Extended study into the prominence of aluminum content in controlling optical parameters, thermal properties, electrical conductivity and dielectric behavior of amorphous Al-Se-Te thin films for optoelectronic applications

Abstract

In the initial step of the current work’s scenarios, the AlxSe70Te30-x (x = 0, 15, and 30 wt.%Al) chalcogenide glasses were synthesized. The alloy-derived thin films with a thickness (∼200 nm) were prepared. The optical spectra (transmittance T(λ) and reflectance R(λ)) were measured in the range of (300–2500 nm). Calculation of the optical parameters included determining the energy bandgap, Eg and tail energy, Ee. The results revealed a decrease in the bandgap energy of the direct transition and an increase in the tail energy with increasing Al-content. The X-ray dispersive analysis (EDX) detected the presence of the elemental components in the three studied systems. As well, by analyzing X-ray diffraction patterns (XRD) and s canning electron microscopy (SEM), the amorphous state of the films was confirmed. In addition, differential scanning calorimetry (DSC) at a heating rate of 5 K/min was used to determine the pre-crystallization and crystallization parameters. For the study of DC conductivity, the temperat ure dependence of sheet resistance was measured and its related parameters were extracted. While, the study of AC conductivity began by measuring the temperature dependence of capacitance and conductance at 5 kHz. Electrical conductivity has been studied in a temperature range of (300–500 K). It was found that there are two types of conduction pathways. The activation energies, Mott parameters, barrier potential energy, and density of localized states around the Fermi level were all evaluated using Mott's variable range hopping model as a benchmark. The dielectric constant, loss factor, complicated electrical modules, and impedance spectroscopy parameters were all shown to be substantially dependent on temperature and Al-content.