Shape-controllable synthesis of indium oxide structures: Nanopyramids and nanorods

We describe a vapor-phase route to the controllable synthesis of indium oxide micro- and nanopyramids on the silicon wafer via selective epitaxial vapor-solid growth by a methane-assist thermal reduction method. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy revealed that the pyramids were cubic single crystals with a tetragonal symmetry. The size, morphology, and density of pyramids could easily be controlled by tuning reaction parameters. The method has good compatibility with other procedures involved in the microfabrication processes. Laterally grown indium oxide nanorods on the silicon wafer were also prepared via a vapor-liquid-solid mechanism. Those crystalline In₂O₃ nanorods were about 100 nm in diameter and 1 μm in length. The as-synthesized indium oxide nanopyramids and nanorods could offer novel opportunities for both fundamental research and technological applications.