Direct synthesis and strong cathodoluminescence of Al2O3 nanotubes

α-Al2O3 nanotubes were synthesized in bulk quantity by using simple physical evaporation of pure aluminum powders at 1000 °C. Field emission scanning electron microscopy and transmission electron microscopy observations show that the nanotubes have diameters smaller than 100 nm and lengths up to several microns. Cathodoluminescence measurements revealed a strong luminescence band in the wavelength range of 280-380 nm centered at 330 nm, which could be attributed to the oxygen vacancies in the α-Al2O3 nanotubes. Sacrificial template model is regarded as the possible formation mechanism of the nanotubes.