1、 Reference number ISO 19318:2004(E) ISO 2004INTERNATIONAL STANDARD ISO 19318 First edition 2004-05-01 Surface chemical analysis X-ray photoelectron spectroscopy Reporting of methods used for charge control and charge correction Analyse chimique des surfaces Spectroscopie de photolectrons Indication
2、des mthodes mises en oeuvre pour le contrle et la correction de la charge ISO 19318:2004(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are
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7、ts reservedISO 19318:2004(E) ISO 2004 All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope 1 2 Normative reference. 1 3 Terms and definitions. 1 4 Symbols and abbreviated terms 1 5 Apparatus. 2 6 Calibration of binding-energy scale 2 7 Reporting of information related to charge co
8、ntrol 2 7.1 Methods of charge control. 2 7.2 Information on specimen . 2 7.3 Instrument and operating conditions . 3 7.4 General method for charge control. 3 7.5 Reasons for needing charge control and for choosing the particular method for charge control 3 7.6 Values of experimental parameters 3 7.7
9、 Information on the effectiveness of the method of charge control . 4 8 Reporting of method(s) used for charge correction and the value of that correction. 4 8.1 Methods of charge correction . 4 8.2 Approach 4 8.3 Value of correction energy. 4 Annex A (informative) Description of methods of charge c
10、ontrol and charge correction 5 A.1 Introduction. 5 A.2 Methods of charge control. 5 A.3 Methods of charge correction . 7 A.4 Bias referencing17 . 8 A.5 Auger parameter measurements32-34 . 9 Bibliography . 10 ISO 19318:2004(E) iv ISO 2004 All rights reservedForeword ISO (the International Organizatio
11、n for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has
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14、ion as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent righ
15、ts. ISO 19318 was prepared by Technical Committee ISO/TC 201, Surface chemical analysis, Subcommittee SC 5, Auger electron spectroscopy. ISO 19318:2004(E) ISO 2004 All rights reserved vIntroduction X-ray photoelectron spectroscopy (XPS) is widely used for characterization of surfaces of materials. E
16、lements in the test specimen (with the exception of hydrogen and helium) are identified from comparisons of the binding energies of their core levels, determined from measured photoelectron spectra, with tabulations of these binding energies for the various elements. Information on the chemical stat
17、e of the detected elements can frequently be obtained from small variations (typically between 0,1 eV and 10 eV) of the core-level binding energies from the corresponding values for the pure elements. Reliable determination of chemical shifts often requires that the binding-energy scale of the XPS i
18、nstrument be calibrated with an uncertainty that could be as small as 0,1 eV. The surface potential of an insulating specimen will generally change during an XPS measurement due to surface charging, and it is then difficult to determine binding energies with the accuracy needed for elemental identif
19、ication or chemical-state determination. There are two steps in dealing with this problem. First, experimental steps can be taken to minimize the amount of surface charging (charge-control methods). Second, corrections for the effects of surface charging can be made after acquisition of the XPS data
20、 (charge- correction methods). Although the buildup of surface charge can complicate analysis in some circumstances, it can be creatively used as a tool to gain information about a specimen. The amount of induced charge near the surface, its distribution across the specimen surface, and its dependen
21、ce on experimental conditions are determined by many factors including those associated with the specimen and characteristics of the spectrometer. Charge buildup is a well-studied1, 2three-dimensional phenomenon that occurs along the specimen surface and into the material. Charge buildup may also oc
22、cur at phase boundaries or interface regions within the depth of the specimen that is irradiated by X-rays. Some specimens undergo time-dependent changes in the level of charging because of chemical changes or volatilization induced by photoelectrons and secondary electrons, X-rays, or heating. Such
23、 specimens may never achieve steady-state potentials. There is, at present, no universally applicable method or set of methods for charge control or for charge correction3, 4 . This International Standard specifies the information that shall be provided to document the method of charge control durin
24、g data acquisition and/or the method of charge correction during data analysis. Information is given in Annex A on common methods for charge control and charge correction that can be useful for many applications. The particular charge-control method that may be chosen in practice depends on the type
25、 of specimen (e.g., powder, thin film or thick specimen), the nature of the instrumentation, the size of the specimen, and the extent to which the specimen surface might be modified by a particular procedure. This International Standard is expected to have two main areas of application. First, it id
26、entifies information on methods of charge control and/or charge correction to be included in reports of XPS measurements (e.g., from an analyst to a customer or in publications) in order to evaluate, assess and reproduce data on insulating materials and to ensure that measurements on similar materia
27、ls can be meaningfully compared. Second, adherence to this International Standard will enable published binding energies to be used with confidence by other analysts and will lead to the inclusion of more reliable data in XPS databases. INTERNATIONAL STANDARD ISO 19318:2004(E) ISO 2004 All rights re
28、served 1Surface chemical analysis X-ray photoelectron spectroscopy Reporting of methods used for charge control and charge correction 1 Scope This International Standard specifies the minimum amount of information describing the methods of charge control and charge correction in measurements of core
29、-level binding energies for insulating specimens by X-ray photoelectron spectroscopy that shall be reported with the analytical results. Information is also provided on methods that have been found useful for charge control and for charge correction in the measurement of binding energies. 2 Normativ
30、e reference The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 18115, Surface chemical analysis
31、Vocabulary 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 18115 apply. 4 Symbols and abbreviated terms BE Binding energy, in eV BE corrCorrected binding energy, in eV BE measMeasured binding energy, in eV BE refReference binding energy, in eV FWHM F
32、ull width at half maximum amplitude of a peak in the photoelectron spectrum above the background, in eV XPS X-ray photoelectron spectroscopy corrCorrection energy, to be added to measured binding energies for charge correction, in eV ISO 19318:2004(E) 2 ISO 2004 All rights reserved5 Apparatus 5.1 On
33、e or more of the charge-control techniques mentioned in Clause A.2 may be employed in most XPS spectrometers. The XPS instrument shall be operated in accordance with the manufacturers or other documented procedures. 5.2 Some of the techniques outlined in Clause A.2 require special apparatus, such as
34、 an electron flood gun or a source for evaporative deposition of gold. 5.3 Certain specimen-mounting procedures, such as mounting the specimen under a fine metal mesh5 , can enhance electrical contact of the specimen with the specimen holder, or reduce the amount of surface charge buildup. This and
35、other methods of specimen mounting to reduce static charge are described in detail in ASTM E 1078 and ASTM E 18296, 7 . 6 Calibration of binding-energy scale The binding-energy scale of the X-ray photoelectron spectrometer shall be calibrated using ISO 154728or another documented method before appli
36、cation of this International Standard. 7 Reporting of information related to charge control 7.1 Methods of charge control Many of the methods commonly used to control the surface potential and to minimize surface charging are summarized in Clause A.2. Information on the following critical specimen a
37、nd experimental conditions shall be reported for individual specimens or collections of similar specimens. 7.2 Information on specimen 7.2.1 Specimen form The form of the specimen shall be reported. The physical nature, source, preparation method and specimen structure can influence charging behavio
38、ur2 . EXAMPLE 1 Powder EXAMPLE 2 Thin film spin-cast on silicon EXAMPLE 3 Macroscopic mineral specimen 7.2.2 Specimen dimensions The size and shape of a specimen can have a significant effect on the extent of specimen charging. The shape of the specimen shall be reported together with approximate va
39、lues of the dimensions of the specimen or of any relevant specimen features (e.g., particle diameters). 7.2.3 Specimen-mounting methods Specimen mounting and contact with the specimen holder can significantly impact charging1, 2 . The method by which a specimen is mounted, including information abou
40、t special methods used to increase conductivity or isolate a specimen from ground, shall be reported. EXAMPLE 1 Powder specimen pressed into foil, which was attached to specimen holder by tape EXAMPLE 2 1 ml of contaminated liquid deposited on a silicon substrate and dried prior to analysis ISO 1931
41、8:2004(E) ISO 2004 All rights reserved 3EXAMPLE 3 Specimen held to holder using conductive adhesive tape of a specified type EXAMPLE 4 Corroded specimen held on specimen holder by metal screw 7.2.4 Specimen treatment prior to or during analysis The specimen treatment prior to or during analysis incl
42、udes any physical or chemical treatment that can affect charging of the specimen during XPS measurements. NOTE Such treatment of the specimen may modify the surface composition as well as the electrical conductivity, and hence charging, of the surface region. 7.3 Instrument and operating conditions
43、The instrument operating conditions include details of the particular XPS instrument, the nature of the X-ray source, the approximate size of the X-ray beam on the specimen surface, the analyser pass energy, a measure of energy resolution such as the FWHM of the silver 3d 5/2photoelectron line for t
44、he selected operating conditions, the angle between the specimen normal and the X-ray source, and the use or not of a magnetic lens. 7.4 General method for charge control The particular instrumental component(s) used for charge control shall be identified. EXAMPLE 1 Electron flood gun EXAMPLE 2 Elec
45、tron flood gun in combination with an ion gun EXAMPLE 3 Specimen heating EXAMPLE 4 Irradiation with ultraviolet light If the components used are not standard for the XPS instrument, information shall be provided on the manufacturer or on the relevant design characteristics. 7.5 Reasons for needing c
46、harge control and for choosing the particular method for charge control The reasons for needing charge control and for choosing a particular method shall be reported. EXAMPLE 1 As supplied to us, the portion of the specimen of interest was isolated from ground. We supplied flood gun electrons for ch
47、arge compensation using the standard flood gun for this instrument. EXAMPLE 2 Experience with similar specimens indicated that differential charging was likely. To obtain good spectra, we totally isolated these specimens from ground. The application of the combined fluxes of a low-energy electron fl
48、ood gun and a low-energy ion flux produced well resolved peaks. EXAMPLE 3 Initial spectra without any charge control showed peak shifting and broadening. Placing a grounded fine grid above the specimen solved these problems without leading to a significant signal due to the grid material. This metho
49、d is easy to apply, and is used routinely in our measurements with similar specimens. 7.6 Values of experimental parameters Values of parameters used to control charge, such as flood gun settings, shall be reported. EXAMPLE For the flood gun, the cathode voltage was 5 V (with respect to instrumental ground), the emission current was 20 mA, and the gun cathode was 5 cm from the specimen. ISO 19318:2004(E) 4 ISO 2004 All rights reserved7.7 Information on the effectiveness of the method of charge control The adequacy
