Study of the electronic properties of Cu2O thin films by X-ray absorption spectroscopy

Abstract We have investigated the thickness effect of Cu 2 O thin films on the electronic structure deposited by the successive ionic layer adsorption and reaction (SILAR) method. Crystal, optical and electronic properties of the Cu 2 O thin films were studied by X-ray diffraction (XRD) and X-ray absorption near edge spectroscopy (XANES). According to the crystal structure analysis, films were determined to be mainly in cubic Cu 2 O structures. The XANES study have shown that Cu L 2,3 absorption edges are influenced by the chemical state of the Cu atoms strongly and a sole ionic picture is not enough to describe the L-edge spectra of Cu 2 O. It has been observed that Cu L 2,3 -edge spectra of the samples present typical electronic features of both monovalent Cu (I) and Cu (II) divalent states. The grains have an average size of 2.5 nm and XRD measurements revealed that ( 111 ) plane is the preferential orientation. Optical studies have shown that the optical absorption edge shifted to higher energies as the film thickness increases. It was found that the optical band gap was significantly influenced by the film thickness. Our results exhibited that the increment of the optical band gap of Cu 2 O thin films associated with a significant decrease of Cu-Cu interaction as a result of the increase in the film thickness.