The Development of Potential Thin Standards for Calibration of X-Ray Fluorescence Spectrometry

摘要

Thin films containing known concentrations of metals are important for the calibration of X-ray Fluorescence Spectrometry (XRF), especially for the analysis of collected airborne particulate matter. A focused ion-beam sputtering technique has been investigated as a candidate method for fabricating thin glass films containing know concentrations of metals on polycarbonate substrates. Glass targets were fabricated at NBS for these studies, and parameters such as ion-acceleration voltage and ion current were systematically varied to determine any changes in film composition. It was found that rather severe changes in instrumental parameters do not affect the elemental composition of the films appreciably. Up to eight substrates were coated at one time and the compositional reproducibility as measured by XRF for Si, Ca, Zn, and Pb for 13 samples was within five percent relative standard deviation at mass loadings of glass from 160 190 micrograms/cm. Glass films containing phosphorous and sulfur were also prepared to demonstrate the feasibility of preparing glass films containing such elements of low atomic number. Additional studies consisted of the deposition of finely ground synthetic glasses on membrane filters, and the characterization of some selected commercial thin films prepared by thermal evaporation.