1、BSI Standards PublicationBS ISO 17862:2013Surface chemical analysis Secondary ion massspectrometry Linearity ofintensity scale in single ioncounting time-of-flight massanalysersBS ISO 17862:2013 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 17862:2013.The UK
2、participation in its preparation was entrusted to TechnicalCommittee CII/60, Surface chemical analysis.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are re
3、sponsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 78684 6ICS 71.040.40Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandar
4、ds Policy and Strategy Committee on 31 December 2013.Amendments issued since publicationDate Text affectedBS ISO 17862:2013 ISO 2013Surface chemical analysis Secondary ion mass spectrometry Linearity of intensity scale in single ion counting time-of-flight mass analysersAnalyse chimique des surfaces
5、 Spectromtrie de masse des ions secondaires Linarit de lchelle dintensit des analyseurs de masse temps de vol pour comptage des ions individuelsINTERNATIONAL STANDARDISO17862First edition2013-12-15Reference numberISO 17862:2013(E)BS ISO 17862:2013ISO 17862:2013(E)ii ISO 2013 All rights reservedCOPYR
6、IGHT PROTECTED DOCUMENT ISO 2013All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permiss
7、ion. Permission can be requested 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 SwitzerlandBS ISO 17862:2013ISO
8、 17862:2013(E) ISO 2013 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Symbols and abbreviations . 12.1 Abbreviated terms . 12.2 Symbols . 13 Outline of method 24 Procedure for evaluating the intensity linearity 54.1 Obtaining the reference sample . 54.2 Preparation for mo
9、unting the sample . 54.3 Mounting the sample . 54.4 Operating the instrument 64.5 Acquiring the data 84.6 Checking the linearity 125 Interval for repeat measurements 17Annex A (normative) Computation of raster size, ion beam current, number of frames for analysis, and counts per pulse .18Annex B (no
10、rmative) Charge compensation setting .20Annex C (normative) Ion detector setting 21Annex D (informative) Instrumental factors affecting linearity .23Bibliography .25BS ISO 17862:2013ISO 17862:2013(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of nationa
11、l 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 the right to be represented on that committee. Internation
12、al organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended f
13、or its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.o
14、rg/directives).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 rights. Details of any patent rights identified during the development of the document will be
15、 in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions
16、related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe committee responsible for this document is ISO/TC 201, Surface chemical analysis, Subcommittee S
17、C 6, Secondary ion mass spectrometry.iv ISO 2013 All rights reservedBS ISO 17862:2013ISO 17862:2013(E)IntroductionFor the quantitative analysis of materials using secondary ion mass spectrometry (SIMS), measurements are made of the spectral intensities. Nonlinearity in the instrument intensity scale
18、, unless corrected, leads directly to errors in the relative amounts of material determined at surfaces and in depth profiles. In general, intensity scales are linear at very low count rates, or more correctly low counts per pulse, but become progressively nonlinear as the count rates rise. Measurem
19、ents of intensity rely on the measurement system delivering an intensity signal 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 sai
20、d to be nonlinear. It is rare for nonlinearities below 1 % to be treated as significant. The intensity scale nonlinearity can exceed 1 % for count rates that exceed 5 % of the maximum permissible count rate.1For many instruments, the nonlinearity behaviour will not vary significantly from month-to-m
21、onth, provided the detection system is correctly set. For these instruments, the count rate can 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. This correction to the intensity scale c
22、an or cannot already be available in the instruments data capture or processing computer. In this International Standard, a simple test of linearity is provided for the intensity lost in systems in which secondary ions arrive at a detector based on a microchannel plate or scintillator and photomulti
23、plier followed by a time-to-digital converter. If this test is shown to be valid, a correction is provided that, for suitable instruments, can extend the intensity scale by up to a factor of more than 50. For some instruments, the nonlinearity cannot be predictable nor described by any simple relati
24、onship. For these instruments, this International Standard allows the extent of the nonlinearity to be measured and a maximum count rate for an acceptable limit of divergence from linearity to be defined. In some cases, adjustments to the instrumental settings can improve the situation so that the r
25、equired correction is then valid. The limit of divergence from linearity is set by the user appropriately for the analyses to be conducted.Although there are a number of causes of nonlinearities in TOF-SIMS instrumentation, the most significant is intensity saturation caused by the effective dead-ti
26、me of the detector system. This arises since only one secondary ion count per primary ion pulse can be detected within a dead-time interval , regardless of the actual number of secondary ions arriving at the detector. Nonlinearity can also be exacerbated by unwanted background in the spectra.This In
27、ternational Standard provides, and can only provide, a correction to the dead-time nonlinearity for a somewhat ideal situation and not for all cases. Nevertheless, the significantly enhanced dynamic range or rate of working can be very important. Suggestions are included to optimize the instrument t
28、o provide the best measurement capability and to diagnose simple instrumental defects such as detector faults, e.g. a low detector efficiency or a detector not providing single ion counting. Then, a dead-time Poissonian correction is established to correct the measured counts within certain limits s
29、et by the analyst. This establishes an upper value for cM, the count per pulse, either before or after correction. This upper limit is generally applicable to peaks where the signal is constant with both time and spatial distribution, where there is only one peak within the dead-time interval, and w
30、here the background intensities are negligible (these conditions are not always satisfied in practice). This is explored and explained in detail in Reference 1. The results from applying this International Standard relate to a “best-case scenario” and the linearity achievable with Formula (1) can be
31、 lower in real cases where it is not practical to use a wide peak integration limit of the dead-time. More advanced dead-time correction routines should be sought in these cases and their effectiveness can be tested using the methodology here.This International Standard should be used when character
32、izing a new spectrometer so that it can be operated in an appropriate intensity range. It should then be repeated after any substantive modification to the detection circuits, after replacement of the microchannel plate (MCP), or at approximately six monthly intervals. ISO 2013 All rights reserved v
33、BS ISO 17862:2013BS ISO 17862:2013Surface chemical analysis Secondary ion mass spectrometry Linearity of intensity scale in single ion counting time-of-flight mass analysers1 ScopeThis International Standard specifies a method for determining the maximum count rate for an acceptable limit of diverge
34、nce from linearity of the intensity scale in single ion counting time-of-flight (TOF) secondary ion mass spectrometers using a test based on isotopic ratios in spectra from poly(tetrafluoroethylene) (PTFE). It also includes a method to correct for intensity nonlinearity arising from intensity lost f
35、rom a microchannel plate (MCP) or scintillator and photomultiplier followed by a time-to-digital converter (TDC) detection system caused by secondary ions arriving during its dead-time. The correction can increase the intensity range for 95 % linearity by a factor of up to more than 50 so that a hig
36、her maximum count rate can be employed for those spectrometers for which the relevant correction formulae have been shown to be valid. This International Standard can also be used to confirm the validity of instruments in which the dead-time correction is already made but in which further increases
37、can or cannot be possible.2 Symbols and abbreviations2.1 Abbreviated termsFor the purposes of this International Standard, the following abbreviations are used:MCP microchannel platePTFE poly(tetrafluoroethylene)SIMS secondary ion mass spectrometryTDC time-to-digital converterTOF time-of-flight2.2 S
38、ymbolsThe term intensity is used below and elsewhere. This refers to a measurement of peak area in the spectrum.cMmeasured counts per pulse intensitycPcorrected counts per pulse intensityFMshorthand for FM(i,j)FM(i,j) ratio of measured intensities for the ith 12CxFy+and 13C12Cx-1Fy+secondary ions in
39、 Table 1FPshorthand for FP(i,j)FP(i,j) ratio of corrected intensities for the ith 12CxFy+and 13C12Cx-1Fy+secondary ions in Table 1i index number for ion pair listed in Table 1INTERNATIONAL STANDARD ISO 17862:2013(E) ISO 2013 All rights reserved 1BS ISO 17862:2013ISO 17862:2013(E)imaxhighest primary
40、ion current used for the saturation analysisIMintegrated measured secondary ion intensity of a specified SIMS peakIM(X) integrated measured secondary ion intensity of the SIMS fragment XIPintegrated corrected secondary ion intensity of a specified SIMS peakIP(X) integrated corrected secondary ion in
41、tensity of the SIMS fragment Xj index number for spectrum in the measurement seriesk index number for setting the different primary ion currentsLPshorthand for LP(i,j)LP(i,j) ratio of FP(i,j) to the product (i) and (i)LMshorthand for LM(i,j)LM(i,j) ratio of FM(i,j) to the product (i) and (i)LMTtheor
42、etical ratio of measured and corrected intensities per pulsen number of raster frames used to generate each SIMS intensityN total number of primary pulses used to generate the SIMS spectrumR length of the raster side used to generate each SIMS intensityVEmass analyser desired energy acceptance, in e
43、VVRmass analyser reflector voltage referred to the sample potentialVTmass analyser reflector voltage referred to the sample potential for a secondary ion intensity to fall to half the maximum intensity(i) expected isotope ratio of the ith 12CxFy+and 13C12Cx-1Fy+secondary ions in Table 1(i) scaling f
44、actor to correct (i) for the measured data, found by fitting detection system dead-timex number of 13C or 12C atoms in the characteristic PTFE secondary iony number of F atoms in the characteristic PTFE secondary ion3 Outline of methodThe method is outlined by the flow chart shown in Figure 1. In th
45、is method, secondary ion spectra are measured for PTFE tape analysed in the “as received” condition with no in-house cleaning and no further sample preparation as described from 4.1 to 4.3. The analytical conditions are chosen by the analyst as described in 4.4 to provide secondary ion intensities p
46、er pulse in the linear and nonlinear ranges of detector ion counting. This is established using 16 test spectra for a test sample to define the correct range of primary ion beam current settings and 16 data spectra are then measured for the analysis sample to provide data for the linearity establish
47、ment. In order to ensure that the instrument is operating in the best condition for linearity, considerations for setting the ion beam, the mass analyser, the charge compensation, and the ion detection system are described from 4.5.2 to 4.5.5. PTFE is a bulk insulator and requires charge neutralizat
48、ion.2 ISO 2013 All rights reservedBS ISO 17862:2013ISO 17862:2013(E)The spectrometer should be operated under conditions that give the most stable performance. It is recommended that analysts use ISO 238302to confirm the repeatability of their instrument. The protocol described in this International
49、 Standard is closely aligned with that in ISO 23830 and those using that International Standard are already familiar with much of the procedure given here.The acquisition of data is described in 4.5 and details of the peaks to be measured are given in Table 1. The behaviour expected is described in 4.6 with relevant formulae. If the linearity is adequate, either for the data directly or for the data after correction using the instruments data capture computer, the work is complete until, through changes to the instrument o
