Infrared and Raman Study of Amorphous Silicon Carbide Thin Films Deposited by Radiofrequency Cosputtering

摘要

Amorphous silicon carbide thin films have been deposited by radiofrequency cosputtering. These films were deposited from a composite target consisting of silicon fragments regularly distributed on the surface of a pure graphite disc for different relative silicon-to-carbon area ratio values (15%, 25%, 35%, 50%, and 65%), with a radiofrequency power of 250 watts. Structural properties of these films were investigated by Fourier transform infrared and Raman spectroscopy techniques. The infrared absorption spectra obtained on as-deposited films show the presence of two absorption bands, which are assigned to vibrational modes of silicon-carbon and silicon-oxygen bonds. The content of silicon-carbon bonds increases with increasing the relative silicon-to-carbon area ratio from 15% to 35% and then decreases for greater values. The maximum value of silicon-carbon bonds' content, occurring at about the relative silicon- to-carbon area ratio equal to 35%, indicates that this surface ratio value leads to the formation of nearly stoichiometric silicon carbide. The Raman spectroscopy measurements show that all the as-deposited films are amorphous and contain not only silicon-carbon bonds but also silicon- silicon and/or carbon-carbon bonds (sp~3and sp~2). The silicon-rich films contain mainly silicon bonds, while the carbon-rich ones contain mainly carbon bonds. The maximum content of silicon-carbon bonds for the relative silicon-to-carbon area ratio equal to 35% is confirmed by Raman results.