Characterization of Ge-Bi-S glass by thermal, electrical, switching and optical measurements

A study of the synthesized Ge22.5Bi7S70.5 glassy system has been carried ou t. Differential thermal analysis data indicate the retention in the as-quen ched sample of two amorphous phases. Thermal conductivity, psi, measurement s on bulk sample reveal that the main contribution to psi is due to phonon thermal conductivity. Thermal evaporation of the synthesized ingot gives fi lms with Ge20.7Bi6.8S72.5 as composition. The values of the activation ener gy and the pre-exponential factor calculated from the direct current electr ical conductivity above 53 degrees C suggest that carrier conduction occurr ed between extended states in these films. The I-V characteristics in the o ff-state and the switching phenomenon are investigated. A memory switch wit h a threshold voltage decreasing with temperature is detected for the studi ed films. Optical parameters such as absorption coefficient, optical gap an d refractive index are also determined. Comparison with binary Ge-S glass r eveals that the addition of Bi introduces additional absorbing states at ba nd edges. (C) 1998 Kluwer Academic Publishers.