|
ZnO is gaining substantial interest day by day because of its wide bandgap (3.4 eV) and large exciton binding energy (60 meV) due to which lasing emission is possible from ZnO based materials even above room temperature. Here we are reporting the influence of growth temperature and annealing ambient on photoluminescence properties, crystalline size and surface morphology of ZnO thin films deposited on Si substrates at 200°C by RF sputtering. Achieved thickness is 198 nm as confirmed by Profilometer. Grown samples were further rapid thermal annealed at 800°C in Ar, N2, O2, and in vacuum ambient. The as-grown sample did not exhibit any near band edge emission peak due to presence of deep level defects. Low temperature (18 K) photoluminescence spectra exhibited strong emission peak around 3.32 eV when the as-grown sample was annealed at 800° C in oxygen ambient which indicates defects state passivation. A lowest full width half maximum (FWHM) of 73.85meV was achieved for sample annealed in O2 ambient .Sample annealed in vacuum showed peak with highest intensity at 3.25eV, which corresponds to donor-bound-acceptor (DAP). High resolution Xray diffraction measurement exhibited a dominant <002> peak. Atomic Force Microscopy also revealed surface roughness of 7.72 nm for sample annealed in O2 ambient.
|
