Influence of Oxygen Flow Rate on the Phase Structures and Properties for Copper Oxide Thin Films Deposited by RF Magnetron Sputtering

This study examines the impact of varying oxygen flow rates on the properties of Cu2O thin films deposited via radio frequency (RF) magnetron sputtering. X-ray diffraction (XRD) analysis showed a phase transition from cubic Cu2O to a mixed Cu2O and CuO phase, eventually forming a Cu4O3 tetragonal structure as oxygen content increased. The surface morphology and cross-sectional structure of Cu2O thin films observed through field emission scanning electron microscopy (FE-SEM) were found to vary significantly depending on the oxygen flow rate. X-ray photoelectron spectroscopy (XPS) indicated notable variations in the chemical states of copper and oxygen. The Cu 2p spectra revealed peaks around 933 eV and 953 eV for all samples, with the S01 sample (deposited with only argon gas) exhibiting the lowest intensity. The S02 sample showed the highest peak intensity, which then gradually decreased from S03 to S06. The O 1s spectra followed a trend with peak intensity being highest in S02 and decreasing with further oxygen flow rates, indicating the formation of complex oxides such as Cu4O3. UV-Vis-NIR spectroscopy results demonstrated a decrease in transmittance and optical band gap energy with increasing oxygen content, suggesting a decline in crystallinity and an increase in defects and impurities. These findings underscore the critical role of precise oxygen flow rate control in tailoring the structural, morphological, compositional, and optical properties of Cu2O thin films for specific electronic and optical applications.