Effect of Precursor Gas on Growth Temperature and Electrical Conduction of Carbon Nanowalls in Microwave Plasma-Enhanced Chemical Vapor Deposition

Moderate-pressure microwave plasmas are used to prepare nitrogen-incorporated carbon nanowalls (CNWs) by chemical vapor deposition using acetylene and methane as precursor gases. The growth temperature range for acetylene is shown to be totally lower than that (>1000 °C) for methane, which is attributed to the difference in degree of hydrogenation of radical species in the two plasmas. The structural order and cluster size of sp2 carbon phase in CNWs characterized by the Raman spectroscopy increase initially and, then, decrease with temperature in each temperature range, showing the same trend as the inverse of the sheet resistance of CNWs. The results indicate that the carrier transport in CNWs depends exclusively on the microstructure of sp2 carbon phase, despite a large difference in the growth temperature range depending on the precursor gas.