Temperature controlled phase transition and characterization of Cu2O and CuO thin films grown at different growth temperatures via mist CVD

This study investigates the phase-controlled copper oxide thin films by growth temperature using the mist-CVD methods. The main aim of the study is to determine the phase transition between Cu2O and CuO crystals in the range of 300 °C and 450 °C. It is found that 300 and 350 °C of growth temperatures showed only Cu2O cubic crystal phase, 400 and 450 °C of growth temperatures observed only CuO monoclinic crystals, confirmed by X-ray diffraction (XRD) and Raman spectroscopy measurements. A unique boundary in the crystal phase transition between Cu2O and CuO was shown. It was found to be an important parameter of the growth temperature to adjust the phase transition between CuO and Cu2O. The morphological examinations revealed by atomic force microscopy (AFM) and scanning electron microscopy (SEM), show that the surface roughness and grain shape are utilized to determine the phase transition. The optical properties from the UV-visible spectrophotometer show that the optical band gaps are reduced from 2.45 eV (Cu2O) to 1.38 (CuO) because of the phase transition. The low-temperature PL measurement is considered to provide insight into the defect structure and phase transition in Cu2O and CuO. The obtained results show that the growth temperature is a very effective way to control the phase transition between Cu2O and CuO crystals.