STOICHIOMETRIC DEFECTS AND VOLUME DIFFUSION IN EPITAXIAL PBTE-SNTE MULTILAYERS

The effect of annealing on multilayer structures based on epitaxial layers of PbTe-SnTe was investigated by X-ray diffraction profile changes. Decrease of satellite reflections intensity and conversion of pattern asymmetry were found. Profiles of interplanar distance and electron density deviations were determined by solving both the direct problem (numerical computation of Takagi-Taupin equations) and the inverse problem (optimisation task) according to the average lattise model. Computation showed the presence of interlayer area of PbSnTe composition containing up to 8% of stoichiometric vacancy type defects between PbTe and SnTe layers. Two diffusion mechanisms are proposed: ''fast'' diffusion connected with occupation of stoichiometry defects and ''slow'' substitutional diffusion.