Thickness dependence of the dielectric properties of thermally evaporated Sb₂Te₃ thin films

Sb₂Te₃ thin films of different thickness (23 – 350 nm) were prepared by thermal evaporation technique. The thickness dependence of the ac conductivity and dielectric properties of the Sb₂Te₃ films have been investigated in the frequency range 10 Hz- 100 kHz and within the temperature range 293-373K. Both the dielectric constant ₁ and dielectric loss factor ₂ were found to depend on frequency, temperature and film thickness. The frequency and temperature dependence of ac conductivity (σ_ac(ω)) has also been determined. The ac conductivity of our samples satisfies the well known ac power law; i.e., σ_ac(ω) ∝ ω^s where s<1 and independent of the film thickness. The temperature dependence of ac conductivity and parameter s is reasonably well interpreted by the correlated barrier hopping (CBH) model. The activation energies were evaluated for various thicknesses. The temperature coefficient of the capacitance (TCC) and permitivity (TCP) were determined as a function of the film thickness. The microstructure of the samples were analyzed using X-ray diffraction (XRD). This results are discussed on the base of the differences in their morphologies and thicknesses. The tendency for amorphization of the crystalline phases becomes evident as the film thickness increases.