Pulsed laser deposited Ni_xMg_1−xO film characterization and band gap investigation

In this letter, transparent Ni_xMg_1−xO film with good surface quality were obtained by advancing pulsed laser deposition method. The surface morphology and optical properties were investigated by changing the substrate temperature and laser energy density. It was found that the surface quality of Ni_xMg_1−xO can be improved greatly through the rising of substrate temperature or increasing laser energy density. In this case, the optimal deposition parameter was at 500 °C–5 J cm⁻². The annealing process was proved having remarkable impact on the surface topography. The optical band gaps which range from 3.88 eV to 4.16 eV were obtained through UV–vis absorption spectrum, as the deposition temperature increasing, the blue shift of absorption edge happened. The annealing was found to broaden the band gaps of samples deposited at lower energy density but have no effect on the band gaps of samples deposited at higher energy density. The abnormal width of band gaps were found, we speculate that the element uniformity of film plays an important role in band gap engineering. (paper)