Surface chemical composition of SiC-cored nanowires investigated at room and elevated temperatures in ultra-high vacuum

Nanowires with SiC core were produced via Si/PTFE combustion synthesis in air and deposited from 1,2-dichloroethane suspension on an Au (111) surface. The dependence of the chemical bonding states on temperature (300-673 K) between different elements being a building material of nanowires' sidewalls was investigated by X-ray photoelectron spectroscopy (XPS) in ultra-high vacuum (UHV) conditions. Apart from silicon and carbon, the presence of oxygen and nitrogen was observed. Moreover, Si₃N₄ seems to be the second most important compound (after SiC) forming the amorphous outer shell of SiC nanowires. It is shown that carbon-containing compounds (oxides, nitrides, hydrocarbons) are substantially removed under annealing. It is also reported that a noticeable part of subsurface oxygen in the outer shell reacts with nitrogen at 473-573 K forming stable N-O bonds on nanowires' surface.