Stoichiometry of various Ag(In)SbTe phase change materials (PCMs) determined using LA-ICP-MS

Abstract

In this study major element concentrations of AgInSbTe phase change materials of different stoichiometry were quantified using UV-ns-LA-ICP-MS. Performing raster ablation sampling, precision and accuracy of the determined concentrations were improved compared to single hole drilling ablation. Using raster mode, possible fractionation effects during the ablation and temporal mass load effects in the ICP were found less variable for the respective materials. Additionally, using raster mode a more representative sampling (mass) was achieved, which results in a more bulk-equivalent description of the sample. An indication for that is given by the improved RSD of the determined concentrations to values as low as 1%. A single calibration material composed of all four elements of interest was applied to determine the major element content in AgInSbTe samples with unknown stoichiometry. A quantification approach based on a 100% normalisation (see ref. 1) was used, due to the similar behaviour of the elements during raster ablation sampling. The high purity of these materials allows using the 100% normalisation, based on the four major elements only. Furthermore, the applicability of a four-component calibration material for the quantification of three-component AgSbTe materials was investigated in terms of precision and accuracy. The stoichiometry-dependent particle size distribution of the laser induced aerosol was studied and is suspected to be the limiting factor for accuracy. It is shown that a matrix-matched calibration material, or at least ablation conditions that provide a particle size-matched aerosol between calibration- and sample-material, provides access to accurate stoichiometry of such materials.