Laser-induced fluorescence measurements on the C2 Sigma +-X2IIr transition of the CH radical produced by a microwave excited process plasma

Abstract

Laser-induced fluorescence (LIF) measurements were made in a microwave (2.45 GHz) excited a-C:H deposition plasma using the uv beam of a frequency-double cw dye laser. Miscellaneous vibrational and rotational transitions of the electronically excited CH band system C2 Sigma +-X2IIr at lambda approximately= 314 nm were investigated. Spatially resolved rotational, vibrational and translational temperatures as well as drift velocities and densities of ground state CH molecules have been determined. The most important molecular constants for the transitions under investigation have been compiled and the evaluation procedure of UF signals is described. Deposition rates of a-C:H layers are measured by observing the temporal development of the interference fringe system on the substrate. The growth rate is compared with the CH flux to the target. A simplified model of the discharge plasma explains the measured data in a roughly quantitative manner.