Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

Development of a novel hydrogen probe for plasma characterization and control during diamond film deposition

Measurements of the level of atomic hydrogen in a 13.56 MHz radio frequency plasma have been obtained during the deposition of diamond like carbon (DLC) films. 2 techniques were used, firstly a multiphoton laser induced fluorescence (MPLIF) system and secondly a novel combination of Langmuir probe and emission spectroscopy. In the latter technique the data obtained from electron energy distribution function (EEDF) measurements 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 obtained were compared with those obtained using the MPLIF technique which in turn can be calibrated using a hydrogen transfer standard which is calibrated by a titration technique. The hydrogen probe technique gave similar relative increases to MPLIF, but the atomic hydrogen concentrations were approximately a factor of 4 higher. More accurate electron collision cross sections and EEDF measurements should produce better agreement. The 2 techniques have been 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 film thickness, refractive indices and extinction coefficients. A correlation has been obtained relating the concentration of atomic hydrogen with the insitu ellipsometry data for films with refractive index between 1.6 and 2.1 (at 675 nm).

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Denis DOWLING