STRUCTURAL RELAXATION IN GLASS-TRANSITION OF CHALCOGENIDE AMORPHOUS-SEMICONDUCTORS

The structural relaxation in the glass transition of a-As2S3 and a-Se has been investigated with the heat capacity data obtained on differen tial scanning calorimetry experiments. The heat capacity curves were a nalyzed by the Moynihan formulation with a Kohlrausch-Williams-Watts r elaxation function, phi(t) similar to exp[-(t/tau)(beta)]. It has been found for a-As2S3 that the configurational constraints increase with annealing so that the structural relaxation becomes more cooperative. The observation can be readily understood in terms of the energy lands cape with a hierarchical distribution of energy barriers. An increase in the non-exponentiality, beta, was observed when silver was doped in a-As2S3 up to 1.3 at.% acid when arsenic was doped in a-Se. The resul ts suggest that the thermokinetic structure changes gradually from a s tringy or ramified structure to a higher dimensional one and cooperati vely-rearranging regions become more compact with Ag-doping in a-As2S3 and As-doping in a-Se.