1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 11938:2012Microbeam analysis Electron probe microanalysis Methods for elemental-mapping analysis using wavelength-dispersive spectroscopyBS ISO 11938:2012 BRITISH STANDARD
2、National forewordThis British Standard is the UK implementation of ISO 11938:2012The UK participation in its preparation was entrusted to TechnicalCommittee CII/9, Microbeam analysis.A list of organizations represented on this committee can beobtained on request to its secretary.This publication doe
3、s not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013 ISBN 978 0 580 63714 8 ICS 71.040.50 Compliance with a British Standard cannot confer immunity fromlega
4、l obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 30 April 2013. Amendments issued since publicationDate T e x t a f f e c t e dBS ISO 11938:2012 ISO 2012Microbeam analysis Electron probe microanalysis Methods for elemental-mapping
5、 analysis using wavelength-dispersive spectroscopyAnalyse par microfaisceaux Analyse par microsonde lectronique (microsonde de Castaing) Mthodes danalyse par cartographie lmentaire en utilisant la spectromtrie dispersion de longueur dondeINTERNATIONAL STANDARDISO11938First edition2012-03-01Reference
6、 numberISO 11938:2012(E)BS ISO 11938:2012ISO 11938:2012(E)ii ISO 2012 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including ph
7、otocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in Switzerl
8、andBS ISO 11938:2012ISO 11938:2012(E) ISO 2012 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope 12 Normative references . 13 Terms and definitions . 14 Procedure of mapping analysis . 24.1 General . 24.2 Specimen preparation 24.3 Measurement procedure . 35 Methods for displaying
9、element maps 65.1 General . 65.2 Raw X-ray intensity method . 65.3 k-value method . 65.4 Calibration curve method 65.5 Correlation method . 75.6 Matrix correction method 76 Evaluation of uncertainty 77 Report . 7Annex A (normative) Comparison of absorption effects for a light element 9Bibliography .
10、10BS ISO 11938:2012ISO 11938:2012(E)ForewordISO (the International Organization 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 in
11、terested 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 work. ISO collaborates closely with the International Electrotechni
12、cal 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 International Standards. Draft International Standards adopted by the t
13、echnical 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 of the elements of this document may be the subject of patent rights. IS
14、O shall not be held responsible for identifying any or all such patent rights.ISO 11938 was prepared by Technical Committee ISO/TC 202, Microbeam analysis, Subcommittee SC 2, Electron probe microanalysis.iv ISO 2012 All rights reservedBS ISO 11938:2012ISO 11938:2012(E)IntroductionElectron probe micr
15、oanalysis (EPMA) has been developed over the last 50 years1234and has many areas of application in science and industry. Both qualitative and accurate quantitative analyses are employed extensively in mineralogy and in metallurgical studies, for example. In recent years, with the advances in compute
16、rs, digital processing techniques have been developed and, instead of X-ray dot images being used to qualitatively observe element distributions, colour mapping techniques5are now often employed. These enable products to be compared and evaluated for the purpose of quality control. Particle analysis
17、 and/or phase analysis using mapping requires careful selection of the experimental parameters, and it is essential that a standard be available for this purpose in order to achieve consistent and reliable results. ISO 2012 All rights reserved vBS ISO 11938:2012BS ISO 11938:2012Microbeam analysis El
18、ectron probe microanalysis Methods for elemental-mapping analysis using wavelength-dispersive spectroscopy1 ScopeThis International Standard provides procedures for electron microprobe elemental-mapping analysis using wavelength-dispersive spectrometry. The choice between mapping with the electron b
19、eam moving digitally across the specimen (electron beam mapping) and mapping with stage movement only (large-area mapping) is assessed. It describes five types of data processing: the raw X-ray intensity data method, the k-value method, the calibration method, the correlation method and the matrix c
20、orrection method.2 Normative referencesThe 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 5725-6,
21、 Accuracy (trueness and precision) of measurement methods and results Part 6: Use in practice of accuracy valuesISO 14594, Microbeam analysis Electron probe microanalysis Guidelines for the determination of experimental parameters for wavelength dispersive spectroscopyISO 16592:2006, Microbeam analy
22、sis Electron probe microanalysis Guidelines for determining the carbon content of steels using a calibration curve methodISO/IEC 17025:2005, General requirements for the competence of testing and calibration laboratoriesISO 17470, Microbeam analysis Electron probe microanalysis Guidelines for qualit
23、ative point analysis by wavelength dispersive Xray spectrometryISO 22489, Microbeam analysis Electron probe microanalysis Quantitative point analysis for bulk specimens using wavelengthdispersive Xray spectroscopyISO 23833, Microbeam analysis Electron probe microanalysis (EPMA) Vocabulary3 Terms and
24、 definitionsFor the purposes of this document, the terms and definitions given in ISO 23833 and the following apply.3.1mapping areaorthogonal array of equally spaced pixels in the X and Y directions that define the region of the specimen being mappedNOTE Each pixel is analysed for the same time peri
25、od, and the integrity of the data from each pixel is maintained in the stored data such that the graphical display of the data exhibits the distribution for each of the elements analysed.3.2beam scanningtime-controlled movement of the electron beam on the specimen surface with the synchronized movem
26、ent on the display screenINTERNATIONAL STANDARD ISO 11938:2012(E) ISO 2012 All rights reserved 1BS ISO 11938:2012ISO 11938:2012(E)3.3pseudo-colour mapfalse-colour mapgrey-level mapelement concentration display using different grey levels or colours, where each pixel grey level or colour value repres
27、ents the magnitude of the measured element intensity at that pixel position3.4pixelsingle data point in a map3.5stage mappingproduction of an X-ray map by mechanically moving the stage under a stationary electron beam in a predefined orthogonal-array pattern4 Procedure of mapping analysis4.1 General
28、The experimental parameters to be used during the analysis should be selected using the guidelines detailed in ISO 14594.In order to carry out mapping analysis, the analysing instrument shall be sufficiently stable for any variation due to instrument drift over the total mapping period to be reasona
29、bly expected to be significantly less than the variation due to differences in the measured element intensities. The instruments stability will be defined from a test of the instruments performance. The stability should be measured over a time period similar to that used for the mapping analysis.NOT
30、E 1 An Si wafer is sufficiently homogeneous and suitable to check the stability.NOTE 2 There are two options for carrying out the background measurement. The first method is to measure both the peak and the background intensities pixel by pixel. This minimizes the effects of stage and/or beam energy
31、 drift, but requires the spectrometer to move between the peak and background positions at every pixel, significantly increasing analysis time and introducing potential drift in the spectrometer positioning. The second method is to acquire a complete peak map and a complete background map. This sign
32、ificantly reduces the total analysis time and removes the risk of spectrometer drift, but is more prone to stage and/or beam-energy drift.4.2 Specimen preparationThe specimen shall be prepared so as to minimize the effects of artefacts and errors on the mapping analysis, but without destroying the i
33、ntegrity of the specimen (see ISO 22489).The specimens (reference specimen and unknown specimen) shall be clean and free of dust.The specimen shall be as flat as possible. If necessary, the specimen shall be embedded in a mounting medium and metallographically polished.The specimen shall have good e
34、lectrical conductivity. Charging under electron beam irradiation can be avoided by coating the specimen with a conductive layer of a suitable material. The coating shall be as thin as possible whilst still providing sufficient charge dissipation. A conducting path shall be established between the sp
35、ecimen surface and the metallic specimen holder. Carbon coating is generally used but, in particular cases, other materials should be considered (Au, Al, etc.). Carbon to a thickness of around 10 nm to 20 nm is usually sufficient to establish good conduction. It is recommended that both the referenc
36、e material and unknown specimen be coated with the same element at the same thickness.2 ISO 2012 All rights reservedBS ISO 11938:2012ISO 11938:2012(E)4.3 Measurement procedure4.3.1 GeneralMapping analysis shall be performed as follows:a) Select the location and size of the required map area on the s
37、pecimen.b) Select the number of pixels to meet the required spatial resolution, and the method of acquisition (stage or beam mapping).c) Select and apply the element and instrument conditions.d) Collect characteristic peak and background X-rays and any required electron signals (e.g. backscatter, se
38、condary electrons, absorbed current) at each pixel, and store all data in the computer memory point by point1.e) Apply the chosen correction method to the X-ray data (see Clause 5).f) Finally, the data can be displayed as pseudo-colour maps, as shown in Figure 1.g) The mapping procedure is summarize
39、d in Figure 2.Figure 1 Procedure for converting mapping data into pseudo-colour mapsThe mapping area and resolution are selected on the specimen (grid A) and the mapping is acquired by electron beam movement or stage movement pixel by pixel (solid arrows above grid A). At each pixel position, x,y, t
40、he measured X-ray intensity, I, is converted via the chosen correction method, Fn(x,y,I), into a false-colour level at the correlating pixel position in the result map (grid B). ISO 2012 All rights reserved 3BS ISO 11938:2012ISO 11938:2012(E)Start Select map area:Locag415on, size, number of pixels,
41、beam or stage scanning. Select analysis condig415ons: Element X-ray lines, peak and background posig415onsa, spectrometer, counter type and diffracg415on crystals, accelerag415ng voltage, beam current, dwell g415mes. Collect data: Peak and background X-ray intensig415es, any required electron signal
42、s. Apply correcg415on method: Raw X-ray intensity method, k-value method, calibrag415on curve method, correlag415on method, matrix correcg415on method (see Clause 5).Display data aTo avoid the peak overlap problem, qualitative analysis is recommended (see ISO 17470).Figure 2 Flowchart for the mappin
43、g measurement procedure4.3.2 Probe conditionsThe accelerating voltage shall be selected so as to efficiently excite all the elements within the mapping area. For best resolution, the diameter of the excitation volume in the specimen shall be no greater than the pixel spacing.The probe current and dw
44、ell time shall be sufficient to provide a statistically meaningful X-ray peak intensity above that of the background for all the elements measured in the specimen. Beware that light-element and/or trace-element components might require higher count rates or longer counting times. The choice of beam
45、current and/or dwell time might also be limited for beam-sensitive materials, or by saturation of the X-ray detectors when measuring elements present in the specimen in high concentrations.4.3.3 Stage conditionsTo satisfy Braggs diffraction condition for detecting characteristic X-rays, the geometri
46、c relationship between the X-ray source, the analysing crystal and the X-ray detector shall be fixed. Therefore, the working distance (or optical focus) shall be kept constant.For stage mapping, the specimen surface shall be as flat as possible, in accordance with ISO 22489, and the specimen shall b
47、e installed horizontally in the specimen chamber to keep the surface always in optical focus. When the scanned area becomes larger, it might be difficult to maintain optical focus across the specimen. 4 ISO 2012 All rights reservedBS ISO 11938:2012ISO 11938:2012(E)With automation software, the Z pos
48、itions that correspond to the working distance can be determined as a function of the X and Y locations. This will ensure that optical focus is maintained for the entire map.4.3.4 Selection of scanning methodSince optimum X-ray emission is dependent upon the geometric relationship between the specim
49、en, the analysing crystal and the detector, defocussing will occur with electron beam mapping when the mapped area exceeds the region of optimum focus (see Figure 3). Beam mapping shall only be selected where there will be insignificant signal loss due to spectrometer defocussing over the entire mapped area. Otherwise, stage mapping shall be used.KeyX-axis distance, in micrometres, from focus in direction of beam scanningY-axis X-ray intensityFigure 3 Example of X-ray intensity drop by be
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