Glass transition temperature shift under pressure for some semiconducting glasses

Glass transition temperatures (T_g) were measured as a fucntion of pressure for the semiconducting glasses As₂S₃, Te₁₅Ge₂As₃ and Cd₆Ge₃As₁₁, using changes in the transit time of an ultrasonic pulse to detect the glass transition. The measurements of T_g as a function of pressure were compared to the predictions of the free volume theory of the glass transition. For As₂S₃ and Te₁₅Ge₂As₃, T_g first increased and then levelled off with increasing pressure, as predicted by the free volume theory. The amorphous semiconductor Cd₆Ge₃As₁₁ exhibited anomalous behavior: T_g first increased with pressure, but at the relatively low pressure of 1.5 kbar it began to decrease with increasing pressure.