Electrical and optical properties of thin film of a-Se 70Te 30 nanorods

Abstract

The electrical and optical properties of thin film of a-Se 70Te 30 nanorods are studied. Initially, the melt quenching technique is employed to prepare the glassy alloy of Se 70Te 30. X-ray diffraction technique is used to verify the amorphous nature of this alloy. The thin film of a-Se 70Te 30 is deposited on the glass substrate under an ambient gas (Ar) atmosphere using inert-gas consolidation (IGC) method. Transmission electron microscopy (TEM) is employed to study the microstructure of this film. It is found that the film contains nanorods of diameters varying from 30 to 80 nm and length of the order of few hundreds of nanometers. For electrical properties, the temperature dependence of dc conductivity is also studied over a temperature range of 450–100 K. On the basis of the temperature dependence of dc conductivity, the conduction mechanism in this film of a-Se 70Te 30 nanorods is elucidated. The results show that the thermally activated process is responsible for the transport of carriers for the temperature range of 450–300 K. For temperature region 300–100 K, the conduction takes place via variable range hopping (VRH). Therefore, three dimensions Mott's variable range hopping (3D VRH) is applied to explain the conduction mechanism for the transport of charge carriers for temperature region 300–100 K. In optical properties, optical absorption measurements of the thin film of a-Se 70Te 30 nanorods are also carried out in the wavelength range 400–900 nm. These studies indicate that the absorption mechanism is due to indirect transition. The optical band gap is estimated to be 1.18 eV.