The Effects of Selenization Treatment Temperature on the Phase Formation and Properties of Ba-Doped LaCuOSe Thin Films

In this study, barium-doped lanthanum copper oxide (LaCuO) thin films were deposited onto quartz glass substrates using a radio frequency (RF) magnetron sputtering system. The deposited films were subsequently subjected to a selenization annealing process to convert them into barium-doped lanthanum copper oxyselenide (LaCuOSe:Ba) thin films. Selenization was conducted at annealing temperatures of 750 °C, 800 °C, 850 °C, and 900 °C to determine the optimal processing conditions for achieving high-quality LaCuOSe:Ba films. Structural and compositional analyses were performed using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results indicated that the primary phase of the films under all conditions was LaCuOSe. However, at annealing temperatures above 850 °C, secondary phases, such as Cu2Se and La2O2Se, were formed, indicating partial decomposition or phase separation at elevated temperatures. Among the conditions tested, the film annealed at 850 °C exhibited the most favorable optoelectronic properties. It demonstrated an average visible light transmittance of 59%, an electrical resistivity of 6.37 × 10−3 Ω·cm, a carrier mobility of 5.87 cm2/V·s, and a carrier concentration of 2.15 × 1020 cm−3. These values yielded the highest calculated figure of merit for transparent conducting films, reaching 1.6 × 10−5 Ω−1, signifying an optimal balance between transparency and conductivity under these processing conditions.