Microstructure of SiC deposited from methyltrichlorosilane

Micro- and nanostructure of silicon carbide deposited at a pressure of 90 kPa and temperatures of 900, 1000 and 1100 °C from a methyltrichlorosilane/hydrogen mixture of 1:4 were investigated by TEM, HRTEM and energy-filtering diffraction (EFD); the chlorine content was studied by PEELS. The deposit at 1100 °C is characterized by highly textured, heavily faulted columnar β-SiC with some α-SiC, which should result from a twinning transformation. At the lower temperatures of 1000 and 900 °C Si is co-deposited. Simultaneously, smaller sized and less perfect nanocrystals of β-SiC are formed. At 1000 °C the nanocrystals of β-SiC and Si are separated by a weakly crystallized interphase; at 900 °C the nanocrystals are randomly dispersed in a disordered matrix phase. Chlorine is detected in all samples. Fringe patterns of some areas of the matrix phase at 900 °C show an interplanar distance of 0.44±0.02 nm which corresponds to that of polychlorosilane, [SiCl2]n. This correspondence suggests condensation of polychloro- and probably also of polycarbochlorosilanes during the deposition process at low temperatures.