Synthesis of a BexZn1-xO Crystalline Film by Using RF Magnetron Co-Sputtering

A BexZn1-xO crystalline film was grown on an Al2O3 (0 0 0 1) substrate by simultaneous RF magnetron sputtering using ZnO and Be targets. The quality of the BexZn1-xO film and the variation of Be composition ratio at various substrate temperatures were studied using Xray diffraction, X-ray photoelectron spectroscopy (XPS), and transmission electronic microscopy. The BexZn1-xO film grown at 400 degrees C was observed to the best crystallinity and the highest Be composition ratio. The Be Is chemical bonding energy of Be-O at 113.2 eV was obtained from the XPS spectra and indicated that the sputtered elemental Be atoms occupy Zn sites in the ZnO matrix. The Be composition ratio varied from 13 % to 20 % with increasing substrate temperature from 200 to 800 degrees C, compared to that of the as-grown film. This indicates that the optical band gap energy of BexZn1-xO film can be tailed from 3.44 to 3.81 eV by controlling the substrate temperature.