Effect of Heat Treatment on Structure and Electrical Properties of Bi₂Te₃ Magnetron Co-sputtered Films

The Bi₂Te₃ is one of the most promising thermoelectric materials for room temperature applications due to its narrow band gap and exceptional low temperature performance. In this study, Bi₂Te₃ films were fabricated using a multi-target magnetron co-sputtering process. The structural and electrical properties of these films were investigated under various annealing conditions, aiming to analyze the influence of annealing temperature on their characteristics. The results show that the annealing temperature significantly affects both the structure and electrical properties of Bi₂Te₃ films. Specifically, as the annealing temperature increases from 200 ℃ to 400 ℃, the grain growth becomes more pronounced perpendicular to the substrate while losing its directional consistency. At 400 ℃, a melt phase transformation occurs followed by recrystallization in the film. Concurrently, with the increase of the annealing temperature, the power factor of the film rises from 0.09×10^-3W·m^-1·K^-2to 0.21×10^-3W·m^-1·K^-2. When the annealing temperature increases to 400 ℃, the power factor of the film decreases to 0.16×10^-3W·m^-1·K^-2, reaching a maximum value of 0.21×10^-3W·m^-1·K^-2at the annealing temperature of 350 ℃.