1、BRITISH STANDARD BS ISO 21270:2004 Surface chemical analysis X-ray photoelectron and Auger electron spectrometers Linearity of intensity scale ICS 71.040.40 BS ISO 21270:2004 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 March 2005 BSI 3
2、1 March 2005 ISBN 0 580 45708 7 National foreword This British Standard reproduces verbatim ISO 21270:2004 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee CII/60, Surface chemical analysis, which has the responsibility to: A
3、 list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Corre
4、spondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not
5、of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European development
6、s and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages 1 to 13 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments
7、 issued since publication Amd. No. Date Comments Reference number ISO 21270:2004(E) OSI 4002INTERNATIONAL STANDARD ISO 21270 First edition 2004-06-01 Surface chemical analysis X-ray photoelectron and Auger electron spectrometers Linearity of intensity scale Analyse chimique des surfaces Spectromtres
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13、4002 Allr ithgsr esedevrBSISO21270:2004IS:07212 O4002(E) I SO 4002 All irthgs ersedevr iiiContents Page Foreword iv Introduction v 1 Scope 1 2 Normative reference . 1 3 Symbols . 1 4 Outline of the methods. 2 5 When to use this International Standard 2 6 Procedure for evaluating the intensity linear
14、ity 2 6.1 The samples 2 6.2 Preparing the copper sample 3 6.3 Preparing the stainless-steel sample or sample holder . 3 6.4 Choosing the spectrometer settings for which the intensity linearity measurement is required 3 6.5 Operating the instrument . 3 6.6 Measurement of the intensity scale linearity
15、 by varying the source flux . 4 6.7 Determination of the intensity scale linearity by varying the source flux 4 6.8 Measurement of the intensity scale linearity in XPS using the spectrum ratio method for systems with two or more but less than 30 X-ray source emission current settings . 6 6.9 Determi
16、nation of the intensity scale linearity in XPS using the spectrum ratio method for systems with two or more but less than 30 X-ray source emission current settings . 7 6.10 Completing the analysis. 9 Annex A (informative) Example results of linearity measurements using the spectrum ratio method (the
17、 second method). 10 Bibliography . 13 BSISO21270:2004IS:07212 O4002(E) iv I SO 4002 All irthgs ersedevrForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normal
18、ly carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the
19、 work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare I
20、nternational Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication 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 o
21、f 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 rights. ISO 21270 was prepared by Technical Committee ISO/TC 201, Surface chemical analysis, Subcommittee SC 7, X-ray photoelectron spectroscopy. BSISO21270:2
22、004IS:07212 O4002(E) I SO 4002 All irthgs ersedevr vIntroduction Quantitative analysis of materials at surfaces by Auger electron spectroscopy (AES) or X-ray photoelectron spectroscopy (XPS), requires measurements of the spectral intensities. Non-linearities in the respective instrument intensity sc
23、ales, unless corrected, lead directly to errors in the amounts of material determined. In general, intensity scales are linear at very low count rates but become progressively non-linear as the count rates rise. Measurements of intensity rely on the measurement system delivering an intensity signal
24、which is fixed in proportion to the intensity being measured. In counting systems, this proportionality is expected to be unity. If this proportionality varies with the signal level or counting rate, the measurement system is said to be non-linear. It is rare for non-linearities below 1 % to be trea
25、ted as significant. The intensity scale non-linearity may exceed 1 % for count rates which exceed 5 % of the maximum permissible count rate1,2 . For many instruments, the non-linearity behaviour will not vary significantly from month to month, provided the detection system is correctly set. For thes
26、e instruments, the count rate may be corrected, using the relevant relationship, so that the corrected intensity is then linear for a greatly extended fraction of the maximum obtainable count rate. In this International Standard, two simple relationships are described, involving a parameter known as
27、 the detector system dead time, to make this correction. For some instruments, the non-linearity may not be predictable or described by any simple relationship. For these instruments, this International Standard allows the extent of the non-linearity to be measured and a maximum count rate for an ac
28、ceptable limit of divergence from linearity to be defined. This limit of divergence from linearity is set by the user appropriately for the analyses to be conducted. In this International Standard, two methods for measuring the linearity are provided. The first is based on the principle that the spe
29、ctrometer output is proportional to the electron beam current in AES or the X-ray beam flux in XPS1 . This is the simplest method and may be conducted in instruments where the beam current or flux may be set at 30 or more approximately evenly spaced intervals up to the level required to generate the
30、 maximum count rate for which this International Standard is to be used. In some XPS instruments, this is not possible and the X-ray flux may only be set at one of two or more (but less than 30) pre-defined levels. For these instruments, the first method cannot be realized and a second method is giv
31、en2 . This International Standard should be used when characterising a new spectrometer so that it may be operated in an appropriate count rate range. It is repeated after any substantive modification to the detection circuits, or after the multiplier voltage has been increased (since the previous t
32、est with this International Standard) by one-third of the range of increase provided by the manufacturer, or after replacement of the electron multiplier(s) or at intervals of approximately 12 months. BSISO21270:2004blank 4002:07212OSISBINTENRATIONAL TSANDADR IS:07212 O4002(E)I SO 4002 All irthgs er
33、sedevr 1Surface chemical analysis X-ray photoelectron and Auger electron spectrometers Linearity of intensity scale 1 Scope This International Standard specifies two methods for determining the maximum count rate for an acceptable limit of divergence from linearity of the intensity scale of Auger an
34、d X-ray photoelectron spectrometers. It also includes methods to correct for intensity non-linearities so that a higher maximum count rate can be employed for those spectrometers for which the relevant correction equations have been shown to be valid. 2 Normative reference The following referenced d
35、ocuments 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 Vocabulary 3 Symbols E Cumeasured ener
36、gy value for the Cu L 3 VV peak E jenergy value for the jth energy channel I imeasure of the ith flux value of beam current in AES or X-ray anode emission current in XPS k a constant M H (E j ) corrected count rate for the high-intensity X-ray spectrum at energy E jM icorrected count rate for the it
37、h flux value M L (E j ) corrected count rate for the low-intensity X-ray spectrum at energy E jN H (E j ) measured count rate for the high-intensity X-ray spectrum at energy E jN imeasured count rate for the ith flux value N L (E j ) measured count rate for the low-intensity X-ray spectrum at energy
38、 E jN maxmaximum count rate for which the system is to be used and for which the system remains within the acceptable limits of divergence from linearity given by k(1 ) fractional limits to the linearity eextended dead time nnon-extended dead time BSISO21270:2004IS:07212 O4002(E) 2 I SO 4002 All irt
39、hgs ersedevr4 Outline of the methods Two methods are available to evaluate the instrument intensity linearity. For AES instruments, and for XPS instruments in which 30 or more approximately evenly spaced and known increments in the X-ray flux are available, a general method is described. This is cal
40、led the method of varying the source flux. For XPS instruments with two or more but less than 30 settings available for the X-ray flux, this is not possible and a second method is given. This second method is called the spectrum ratio method. In the first method, the spectrometer must be fitted with
41、 an inert gas ion sputtering gun for cleaning samples. The intensity scale linearity measurements are then conducted using a sputter cleaned pure copper sample. In the second method, this sample or, if there is no ion gun, a stainless steel sample or sample holder is used. The selection of these sam
42、ples is described in 6.1 and their preparation in 6.2 and 6.3. Next, the spectrometer settings are selected in 6.4 and the instrument operated as described in 6.5. In the first method, described in 6.6, the spectrometer is set to detect the count rate at the Cu L 3 VV Auger electron peak. That count
43、 rate is then determined as a function of the electron beam current or as a function of the X-ray flux for 30 or more approximately evenly spaced increments in the X-ray flux. From these data, as described in 6.7, a plot of the quotient of the measured count rate and the beam current in AES, or of t
44、he quotient of the measured count rate and the X-ray flux in XPS, versus the measured count rate allows the linearity range and any relevant correction to be determined. In the second method, described in 6.8 and to be used for those XPS instruments in which 30 settable values of X-ray flux are not
45、available, widescan spectra are recorded for a high and a low X-ray source emission current. From these data, as described in 6.9, a plot of the quotient of the count rates of these two spectra, for each energy channel, versus the count rate for that channel in the high emission current spectrum, al
46、lows the linearity range and any relevant correction to the count rates to be determined. Finally, 6.10 summarizes the data to be recorded. 5 When to use this International Standard This International Standard shall be used when characterising a new spectrometer so that it may be operated in an appr
47、opriate count rate range. It shall then be repeated after any substantive modification to the detection circuits, after the multiplier voltage has been increased by one third of the range of increase (since the previous test with this standard) provided by the manufacturer, after replacement of the
48、electron multiplier(s) or at intervals of approximately 12 months. 6 Procedure for evaluating the intensity linearity 6.1 The samples For the method of varying the source flux, AES or XPS instruments may be used if they incorporate an inert gas ion gun for cleaning samples. For this method, use a po
49、lycrystalline Cu sample of at least 99,8 % purity and proceed to 6.2. The second method, the spectrum ratio method, is only applicable to XPS instruments. For this second method, either use a polycrystalline Cu sample of at least 99,8 % purity or a stainless-steel sample or sample holder. If the instrument does not incorporate an inert gas ion gun, the stainless-steel sample or sample holder shall be used. Proceed to 6.3. NOTE 1 For
