Abstract
Amorphous to crystalline phase transformations in thermally evaporated GeTe films have been analyzed by using the resistivityโtemperature curves and optical spectroscopic techniques. The phaseโtransition temperature increases slightly with annealing temperature, while a large change in the sheet resistance and appreciable decrease in the dc activation energy has been observed due to this transformation. The small value of sheet resistance for the crystalline films as compared to the amorphous ones above the transition temperature reveal the influence of the polarization near the metal/semiconductor interface forming the blocking layer at the interface toward the semiconductor side. The optical contrast value decreases with the decrease in wavelength due to the transitions from the deep levels below the valence band edge. The imaginary parts of dielectric function (ฮต~2~) have been calculated from the reflectivity data using the KramersโKronig transformations and exhibit its strong dependence on the annealing temperature. The optical gap and tailing parameter have also been studied with annealing temperature. These results have been explained on the basis of the structural relaxation or the change in the local structure due to amorphousโcrystalline transformation in the GeTe film due to thermal annealing.