ASTM_E_1505_-_92_2001.pdf

Designation:E 1505 92(Reapproved 2001)Standard Guide forDetermining SIMS Relative Sensitivity Factors from IonImplanted External Standards1This standard is issued under the fixed designation E 1505;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 The purpose of this guide is to provide the secondary ionmass spectrometry(SIMS)analyst with two procedures fordetermining relative sensitivity factors(RSFs)from ion im-planted external standards.This guide may be used for obtain-ing the RSFs of trace elements(1 atomic%).In addition,this guidedoes not describe procedures for obtaining RSFs from implantsin heterogeneous(either laterally or in-depth)specimens.1.3 The values stated in SI units are to be regarded as thestandard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:E 673 Terminology Relating to Surface Analysis23.Terminology3.1 DefinitionsSee Terminology E 673 for definitions ofterms used in SIMS.4.Summary of Practice4.1 This guide will allow calculation of the RSFs of traceelements from plots of SIMS secondary ion intensity(counts/s)versus time(s)that are acquired during the sputtering of ionimplanted external standards.Briefly,these plots are obtainedin the following manner:an ion beam of a particular ionspecies,ion energy,and angle of incidence is used to bombardan ion implanted external standard.The beam is rastered ordefocussed in order to attempt to produce uniform currentdensity in the analyzed area,which is defined by means ofmechanical or electronic gating.The intensities of the second-ary ions associated with the implanted element of interest anda reference element(typically,a major element in the specimenmatrix,which is distributed homogeneously in the specimen ata known concentration)are monitored with respect to timeduring the ion sputtering.4.2 An RSF for a given analyte ion,A,and a given referenceion,R,is equal to the ratio of their respective useful ion yields,tAtR1,where t equals the number of ions detected divided bythe number of corresponding atoms sputtered(1-3).3An RSF isdetermined from the secondary ion intensity versus time dataobtained from implanted standards using one of two arithmeticmodels described in the procedure(Section 7)of this guide.Ameasure of final crater depth is required for RSF determination.This measurement may be performed by another analyticaltechnique(see Section 7).5.Significance and Use5.1 The quantification of trace element compositions inhomogeneous matrices from first principles requires(1)knowl-edge of the factors influencing ion and sputtering yields and(2)understanding of how instrumental parameters influence theseyields(1-3).This information is difficult to obtain.Therefore,SIMS operators commonly use external standards to determineRSFs.These RSFs are then used to quantify the composition oftrace elements in the specimen of interest through the applica-tion of the following equation to each data point of the depthprofile of interest(1-3).CA5 IA CRIR RSF N!21(1)where:CAand CR=concentrations(atoms-cm3)of the analyteand reference elements,respectively;Iaand IR=intensities(counts/s)obtained from the ana-lyte and reference ions,respectively;andN=natural abundance(expressed as a fraction)of the analyte isotope being examined.5.2 The most common method of creating external stan-dards is to use an ion accelerator to homogeneously implant aknown dose of ions of a particular elemental isotope into aspecimen matrix that matches the specimen of interest(4).Theimplanted ion depth distribution is near-Gaussian(see Fig.1)1This guide is under the jurisdiction of ASTM Committee E42 on SurfaceAnalysis and is the direct responsibility of Subcommittee E42.06 on SIMS.Current edition approved Nov.15,1992.Published January 1993.2Annual Book of ASTM Standards,Vol 03.06.3The boldface numbers in parentheses refer to the list of references at the end ofthis guide.1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.and is therefore distinguished readily from background signalintensities.Elemental quantification performed using RSFsobtained from implant standards is generally accurate to 615%relative standard deviation(4-6).6.Apparatus6.1 The procedures described here can be used to determinean RSF from data obtained with virtually any SIMS instru-ment.6.2 The procedures described in this guide may be used toobtain RSFs from most implant standards in which the near-Gaussian implant distribution(see Fig.1)is observed clearlybeneath an