Papers by Author: Kyo Hong Choi

Abstract: High purity nanowires are successfully synthesized by chemical vapor deposition. In this work, we have tried synthesis of GaP nanowires with copper oxide catalyst using chemical vapor deposition method involving a metal oxide-assisted vapor-liquid-solid (VLS) growth mechanism. The synthesis process is the same as that described in existing work except for a catalyst. The mixture of GaP and Ga powder was used as GaP source for synthesis of GaP nanowires. And the mixture powder was directly vaporized in the range of 700~1000°C under argon ambient in a furnace. The wire-like products was observed in the range of 800~950°C. The diameter of nanowires increases with increasing synthesis temperature, but reversely, the length of nanowires decreases steadily. The nanowires prepared at 850°C possess perfect wire-like shape and uniform distribution of diameter. The average diameter and length of nanowires are about 50
 and 150, respectively. HRTEM and EDX analysis were carried out to obtain more detailed information of its microstructure. Nevertheless, all condition of processing was set for making the high purity GaP nanowires as existing reported method, the nanowires were identified as well-crystallized gallium oxide nanowires with an amorphous outer layer. It does not accord with existing reported results. This result means that the catalysts play a key role in the growth of nanowires.

Abstract: Gallium phosphide nanowires were successfully synthesized by the catalytic chemical vapor deposition (CVD) method using MgO powder-impregnated nickel oxide as catalyst and gallium phosphide and gallium powders as GaP source. The synthesis of GaP nanowires were carried out at 900°C for 30min under argon ambient and directly vaporized Ga and GaP powder. The diameter of GaP nanowires is about 25~70nm and the length is up to several tens of micrometers. The GaP NWs was core-shell structure, which consists of the GaP core and the Ga oxide outer layers. The GaP nanowires have a single-crystalline zinc blend structured crystals with the [111] growth direction. Nanowires larger than around 50nm in diameter exhibited twinning faults, which appears in the TEM images as discrete dark lines and alternating wire contrast. We demonstrate that MgO powder-impregnated nickel oxide catalyst exhibited a large catalytic effect on the growth of high-purity and -quantity gallium phosphide(GaP).