TEM study of chemically converted SiC thin film on nanometer curved Si surface

Silicon whiskers with nanometer curvature have a variety of applications such as probes in STM and AFM, or field emission cathodes for vacuum microelectronic devices. For these and other applications it is essential to stabilize the sharply curved silicon surface during usage. Carburization of the silicon surface seems to be a very suitable solution to this problem, since SiC crystals have excellent physical properties and are chemically quite inert. There have been a number of reports of the carburization of flat surface silicon wafers by chemical reaction using both CVD and MBE methods. However, to carburize while maintaining a very sharp silicon tip is extremely difficult. It is also desirable to carburize only a very thin layer, so as to avoid excessive mechanical strain arising from the large difference (∼20%) in lattice parameters.Our carburizations were carried out in a turbo-pumped ultra-high vacuum system. The silicon specimens were oxidation sharpened and cleaned in a buffered HF solution.