Quantitative measurements of atomic hydrogen during the deposition of diamond-like carbon films

Abstract

Abstract Measurements of the level of atomic hydrogen in a 13.56 MHz r.f. plasma were obtained during the deposition of diamond-like carbon (DLC) films. Two techniques were used, firstly multiphoton laser induced fluorescence (MPLIF), and secondly a novel combination of Langmuir probe and emission spectroscopy. In the latter technique the data obtained from electron energy distribution functions (EEDFs) and hydrogen emission line intensities were combined using a computer modelling technique to give the atomic hydrogen concentration. This system can potentially be used as a portable atomic hydrogen probe. The results were compared with those obtained using the MPLIF technique which was calibrated using a hydrogen transfer standard. The transfer standard was calibrated by titration. The two techniques were used to measure atomic hydrogen, initially in a hydrogen plasma and subsequently in acetylene-hydrogen containing plasmas during the deposition of DLC films. In conjunction with these measurements, in situ ellipsometry was used to obtain the film thickness, refractive indices and extinction coefficients. A correlation was obtained relating the concentration of atomic hydrogen with the in situ ellipsometry data for films with refractive index between 1.6 and 2.1 (at 675 nm).