Photoluminescence and infrared properties of α-Al2O3 nanowires and nanobelts

alpha-Al2O3 nanowires and nanobelts have been successfully synthesized from Al pieces and SiO2 nanoparticles at 1200 degreesC and 1150 degreesC, respectively, in a flowing Ar atmosphere. The alpha-Al2O3 nanowires are uniform with diameters of 20-70 nm and lengths of 15-25 mum, and the nanobelts are several to tens of micrometers long, with width of 0.1-1 mum and thickness of 10-50 nm. The growth of the nanowires is controlled by a vapor-liquid-solid (VLS) growth mechanism, while the growth of the nanobelts may be due to a vapor-solid (VS) process. Infrared spectra of these nanostructures are different from that of the bulk alpha-Al2O3. Photoluminescence (PL) measurements under excitation at about 255 nm show that the nanowires and nanobelts have emission peaks at 3 4 and 392 nm, respectively. On the basis of the discussion of the thermal annealing in different atmospheres such as O-2 and H-2 on the behaviors of the PL spectra, we suggest that optical transitions in oxygen-related defects, F+ (oxygen vacancy with one electron) centers, are responsible for the observed emission.