LASER INDUCED MICROCRYSTALLIZATION OF BULK AMORPHOUS Ge₁₅Se_85−xTe_x

Abstract

Bulk amorphous samples of Ge₁₅Se_85−xTe_x (x = 10,15,20,25) were prepared by a rapid quenching. X-ray diffraction analysis revealed that the as-grown samples were amorphous. In order to understand the laser induced changes, the samples were irradiated with Q-switched Nd: YAG laser pulses of various energy densities (2-50 mJ/cm²). These studies showed that low energy pulses (≤10 mJ/cm²) have no influence on the structure and the transport properties of the samples whereas energy pulses (≥ 10 mJ/cm²) resulted in microcrystallization of the samples. Electrical transport properties such as d.c. electrical conductivity and thermoelectric power were measured as a function of temperature (200 -350 K) and composition. Results were analysed in terms of Small polaron model and two carrier model respectively. The electrical conduction, interestingly, was observed as intrinsic in the entire temperature range of measurements for both as-grown and irradiated samples.