Growth of Silicon Carbide Nanowires by a Microwave Heating-Assisted Physical Vapor Transport Process Using Group VIII Metal Catalysts

SiC nanowires are grown by a novel catalyst-assisted sublimation-sandwich method. This involves microwave heating-assisted physical vapor transport from a “source” 4H-SiC wafer to a closely positioned “substrate” 4H-SiC wafer. The “substrate wafer” is coated with a group VIII (Fe, Ni, Pd, Pt) metal catalyst film about 5 nm thick. The nanowire growth is performed in a nitrogen atmosphere, in the temperature range of 1650−1750 °C for 40 s durations. The nanowires grow by the vapor−liquid−solid (VLS) mechanism facilitated by metal catalyst islands that form on the substrate wafer surface at the growth temperatures used in this work. The nanowires are 10−30 μm long. Electron backscatter diffraction (EBSD) and selected area electron diffraction analyses confirm the nanowires to crystallize with a cubic 3C structure of 3C-SiC. EBSD from the nanowire caps are indexed as Fe 2 Si, Ni 3 Si, Pd 2 Si, and PtSi phases for the nanowires grown using Fe, Ni, Pd, and Pt as the metal catalysts, respectively. The nanowires are found to grow along the 〈112〉 directions, as opposed to the commonly observed 〈111〉 directions. The micro-Raman spectra from single nanowires indicate regions with varying compressive strain in the nanowires and also show modes not arising from the Brillouin zone center, which may indicate the presence of defects in the nanowire.