Effect of Substrate Temperature on Cu₂-xO Growth for Enhanced Photodetector Performance in Visible Region

The present study investigates the effect of substrate temperature (30 °C–300 °C) on the sputter-deposited Cu2-xO films for improved photodetector performance in the visible region. Cubic structured Cu2O phase is observed for all deposited films through structural analysis. Increasing substrate temperature causes the formation of nanospheres with higher grain size at 200 °C confirmed by the morphological images. Moreover, all the deposited thin films show a strong absorption band in the visible region (526–550 nm). Among deposited films, a lower bandgap (2.02 eV) is observed for the film deposited at 200 °C due to the higher surface area-to-volume ratio and increased grain size. The better crystalline nature, more copper vacancy, and formation of nanospheres with a larger grain size of the film deposited at 200 °C result in higher mobility and conductivity. Furthermore, the photodetector performance of the Au/Cu2-xO/Au test devices is studied under the visible light ( <tex-math notation="LaTeX">λ </tex-math> = 530 nm) irradiation. Among samples, the sample grown at 200 °C showed higher photocurrent ( <tex-math notation="LaTeX">36.10~μ A </tex-math> ), <tex-math notation="LaTeX">Iₒₙ/Ioff </tex-math> ratio (183.50), photoresponsivity (1.127 A/W), specific detectivity ( <tex-math notation="LaTeX">22.40 × 10^11 </tex-math> Jones), and faster response times ( <tex-math notation="LaTeX">τ ᵣ </tex-math> = 92 ms and <tex-math notation="LaTeX">τ f </tex-math> = 84 ms) even at lower incident optical power density (0.1283 mW/cm2). These improved experimental results signify the potential of the fabricated test device at 200 °C for the optoelectronics devices.