Laser ablation sampling for induction coupled plasma source quadrupole mass spectrometry of Cd-Zn-Te materials

Abstract

A method to measure the elemental composition of both major and minor species that is spatially resolved along and below the surface of Cd-Zn-Te (CZT) crystal specimens is described. This method uses laser ablation sampling (LAS) for material introduction into an inductively coupled plasma (ICP) source quadrupole mass spectrometer (QMS) system for subsequent elemental analysis. Mass spectra are acquired at discrete locations on the surface of each CZT specimen, mounted inside a LAS cell. This cell allows argon sweep gas to transport the ablation products into the ICP-QMS for analysis. Since three component movement of the CZT specimen surface relative to the LAS site is possible under computer control, elemental analysis at specific locations on the surface can be obtained. Additional mass spectra are obtained by repetitive LAS at progressively deeper locations beneath the surface at a fixed position, and at difference sites of interest anywhere on the surface of the CZT specimen. These spectra are analyzed to obtain the relative ionic abundances of all detectable isotopes of the major (CZT matrix) and the minor (trace) elements. From these data, the ensemble atom mass concentrations are calculated for each LAS procedure. The relative mass fraction of each element specie within a particular LAS data set is then determined by calculating the ratio of its abundance to the whole ensemble mass in that sample.