Physical evolution and topology of (As2Se3)(1-x)Tl-x alloys

Ternary compound As-Se-Tl amorphous films, have been deposited by thermal e vaporation with thickness in the range of 200 nm. The optical band gap was determined as a function of Tl addition, heat treatment and type of substra te. It was found to be in the range 0.6-1.72 eV. X-ray diffraction measurem ents were also carried out. Using simple consideration, based on coordination numbers (m) and bond ener gies, the average number of near-neighbors of each type expected to surroun d the atom has been estimated. These glasses assume simple additive bond en ergies. It was found that there is a correlation between the chalcogenide g lass forming ability and the number of lone pair electrons for a chalcogeni de system. Moreover, the briefly mentioned films are studied by the scannin g electron microscope. It is shown general grain growth phenomena occurs on the film free surface during the deposition process. The influence of the annealing time and the type of substrate on the surface morphology is demon strated. (C) 2001 Elsevier Science Ltd. All rights reserved.