Luminescence and structural properties of ZnO thin films annealing in air

Abstract

All ZnO thin films deposited on (001) silicon substrates by DC reactive magnetron sputtering were annealed in air atmosphere with different times at 800°C. The samples were studied by X-ray diffraction technique (XRD), atomic force microscopy (AFM) and photoluminescence (PL) measurements. XRD investigation showed that ZnO phase was hexagonal wurtzite structure growing along the (002) direction. The as grown ZnO films presented macrostrain and microstrain caused a shift of the line diffraction (002) and a broadening respectively. However after 1 hour annealing these strains disappear. The grain size of ZnO films increased with an increase of annealing time. The as-deposited reactive sputtering ZnO films resulted semi-insulating with poor PL response. After high temperature annealing in air, the crystallinity and the PL response considerably improved, but their semi-insulating property also increased. The PL spectra of the annealed samples showed well defined transitions close to the near-band-edge and a wide visible deep-level band emission (430−640 nm). The main interest of this work was to enhance the PL response and to identify the origin of deep-level luminescence bands. The AFM, PL and XRD results indicated that the ZnO films annealing have potential applications in optoelectronic devices.