ASTM E1523-15

Standard Guide to Charge Control and Charge Referencing Techniques in X-Ray Photoelectron Spectroscopy

SIGNIFICANCE AND USE
5.1 The acquisition of chemical information from variations in the energy position of peaks in the XPS spectrum is of primary interest in the use of XPS as a surface analytical tool. Surface charging acts to shift spectral peaks independent of their chemical relationship to other elements on the same surface. The desire to eliminate the influence of surface charging on the peak positions and peak shapes has resulted in the development of several empirical methods designed to assist in the interpretation of the XPS peak positions, determine surface chemistry, and allow comparison of spectra of conducting and non-conducting systems of the same element. It is assumed that the spectrometer is generally working properly for non-insulating specimens (see Practice E902).  
5.2 Although highly reliable methods have now been developed to stabilize surface potentials during XPS analysis of most materials (5, 6), no single method has been developed to deal with surface charging in all circumstances (10, 11). For insulators, an appropriate choice of any control or referencing system will depend on the nature of the specimen, the instruments, and the information needed. The appropriate use of charge control and referencing techniques will result in more consistent, reproducible data. Researchers are strongly urged to report both the control and referencing techniques that have been used, the specific peaks and binding energies used as standards (if any), and the criteria applied in determining optimum results so that the appropriate comparisons may be made.
SCOPE
1.1 This guide acquaints the X-ray photoelectron spectroscopy (XPS) user with the various charge control and charge shift referencing techniques that are and have been used in the acquisition and interpretation of XPS data from surfaces of insulating specimens and provides information needed for reporting the methods used to customers or in the literature.  
1.2 This guide is intended to apply to charge control and charge referencing techniques in XPS and is not necessarily applicable to electron-excited systems.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Published
• Publication Date: 31-May-2015
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: E42 - Surface Analysis
• Drafting Committee: E42.03 - Auger Electron Spectroscopy and X-Ray Photoelectron Spectroscopy

Relations

• Referred By: ASTM E2108-16 - Standard Practice for Calibration of the Electron Binding-Energy Scale of an X-Ray Photoelectron Spectrometer
• Effective Date: 01-Jun-2015
• Referred By: ASTM E2735-14(2020) - Standard Guide for Selection of Calibrations Needed for X-ray Photoelectron Spectroscopy (XPS) Experiments
• Effective Date: 01-Jun-2015
• Referred By: ASTM E1078-14(2020) - Standard Guide for Specimen Preparation and Mounting in Surface Analysis
• Effective Date: 01-Jun-2015

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1523 − 15
Standard Guide to
Charge Control and Charge Referencing Techniques in
1
X-Ray Photoelectron Spectroscopy
This standard is issued under the fixed designation E1523; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
3.1 Definitions—See Terminology E673 for definitions of
1.1 This guide acquaints the X-ray photoelectron spectros-
copy (XPS) user with the various charge control and charge terms used in XPS.
shift referencing techniques that are and have been used in the
3.2 Symbols:
acquisition and interpretation of XPS data from surfaces of
BE Binding energy, in eV
insulating specimens and provides information needed for
BE Corrected binding energy, in eV
corr
BE Measured binding energy, in eV
reporting the methods used to customers or in the literature.
meas
BE Reference binding energy, in eV
ref
1.2 This guide is intended to apply to charge control and BE Measured Binding energy, in eV, of a reference line
meas, ref
FWHM Full width at half maximum amplitude of a peak in the
charge referencing techniques in XPS and is not necessarily
photoelectron spectrum above the background, in eV
applicable to electron-excited systems.
XPS X-ray photoelectron spectroscopy
∆ Correction energy, to be added to measured binding
corr
1.3 The values stated in SI units are to be regarded as
energies for charge correction, in eV
standard. No other units of measurement are included in this
standard.
4. Overview of Charging Effects
1.4 This standard does not purport to address all of the
4.1 For insulating specimen surfaces, the emission of pho-
safety concerns, if any, associated with its use. It is the
toelectrons following X-ray excitation may result in a tempo-
responsibility of the user of this standard to establish appro-
rary (or sometimes persistent) buildup of a positive surface
priate safety and health practices and determine the applica-
charge caused by the photoelectric effect. Its insulating nature
bility of regulatory limitations prior to use.
prevents the compensation of the charge buildup by means of
electron conduction from the sample holder. This positive
2. Referenced Documents surface charge changes the surface potential thereby shifting
2
the measured energies of the photoelectron peaks to higher
2.1 ASTM Standards:
binding energy. This binding energy shift may reach a nearly
E673 Terminology Relating to SurfaceAnalysis (Withdrawn
3
steady-state value of between 2 and 5 eV for spectrometers
2012)
equipped with nonmonochromatic X-ray sources. The surface
E902 Practice for Checking the Operating Characteristics of
3
potential charge and the resulting binding energy shift is,
X-Ray Photoelectron Spectrometers (Withdrawn 2011)
generally, larger for spectrometers equipped with monochro-
E1078 Guide for Specimen Preparation and Mounting in
matic X-ray sources because of the, generally, lower flux of
Surface Analysis
low-energy electrons impinging on the specimen surface. This
E1829 Guide for Handling Specimens Prior to Surface
lower flux arises because focused, monochromatic X-ray
Analysis
beams irradiate only a portion of the specimen and not other
nearby surfaces (for example, the specimen holder) that are
sources of low-energy electrons. The absence of an X-ray
1
This guide is under the jurisdiction of ASTM Committee E42 on Surface
window in many monochromatic X-ray sources (or a greater
Analysis and is the direct responsibility of Subcommittee E42.03 on Auger Electron
distance of the specimen from the X-ray window) also elimi-
Spectroscopy and X-Ray Photoelectron Spectroscopy.
nates another source of low-energy electrons.
Current edition approved June 1, 2015. Published June 2015. Originally
approved in 1993. Last previous edition approved in 2009 as E1523 – 09. DOI:
4.2 The amount of induced surface charge, its distribution
10.1520/E1523-15.
2
acrossthespecimensurface,anditsdependenceonexperimen-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
tal conditions are determined by several factors including
Standards volume information, refer to the standard’s Document Summary page on
specimen composition, homogeneity, magnitude of surface
the ASTM website.
3
conductivity, total photoionization cross-section, surface
The last approved version of this historical standard is referenced on
www.astm.org. topography, spa
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E1523 − 09 E1523 − 15
Standard Guide to
Charge Control and Charge Referencing Techniques in
1
X-Ray Photoelectron Spectroscopy
This standard is issued under the fixed designation E1523; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This guide acquaints the X-ray photoelectron spectroscopy (XPS) user with the various charge control and charge shift
referencing techniques that are and have been used in the acquisition and interpretation of XPS data from surfaces of insulating
specimens and provides information needed for reporting the methods used to customers or in the literature.
1.2 This guide is intended to apply to charge control and charge referencing techniques in XPS and is not necessarily applicable
to electron-excited systems.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
3
E673 Terminology Relating to Surface Analysis (Withdrawn 2012)
3
E902 Practice for Checking the Operating Characteristics of X-Ray Photoelectron Spectrometers (Withdrawn 2011)
E1078 Guide for Specimen Preparation and Mounting in Surface Analysis
E1829 Guide for Handling Specimens Prior to Surface Analysis
3. Terminology
3.1 Definitions—See Terminology E673 for definitions of terms used in XPS.
3.2 Symbols:
BE Binding energy, in eV
BE Corrected binding energy, in eV
corr
BE Measured binding energy, in eV
meas
BE Reference binding energy, in eV
ref
BE Measured Binding energy, in eV, of a reference line
meas, ref
FWHM Full width at half maximum amplitude of a peak in the
photoelectron spectrum above the background, in eV
XPS X-ray photoelectron spectroscopy
Δ Correction energy, to be added to measured binding
corr
energies for charge correction, in eV
4. Overview of Charging Effects
4.1 For insulating specimen surfaces, the emission of photoelectrons following X-ray excitation may result in a temporary (or
sometimes persistent) buildup of a positive surface charge caused by the photoelectric effect. Its insulating nature prevents the
compensation of the charge buildup by means of electron conduction from the sample holder. This positive surface charge changes
the surface potential thereby shifting the measured energies of the photoelectron peaks to higher binding energy. This binding
1
This guide is under the jurisdiction of ASTM Committee E42 on Surface Analysis and is the direct responsibility of Subcommittee E42.03 on Auger Electron
Spectroscopy and X-Ray Photoelectron Spectroscopy.
Current edition approved May 1, 2009June 1, 2015. Published June 2009June 2015. Originally approved in 1993. Last previous edition approved in 20032009 as
E1523 – 03.E1523 – 09. DOI: 10.1520/E1523-09.10.1520/E1523-15.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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E1523 − 15
energy shift may reach a nearly steady-state value of between 2 and 5 eV for spectrometers equipped with nonmonochromatic
X-ray sources. The surface potential charge and the resulting binding energy shift is, generally, larger for spectrometers equipped
with monochromatic X-ray sources because of the, generally, lower flux of low-energy electrons impinging on the specimen
surface. This lower flux arises because focused, monochromatic X-ray beams irradiate only a portion of the specimen and not other
nearby surfaces (for example, the specimen holder) that are sources of low-energy electrons. The absence of an X-ray window in
many monochromatic X-ray sources (or a greater distance of the specimen from the X-ray window)
...