NPL has developed a number of reference materials and calibration software for quantitative chemical analysis of surfaces and depth profiling. Below are the answers to some questions that are regularly asked by potential and existing customers.

• Can one set of materials, either SCAA87 or SCAA90, be used with both the AES and XPS software?
  The SCAA87 and SCAA90 reference samples themselves are the same as each other, but when you buy the SCAA87 you are getting traceability for AES and likewise with the SCAA90 you have traceability for XPS calibration. Traceability is not just the material itself but its measurement context. XPS and AES both have their place as surface analysis techniques because they address different problems. If some issue of traceability arises (e.g. due to technique development or novel electron optics) in XPS, but is not numerically significant in AES, we may contact only SCAA90 purchasers to quote uncertainties for the new instrument type, for example. Similarly for AES. We do not anticipate ever having to do this, but it illustrates that you are not just buying metal, you are buying the assessment of that material for traceability and reference purposes for that technique. If you bear these issues in mind you may still wish to purchase just one set of material and use it for calibrating both techniques, you are quite at liberty to do so. Indeed you can use any material you deem suitable for calibrating your own instrument for the purpose you intend. If however you wish to quote the reference material as NPL's, you should buy the SCAA90 material for XPS and SCAA87 material for AES.
  
  
• Are the reference materials supplied with certificates?
  We do not send certificates for these materials as we supply them as "Reference Materials" and not "Certified Reference Materials". We buy the materials from external suppliers then cut and clean them. We then log each of the samples along with details of the recipient before selling them as SCAA87 or SCAA90 sets, this allows traceability when they are used in conjunction with our AES or XPS Calibration Software. When you buy the Reference Materials you are buying samples that we have determined to be suitable for traceability and reference purposes for either AES or XPS and if you then licence the software you can use them to produce traceable intensity calibrations. The certificates that the software produces then have to be signed by the "Technical Expert" for that piece of equipment to certify that the appropriate conditions and procedures have been used for that calibration.
  
  
• What purity are the reference materials?
  The material we buy is sold to us as the following purities Cu 99.90%, Ag 99.99+%, Au 99.99%.

If you cannot find the answer you are looking for, please contact nanoanalysis@npl.co.uk or fax+44 20 8943 6453.