Photoluminescence and Infrared Properties of α-Al₂O₃ Nanowires and Nanobelts

Abstract

α-Al2O3 nanowires and nanobelts have been successfully synthesized from Al pieces and SiO2 nanoparticles at 1200 °C and 1150 °C, respectively, in a flowing Ar atmosphere. The α-Al2O3 nanowires are uniform with diameters of 20−70 nm and lengths of 15−25 μm, and the nanobelts are several to tens of micrometers long, with width of 0.1−1 μm 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 α-Al2O3. Photoluminescence (PL) measurements under excitation at about 255 nm show that the nanowires and nanobelts have emission peaks at 394 and 392 nm, respectively. On the basis of the discussion of the thermal annealing in different atmospheres such as O2 and H2 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.