Synthesis of ultra thin α-alumina nanobelts from aluminum powder by chemical vapor deposition

Ultra thin α-alumina nanobelts with single-crystalline rhombohedral structure were obtained by oxidizing Al in moisturized air under reduced pressure. It was found that the length and width of the nanobelts increased with sintering time. By preparing the samples in different environments, it was demonstrated that the presence of oxygen was essential to the formation of the alumina nanobelts, while the presence of water vapor substantially increased the yield. The epitaxial growth of the nanobelts was also studied. Belts tended to grow parallel to the (0 0 0 1) sapphire substrate, but 60° and 90° to the ( 1   0   1 ¯   0 ) and the ( 1   1   2 ¯   0 ) substrates, respectively. The vapor–solid mechanism and molecule impinging model were proposed to describe the growing process. This method provides a simple and cost-effective route for preparing α-alumina nanobelts.