Defect structure of carbon rich a-SiC:H films and the influence of gas and heat treatments

A comprehensive study of carbon rich a-SiC:H films using optical absorption measurements, Fourier transform infrared spectroscopy, thermal desorption measurements, atomic force microscopy, and positron lifetime and Doppler-broadening techniques suggests that open volumes are formed in the films, due to incomplete breaking of the source molecule during film deposition. These open volumes are interconnected and can effectively trap gases from the ambient, during the film growth or after deposition. With increasing temperature the gases are desorbed from the internal surfaces of these open volumes and are released from the sample. This increases the areal density of the defects and is observable in positronium formation and annihilations of positrons with surface electrons. The growth of a nanocrystalline structure is observable upon annealing. At sufficiently high temperatures thermal breaking of Si-H and C-H bonds occurs and results in irreversible structural changes and film densification due to new C-C bond formation in the film. (C) 1998 American Institute of Physics. [S0021-8979(98)00114-5]