Optical and electrical properties of Ge10+xSe40Te50−x thin film

Thin films with thickness 100 nm of Ge10+xSe40Te50−x (x ranging from 0.0 to 16.65 at.%) were formed by vacuum deposition at 1.33×10−4 Pa. The change in electrical resistivity of the films has been measured using coplanar method. The measurements have been carried out in a temperature range between 400 and 142 K. The values of the electrical activation energy lie in the range of 0.18–0.38 eV. The optical absorption behavior of these ternary thin films were studied from the reflection and transmission. The optical band gap was found to be in the range of 0.90–1.11 eV, and arose from indirect transitions. On the other hand, the width of the band tail Ee was found in the range 0.19–0.32 eV, and exhibits opposite behavior. This behavior is believed to be associated with a defected bond of TeTe and a cohesive energy (CE).