Annealing effects on the microstructure and photoluminescence properties of Ni-doped ZnO films

Ni-doped ZnO (ZnO:Ni) films were fabricated on Si(0 0 1) substrates by reactive electron beam evaporation at low substrate temperature. The as-grown films were then annealed in oxygen ambient at higher temperatures. X-ray diffraction (XRD) results indicated that 5 at.% Ni-doped samples are still of single phase with the ZnO-like wurtzite structure. Photoluminescence (PL) measurements of Ni-doped samples illustrated the UV-PL emission centered at about 384 nm, which is ascribed to the nearband- edge (NBE) emissions of ZnO-like band structures. The UV-PL intensity becomes stronger along with the increase of annealing temperatures and reaches a maximum magnitude after annealed at 450 8C. However, along with the further increase of annealing temperatures, UV-PL intensity diminishes again. The UV-PL intensity of 450 8C-annealed samples is 213 times stronger than that of as-grown (doped) samples, which may render potential applications in optoelectronic devices, such as UV luminescent devices. # 2003 Elsevier B.V. All rights reserved.