Systematic study of the growth of aligned arrays of α-Fe2O3 and Fe3O4 nanowires by a vapor-solid process

Growth of aligned and uniform alpha-Fe2O3 nanowire (NW) arrays has been achieved by a vapor-solid process. The experimental conditions, such as type of substrate, local growth and geometrical environment, gas-flow rate, and growth temperature, under which the high density alpha-Fe2O3 NW arrays can be grown by a vapor-solid route via the tip-growth mechanism have been systematically investigated. The density of the alpha-Fe2O3 NWs can be enhanced by increasing the concentration of Ni atoms inside the alloy substrate. The synthesized temperature can be as low as 400 degrees C. Fe3O4 NWs can be produced by converting alpha-Fe2O3 NWs in a reducing atmosphere at 450 degrees C. The transformation of phase and structure have been observed by in situ transmission electron microscopy. The magnetic and field-emission properties of the NWs indicate their potential applications in nanodevices.