As-grown microcrystalline stoichiometric Sb40Te60 films were examined by heat-treatment and laser-irradiation experiments for their potential use in optical storage. Compositional, structural, and optical studies were carried out for films heat-treated at various temperatures in the range 0-260 degrees C. They revealed a stable phase (Sb60Te40) in the range 110-185 degrees C and a monotonic decrease of Te below and above this range. The irradiation experiment showed the possibility of both reversible and irreversible phase changes depending on the laser power. Comparing the two experiments, we believe the phase responsible for reversible changes is Sb100-xTex (x = 38-45). The irreversible changes were found to be due to large deviation in this stoichiometry.