Laser Spectroscopy of the Ar(1s3,5) and CH in Ar + CH4 DBD for a-C:H Deposition System

Abstract

A dielectric barrier discharge in Ar and CH4 gas mixtures used for a-C:H film deposition was investigated. The number densities of Ar(1s2: resonant level) and Ar(1s3,5: metastable levels) atoms were measured using a high sensitive detection method based on plasma modulation and laser absorption spectroscopy. The CH(X2Π) radical number density was measured by an actinometry method. The excitation transfer process from the Ar(1s5) atom to the CH(A2Δ) radical was detected by a laser collisionally induced fluorescence method. The a-C:H film properties (the content of sp3 and sp2 hybridization and the content of the CH3 and CH2 hydrocarbon groups) were correlated with the number densities of the Ar(1s5) atom and the CH(X2Π) radical. In the a-C:H film, maximum value of the sp3/sp2 was obtained, when the CH(X2Π) number density in DBD plasma was minimum.