Thermal and optical properties of Ge5Bi18Se77 films

Amorphous films of Ge5Bi18Se77 deposited by vacuum evaporation have been st udied for their thermal and optical properties. Differential scanning calor imetry (DSC) has been used to perform the thermal analysis to estimate the activation energy for crystallization (E-c) and the order of crystallizatio n (m) of this material. The high value of E-c, 1.672 eV, indicates good sta bility of the amorphous phase. The optical constants of the as-deposited, a morphous and the thermally annealed crystalline films indicate semiconducti ng behavior and the band gap (E-g) determined from Tauc's plot are 0.92 eV and 0.8 eV for the amorphous and crystalline films, respectively. The value of the absorption coefficient (alpha) is of the order of 10(4) cm(-1) in t he optical range for both amorphous and crystalline films. The studies on o ptical and thermal properties confirm the suitability of these firms in pha se change optical recording.