Effect of annealing temperature on structure and electrical properties of topological insulator Bi₂Te₃

Bi₂Te₃ samples were prepared by precipitation method. The samples were annealed in evacuated quartz tubes and were treated at different temperature for different duration of time. Effects of annealing temperature and time on the structure of Bi₂Te₃ were studied in detail. The Bi₂Te₃ samples annealed at temperature 300°C and 450°C for 48Hrs, 72Hrs and 96Hrs were selected for the present study. The structure of Bi₂Te₃ and related phases were investigated by the X-ray powder diffraction technique. Morphology and chemical compositions of the samples were investigated by scanning electron microscope and energy dispersive X-ray spectroscopy respectively. All the samples were indexed in rhombohedral crystal structure, with a space group R-3m. The structure consists of repeated quintuple layers of atoms, Te2-Bi-Te1-Bi-Te2 stacking along the z-axis of the unit cell. Electrical properties of the sample annealed at 300°C for 96Hrs was evaluated by measurements of the electrical resistivity and magnetoresistance. The magnetoresistance data at low temperature (1.5 to 50 K) were analyzed to investigate weak antilocalization (WAL) effect. MR data followed the Hikami–Larkin–Nagaoka (HLN) equation with a fit parameter α close to −1 as expected for topological surface states at 1.5 K, but for other temperatures the small oscillations were observed which may be due to the phenomena like Shubnikov-de Hass effect.