Optical Emission Study of Radio-Frequency Excited Toluene Plasma

UV-visible emission spectra of radio-frequency (if) excited toluene plasma were studied. Benzyl radicals as well as toluene monomer and excimer were observed in toluene plasma. It was found that the intensities, peak positions, and linewidths of monomer and excimer emission bands exhibit strong dependence on rf power and plasma processing time. This can be ascribed to photochemical reactions in plasma. Gas-chromatographic analysis of the deposition products from toluene plasma indicated that the main component was bibenzyl. Spectroscopic evidence has shown that the bibenzyl molecule was formed by the coupling reaction between two benzyl radicals in plasma. The spectroscopic characteristics of toluene monomer and excimer are correlated with a kinetic model in plasma.