INFLUENCE OF TELLURIUM ON THE PROPERTIES OF MOSE2-XTEX TEXTURED THIN-FILMS

Textured MoSe2-xTex thin films obtained by d.c. diode sputtering and post-annealing (T = 840 K for 24 h) under selenium and tellurium pressure were characterized by transmission electron microscopy (TEM), Auger electron spectroscopy (AES), photoelectron spectroscopy, optical absorption and electrical resistivity measurements. It was found by TEM analysis that, for all x(0 less-than-or-equal-to x less-than-or-equal-to 0.15), the crystallites grow according to an MoSe2 hexagonal structure pattern with the interplanar spacings expected for MoSe2. An AES analysis on the basis of a resolution of 2-mu-m or less has revealed that tellurium was evenly distributed in the film. However, a microprobe-equipped scanning transmission electron microscope, when the electron beam is 5 nm diameter at the point of impact, reveals that the tellurium peak intensity varies from one analysed point to the other. Optical absorption, in the light of single-crystal absorption, is interpreted in terms of surface roughness of the samples and a strong absorption region of MoSe2 in the high energy domain (hv > 1.4 eV). The electrical conductivity is governed by grain boundary scattering mechanisms. The increase in the resistivity of the films after annealing (4 h, 723 K) under vacuum is explained by the escape of tellurium from the grain boundaries.