One-dimensional semiconductor nanostructures: Growth, characterization and device applications

One dimensional (1D) inorganic materials are gaining increasing attention because of their unique structural features and interesting functional properties. Given the structural stability, they show promising application potential in vacuum as well as in oxidizing atmospheres, which provides them a competitive edge over their carbon-based counterparts. A number of synthetic procedures have been developed and demonstrated for 1D nanostructures that have led to intriguing morphological variations (wires, tubes, belts, rods, etc.), however the control over radial and axial dimensions remains a continuing challenge. In addition, the choice of material is rather limited. We have developed a generic approach for the size-selective and site-specific growth of nanowires by combining vapor-liquid-solid (VLS) approach with molecule-based chemical vapor deposition. The synthesis of nanowires (NWs) is based on the decomposition of discrete molecular species, which allows growing nanowires at low temperatures with a precise control over their diameter and length. The precursor chemistry can be tuned to facilitate the stripping of organic ligands and to achieve complete decomposition that is critical for maintaining the gas phase super-saturation necessary for ID growth. High-yield synthesis of elemental (Ge) and compound semiconductors (SnO2, Fe3O4, V2O5, In2O3) was performed by the chemical vapor deposition of appropriate metal-organic precursors. Axial and radial dimensions of the NWs were varied by adjusting the precursor feedstock, deposition temperature, and catalyst size. Finally, the device potential of these building blocks as photo- and gas sensors was investigated by integrating individual nanowires in electrical circuits using focussed ion beam (FIB) assisted nano-lithography.