleaved in lab air Charge Referenced to 285.0 eV

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Calcium Bromide, CaBr2 Peak-fit of Ca (2p) from CaBr2, xtal freshly cleaved in lab air Charge Referenced to 285.0 eV	Calcium Iodide, CaI2 Peak-fit of Ca (2p) from CaI2 xtal freshly cleaved in lab air Charge Referenced to 285.0 eV

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Overlay of Ca (2p) Peak
from Ca^o Metal, CaI₂, and CaF₂

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Overlay of Ca (2p) Peak
from CaF₂, CaCl₂, CaBr₂, and CaI₂

 

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Survey Spectrum of Calcium Fluoride, CaF₂
with Peaks Integrated, Assigned and Labelled

 

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Survey Spectrum of Calcium Chloride, CaCl₂
with Peaks Integrated, Assigned and Labelled

 

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Survey Spectrum of Calcium Bromide, CaBr₂
with Peaks Integrated, Assigned and Labelled

 

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Survey Spectrum of Calcium Iodide, CaI₂
with Peaks Integrated, Assigned and Labelled

 

 

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Overlay of C (1s) Spectra from
CaCO₃ (Calcite) & CaMg(CO₃)₂ (Dolomite) crystals

Calcium Carbonate, CaCO3 Peak-fit of C (1s) from CaCO3, Calcite natural crystal cleaved in lab air Charge Referenced to 285.0 eV	Calcium Magnesium Carbonate, CaMg(CO3)2 Peak-fit of C (1s) from CaMg(CO3)2, Dolomite natural crystal cleaved in lab air Charge Referenced to 285.0 eV
Overlay of C (1s) Spectra from CaCO3 and CaMg(CO3)2
Overlay of Ca (2p) Spectra from CaCO3 (Calcite) & CaMg(CO3)2 (Dolomite) crystals
Calcium Carbonate, CaCO3 Peak-fit of Ca (2p) from CaCO3, Calcite natural crystal cleaved in lab air Charge Referenced to 285.0 eV	Calcium Magnesium Carbonate, CaMg(CO3)2 Peak-fit of Ca (2p) from CaMg(CO3)2, Dolomite natural crystal cleaved in lab air Charge Referenced to 285.0 eV
Overlay of Ca (2p) Spectra from CaCO3 and CaMg(CO3)2
This overlay assumes that hydrocarbon C (1s) at 285.0 eV is correct.	This overlay uses the Ca (2p3/2) peak at 347.8 eV for both CaCO3 and CaMg(CO3)2.  The difference is due to the presence of Mg Auger peaks.

Features Observed

• xx
• xx
• xx

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→  Periodic Table 

Valence Band Spectra

CaF₂, CaCl₂, CaBr₂, CaI₂

CaF2 Valence Band Spectrum	CaCl2 Valence Band Spectrum
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CaBr2 Valence Band Spectrum	CaI2 Valence Band Spectrum
Overlay of Valence Spectra from CaF2, CaCl2, CaBr2 and CaI2

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Valence Band Spectra

CaCO₃ and CaMg(CO₃)₂

CaCO3 (Calcite) Valence Band Spectrum	CaMg(CO3)2 (Dolomite) Valence Band Spectrum
	.
Overlay of Valence Spectra from CaCO3 and CaMg(CO3)2

 

Copyright ©:  The XPS Library

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Calcium Minerals, Gemstones, and Chemical Compounds
Kutnohorite – CaMn(CO3)2	Dolomite – CaMg(CO3)2	Brenkite – Ca2(CO3)F2	Parisite = CaCe2(CO3)3F2

→  Periodic Table 

 

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Six (6) Chemical State Tables of Ca (2p) BEs

 

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

 

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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 (2p_3/2) 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 (2p_3/2) 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 

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Table #1

Ca (2p) 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 NIST BE	Hydrocarbon C (1s) BE	Source
Ca	20	Ca – element (N*1)	345.9 eV		284.8 eV	Avg BE – NIST
Ca	20	Ca – element	346.3 eV		285.0 eV	The XPS Library
Ca	20	Ca-TiO3	346.3 eV		285.0 eV	The XPS Library
Ca	20	Ca-CO3	346.4 eV		285.0 eV	The XPS Library
Ca	20	Ca-(OH)2 (N*1)	346.7 eV		284.8 eV	Avg BE – NIST
Ca	20	Ca-CO3 (N*4)	346.7 eV	347.0 eV	284.8 eV	Avg BE – NIST
Ca	20	Ca-O	347.1 eV		285.0 eV	The XPS Library
Ca	20	Ca-WO4	347.2 eV		285.0 eV	The XPS Library
Ca	20	Ca-Mg(CO3)2	347.8eV		285.0 eV	The XPS Library
Ca	20	Ca-F2 (N*2)	347.8 eV	347.9 eV	284.8 eV	Avg BE – NIST
Ca	20	Ca-F2	348.0 eV	348.3 eV	285.0 eV	The XPS Library
Ca	20	Ca-SO4	348.1 eV		285.0 eV	The XPS Library
Ca	20	Ca-Cl2	348.2 eV		285.0 eV	The XPS Library
Ca	20	Ca-Br2	348.2 eV		285.0 eV	The XPS Library
Ca	20	Ca-I2	348.3 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 (2p_3/2) BE = 932.62 eV and Au (4f_7/2) 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 

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Table #2

Ca (2p) Chemical State BEs from:  “PHI Handbook”

C (1s) BE = 284.8 eV

Copyright ©:  Ulvac-PHI

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Table #3

Ca (2p) Chemical State BEs from:  “Thermo-Scientific” Website

C (1s) BE = 284.8 eV

Chemical state	Binding energy,  Ca 2p (eV)
CaCO3	347.2
Ca3(PO4)2	347.4

Copyright ©:  Thermo Scientific website

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Table #4

Ca (2p) 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

 

Copyright ©:  Mark Beisinger

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Table #5

Ca (2p) 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 Ca 2p3/2 CaCrO4 346.3 ±0.3 346.0 ～ 346.6 Ca 2p3/2 Ca 346.4 ±0.5 345.9 ～ 346.9 Ca 2p3/2 CaS 346.5 ±0.3 346.2 ～ 346.8 Ca 2p3/2 CaO 346.5 ±0.4 346.1 ～ 346.9 Ca 2p3/2 CaCO3 346.9 ±0.4 346.5 ～ 347.3 Ca 2p3/2 Ca3Si3O9 347.0 ±0.3 346.7 ～ 347.3 Ca 2p3/2 CaMoO4 347.2 ±0.3 346.9 ～ 347.5 Ca 2p3/2 CaF2 347.8 ±0.3 347.5 ～ 348.1 Ca 2p3/2 CaSO4 348.0 ±0.3 347.7 ～ 348.3 Ca 2p3/2 CaCl2 348.3 ±0.4 347.9 ～ 348.6 Ca 2p3/2 Ca(NO3)2 348.7 ±0.3 348.4 ～ 349.0

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NIST Database of Ca (2p_3/2) 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.

 

 

 

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Advanced XPS Information Section

Spectra, BEs, Features, Guidance and Cautions  

for XPS Research Studies on Calcium Materials

 

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Expert Knowledge Explanations

 

Overlay reveals shift	Shake-up Example	Auger signal overlaps X

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XPS Spectra

from

Common Calcium Compounds

                           

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Calcium Sulfate, CaSO₄

Survey Spectrum from Calcium Sulfate, CaSO4 powder	Ca (2p) Chemical State Spectrum from Calcium Sulfate, CaSO4 powder
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C (1s) Chemical State Spectrum from Calcium Sulfate, CaSO4 powder	O (1s) Chemical State Spectrum from Calcium Sulfate, CaSO4 powder
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Valence Band Spectrum from Calcium Sulfate, CaSO4 powder	S (2p) Chemical State Spectrum from Calcium Sulfate, CaSO4 powder

 

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Calcium Titanate, CaTiO₃
crystal, freshly exposed bulk

Survey Spectrum from CaTiO3 (Perovskite)	Ca (2p) Chemical State Spectrum from CaTiO3 (Perovskite)
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Ti (2p) Chemical State Spectrum from CaTiO3 (Perovskite)	C (1s) Chemical State Spectrum from CaTiO3 (Perovskite)
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O (1s) Chemical State Spectrum from CaTiO3 (Perovskite)	Valence Band Spectrum from CaTiO3 (Perovskite)

le 

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Valence Band Spectra Comparison and Overlay
CaSO4,  CaTiO₃

CaSO4 – exposed bulk Bands Aligned	CaTiO3 – powder Bands Aligned
Valence Band Spectra Overlay of CaSO4 and CaTiO3

Features Observed

• xx
• xx
• xx

→  Periodic Table 

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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 CaF₂

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  

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XPS Facts, Guidance & Information

→  Periodic Table 

		Element		Calcium (Ca)
		Primary XPS peak used for Peak-fitting :		Ca (2p3/2)
		Spin-Orbit (S-O) splitting for Primary Peak:		Spin-Orbit splitting for Ca (2p) orbital is: 3.6 eV
		Binding Energy (BE) of Primary XPS  Signal:		346.4 eV
		Scofield Cross-Section (σ) Value:		Ca (2p3/2) = 3.35     Ca (2p1/2) = 1.75
		Conductivity:		Calcium Resistivity = xx CaCO3 Resistivity = xx
		Range of Ca (2p) Chemical State BEs:		345 -349 eV range   (Cao to CaF2)
		signals from other elements that overlap Ca (2p) Primary Peak:		xx
		Bulk Plasmons:		~
		Shake-up Peaks:		xx
		Multiplet Splitting Peaks:		not possible
		General Information about Calcium Compounds:		xx
		Cautions – Chemical Poison Warning		Flammable

Copyright ©:  The XPS Library 

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Information Useful for Peak-fitting Ca (2p)

• FWHM (eV) of Ca (2p_3/2) for Pure Calcium metal:  1.0 eV using 25 eV Pass Energy after ion etching and very fast data collection cycles
• FWHM (eV) of Ca (2p_3/2) for Calcium Halides:  1.5-1.8 eV using 50 eV Pass Energy  (before ion etching)
• Binding Energy (BE) of Primary signal used for Measuring Chemical State Spectra:  346.4 eV for Ca (2p) with +/- 0.2 uncertainty
• List of XPS Peaks that can Overlap Peak-fit results for Ca (2p):  xx

→  Periodic Table 

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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 (3d_5/2) FWHM (eV) = ~0.95 eV for PE 50 on Thermo K-Alpha
  • Ag (3d_5/2) FWHM (eV) = ~1.00 eV for PE 80 on Kratos Nova
  • Ag (3d_5/2) FWHM (eV) = ~0.95 eV for PE 45 on PHI VersaProbe
  • Ag (3d_5/2) 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 Metal Oxide:  Pure element FWHM << Metal 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 metal or a conductive compound.
• Typical Peak-Shape:  80% G: 20% L,   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 

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Contaminants Specific to Calcium Metal

• Calcium metal develops a Native oxide that is usually 8-9 nm thick.  .
• With heat the Native oxide becomes thicker and the BE of the oxide shifts to higher BE
• Calcium does not readily form a 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 metals that readily oxidize in the air.
• High levels of Carbonate appear on reactive metal 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 (SO) BE of the hydroxide (water) contamination normally appears 0.5 to 1.0 eV above the oxide peak
• Calcium (Ca), 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 metals.  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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Data Collection Guidance

• Chemical state differentiation can be difficult
• 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 

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Data Collection Settings for Ca (2p)

• Conductivity:  Metal readily develops a native oxide that is sensitive to Flood Gun – Differential Charging Possible – float sample recommended
• Primary Peak (XPS Signal) used to measure Chemical State Spectra:  Ba (3d_5/2) at 780 eV
• Recommended Pass Energy for Measuring Chemical State Spectrum: 50-90 eV    (Produces Ag (3d_5/2) 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 

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Effects of Argon Ion Etching

• Carbides can appear after ion etching various reactive metals.  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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