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Tuning the thermoelectric performance of flexible copper selenide thin films through sputtering pressure and hybrid microwave annealing
Author(s)
Khuncharoen, Wasan
Theekhasuk, Nattharika
Voraud, Athorn
Date Issued
October 10, 2025
Type
Article
Abstract
Flexible copper selenide (Cu₂₋ₓSe) thin films were deposited on polyimide substrates by direct current magnetron sputtering under varying pressures (0.8–4.0 × 10⁻² mbar) and subsequently annealed using hybrid microwave irradiation at 250 °C for 10–30 min. Increasing sputtering pressure raised the copper content (62.2–63.8 at%) and suppressed the formation of Cu₃Se₂ impurities. Hybrid microwave annealing promoted the transformation to stoichiometric β-Cu₂Se, removed oxide phases such as selenium dioxide and copper oxide, and improved crystallinity, as confirmed by x-ray diffraction and x-ray photoelectron spectroscopy. Field-emission scanning electron microscopy revealed microstructural densification at 10–20 min, whereas 30 min induced cracks and porosity that degraded transport properties. The optimized 20-minute annealed film achieved a peak power factor of 81.5 × 10⁻⁵ W/m·K² at 300 °C—over 130 times higher than that of the as-deposited film and comparable to other flexible Cu₂Se systems. Stability tests confirmed excellent retention after three months of ambient storage. These results establish sputtering pressure control and hybrid microwave annealing as scalable strategies for high-performance, stable Cu₂Se thermoelectric films.
Citation
Journal of Alloys and Compounds, 1041, 2025