Effect of Annealing Temperature on the Electric and Dielectric Properties of Se_(70)Te_(15)Bi_(15) Films

摘要

The effect of annealing at different temperatures between T_g and T_c on the AC conductivity and dielectric properties was studied for Se_(70)Te_(15)Bi_(15) films grown by thermal evaporation technique. The films were characterized by X-ray diffraction, differential thermal analysis, and energy dispersive X-ray spectroscopy. X-ray diffraction analysis shows the occurrence of amorphous to polycrystalline transformation for films annealed at annealing temperature T_a ≥ 473 K. AC conductivity σ_(AC)(ω) was studied as a function of T_a, frequencies (0.1-100 kHz) and working temperatures (303-393 K). It was found that σ_(AC)(ω) obeyed Aω~s law. According to the values of s and its temperature dependence, the AC conduction mechanism was determined in terms of the correlated barrier hopping and quantum mechanical tunneling models for the as deposited and annealed films, respectively. The DC and AC activation energies were determined as a function of T_a. Values of dielectric constant ε_1 and dielectric loss ε_2 were found to increase with increasing T_a. A Debye-like relaxation of dielectric behavior was observed for polycrystalline films, and was found to be a thermally activated process.