At Georgia Institute of Technology in Atlanta, researchers investigating the use of molten gallium as a catalyst for the growth of silicon nanowires have fabricated novel silica nanowire structures. The groups of aligned nanowires resemble carrots (shown) and comets, and they include self-dividing wires that may have applications as nanometer-size optical splitters.The researchers, who reported their findings in the Feb. 27 issue of Journal of the American Chemical Society, attributed the growth of silica rather than silicon nanowires to oxygen leakage in the vacuum system. For the experiments, they employed the vapor-liquid-solid crystal growth technique, with the thermal decomposition of gallium-nitride powder serving as a source of the catalyst. Nanowires grown on a silicon substrate were 15 to 30 nm in diameter and displayed the carrot structure. Those grown on alumina were 50 to 100 nm in diameter and produced comets.