Trace element standards for the electron microanalyser using layered and ion-implanted materials

Abstract

The merits and limitations of thin surface film deposition and ion implantation for preparing reference materials for quantitative analysis of trace elements using wavelength-dispersive X-ray spectrometry with the electron probe microanalyser are illustrated and discussed. The objective is to generate X-ray intensities typical of elements present at trace levels and to relate the measured intensities to the mass concentration of these elements when assumed to be homogeneously distributed within bulk materials. For this purpose, X-ray intensity calculations based on the use of analytical expressions for both the depth–ionization and the depth–concentration distributions, respectively, are presented. It will be demonstrated that gold-layered and materials ion implanted with gold can be advantageously used to validate the experimental approaches used for X-ray intensity measurements in the presence of distortions in the shape of an X-ray peak and the underlying continuous emission distribution, and also to test the algorithms and the physical parameters used in the analytical descriptions of the ionization and concentration profiles as a function of depth. The contribution of layered and ion-implanted compounds to a better understanding of surface and bulk charging phenomena in strongly insulating specimens is also presented.