Investigation on the Intermixing of Cu and In Layers for the Formation of Cu2In2O5 Thin Films

Abstract

For the first time, this research focuses on the inexpensive technique of synthesis of Cu2In2O5 thin films using intermixing of Cu and In layers, deposited using radio frequency (RF) magnetron sputtering technique. Further, structural, morphological, and optical characterization of Cu2In2O5 thin films have been carried out. The layered films were sputtered using Cu and In targets. The layered structure was subjected to post-deposition annealing at temperatures varying from 700 °C to 1000 °C in a constant oxygen ambiance for five hours. Decomposition of the single-phase Cu2In2O5 takes place at 1000 °C, resulting in the appearance of CuO, In2O3, and Cu2O as decomposition products. Descriptive analysis of the formation of the aforementioned products have been included. However, single-phase Cu2In2O5 thin films were obtained at a post-annealing temperature of 900 °C. The oxidation states of In and Cu have been studied through XPS analysis. Full width half maximum (FWHM), peak positions, satellite peak positions, and their respective binding energies have been elucidated through XPS analysis. An increase in the grain size from 36.8 nm to 115.8 nm with an increase in the annealing temperature from 700 °C to 1000 °C, was noticed from the FESEM images. Optical studies were performed on all the annealed films in the 200–2000 nm wavelength range. The bandgap was in the range of 2.88 to 3.46 eV for the films annealed between 700 °C to 900 °C. The refractive index of the single-phase Cu2In2O5 thin film was obtained to be 1.51.