ELECTRON-STIMULATED DESORPTION OF THIN EPITAXIAL-FILMS OF KBR GROWN ON (100)INSB

We have measured time-of-flight (TOF) distributions of Br atoms desorb ed from thin (less than 1000 Angstrom) epitaxial films of KBr on (100) InSb with a 2 keV electron beam. Although the general structure of th e TOF spectra was similar to that obtained previously for the thick cr ystals, both the Fast and the slow (thermal) components of the distrib ution were strongly dependent on the film thickness. We argue that thi s dependence is due to two different diffusion processes involved in t he transport of the primary excitation products from the bulk to the s urface. By measuring the velocity resolved ESD yield for films of vari ous thicknesses, we determined that a diffusion length of the carriers responsible for the thermal ESD component varied from 30 to 700 Angst rom with temperature in the range 20-300 degrees C. In contrast, for t he non-thermal desorption we found the carrier diffusion length of abo ut 140 Angstrom which did not depend significantly on the temperature. (C) 1997 Elsevier Science B.V.