On the Changes in the Structural and Optical Properties Accompanying the Athermal Photovitrification Phenomenon in As50Se50 Thin Films

The effect of successive annealing illumination cycles on the structural and optical properties of wedge-shaped As50Se50 amorphous chalcogenide thin films, has been studied. It is observed that illumination increases the thickness and shrinks the bandgap. Annealing of the chalcogenide films, before or after illumination, decreases the thickness. However, although annealing after illumination increases the bandgap, when this treatment is carried out upon the as-evaporated films, the bandgap decreases. The photostructural changes have been explained in terms of two different mechanisms, which can coexist. One of them involving the repulsion and slip motion of the 2D structural layers comprising the pyramidal' network, as a consequence of the negative charging of these structural layers, by electron accumulation in conduction-band tails, and the other, involving the As4Se4 molecules, typical of thermally evaporated As-rich chalcogenides films, and forming particularly the crystalline form of medium-thickness (1+2 %m) AssoSe50 films.
Published in Jnl. of Optoelectronics and Advanced Materials, v3 n2, Jun 2001. p287-294 This article is from ADA398590 International Workshop on Amorphous and Nanostructured Chalcogenides 1st, Fundamentals and Applications held in Bucharest, Romania, 25-28 Jun 2001. Part 1