Improved Synthesis and Electrical Properties of Si-Doped α-Fe2O3 Nanowires

We report an improved method to synthesize alpha-Fe2O3 (hematite) nanowires (NWs) via thermal oxidation that significantly reduces reaction time while improving NW density and uniformity. Stress introduced by shot-peening the starting steel foils and the relief of such stress seem to play an important role in promoting uniform one-dimensional growth. Water vapor is also shown to strongly influence both the density and the morphology of the grown nanostructures. Furthermore, although the as-grown NWs exhibit the high average resistivity (4 x 10(2) +/- 4 x 10(2) Q.m) associated with undoped hematite, chemical vapor deposition of silane coating these NWs, followed by an annealing step, produces silicon-doped alpha-Fe2O3 NWs that exhibit a significantly improved average resistivity of 4 x 10(-3) +/- 6 x 10(-3) Q.m. High-resolution electron microscopy, elemental mapping by EDS, and further study of their electrical properties attribute the increased conductivity to lattice doping. These doped hematite NW arrays are promising candidates for potential application as photoanodes in photoelectrochemical solar cells.