Optimization of Sputtering Power Parameters in Magnetron Co-Sputtering for High-Performance Flexible Pd-Doped Bi2Te3 Thermoelectric Films

Flexible n-type Pd-doped Bi₂Te₃ thin films were deposited on polyimide substrates using magnetron co-sputtering. The sputtering power of the Bi₂Te₃ target was varied between 30–50 W, while that of the Pd target was fixed at 4 W, yielding films with a thickness of ~500 nm. Vacuum annealing at 250 °C significantly improved the structural and thermoelectric properties. Surface morphology, crystal structure, composition, and transport characteristics were analyzed by FE-SEM, GI-XRD, EDS, and ZEM-3 measurements. Annealed films exhibited enhanced Bi₂Te₃ (015) orientation together with PdTe₂ (011) reflections, accompanied by higher Te content and reduced Pd incorporation. Seebeck coefficient analysis confirmed stable n-type conduction in all films. Importantly, increasing the Bi₂Te₃ sputtering power to 50 W lowered electrical resistivity and led to a maximum power factor of 8.0 × 10⁻⁵ W/m·K² at room temperature. These results demonstrate that optimizing sputtering conditions is crucial for achieving high-performance flexible Pd-doped Bi₂Te₃ thermoelectric thin films.