Synthesis of Al-Catalyzed Si Nanowires Using the Al Remaining After Removal of Anodic Aluminum Oxide

Single-crystal, Al-catalyzed silicon nanowires were grown under atmospheric pressure using the dimpled feature of the Al metal that remained after removal of an anodic aluminum oxide (AAO) template directly formed on a Si substrate. Upon annealing in a hydrogen-rich atmosphere, the dimpled morphology of Al was transformed into a smooth, rounded shape in which Si nanodots were periodically embedded due to Si migration from the substrate. The positions of the nanodots were exactly the same as the positions of sawtooth features on the dimpled surface. Although Al-catalyzed silicon nanowires have been known to grow only under vacuum due to the tendency of Al to oxidize, these silicon nanodots, surrounded by residual Al, showed excellent resistance to oxidation under atmospheric pressure. These nanodots were also capable of acting as catalysts for the growth of nanowires, and played a role in determining the diameter of the nanowires. A thinner residual Al layer made it easier to form Si nanodots while reducing the size of the nanodots, which subsequently led to the growth of nanowires with smaller diameters and better crystalline morphology.