Structural and optical properties of Be-doped ZnO nanocrystalline films by pulsed laser deposition

The heteroepitaxial BexZn1 − xO(x = 0.4) (BZO) thin films were deposited on sapphire (c-Al2O3) substrates by pulsed laser deposition (PLD). BZO targets were synthesized using a traditional solid-reaction method. BZO films were deposited at a various substrate temperatures with a fixed P(O2) = 26 Pa, and the thickness of the films are estimated to be about 200 nm. Based on the x-ray diffraction analysis, BZO thin films deposited at Tsub. = 550–700 °C exhibit c-axis preferred growth. BZO films deposited at 600 and 650 °C exhibit sharp absorption edges around 400 nm measured at room temperature. The optical energy gap obtained from the transmittance spectra is about 3.43–3.64 eV, which demonstrates a possibility of the band gap engineering with a BeO–ZnO alloy using a PLD method with a single BZO target. It has been found that the crystallinity as well as the band gap of BZO films is strongly influenced by the deposition temperature.