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).
The need for precise control and characterization of thin film deposition over a wide range of pressures and plasma conditions is of paramount importance. A novel probe designed to quantify nascent atomic species, particularly hydrogen, will be developed.
This probe will be used along with other techniques to enhance the deposition of diamondlike carbon (DLC) films. The main emphasis centers on the measurement of the atomic hydrogen fraction in the reactor discharge since this has been found to be fundamental importance, It is also proposed to measure the other basic plasma parameters such as electron density, electron temperature, the electron energy distribution function and the plasma potential.
It is proposed to develop a technique called Vaccum Ultraviolet (VUV) - Multiphon Laser Induced Fluorescence (LIF) to quantitatively measure atomic hydrogen concentration in the plasma during DLC deposition. Other plasma parameters will be simultaneously measured using the techniques of emission spectroscopy and Langmuir probe-the latter modified both for operation at high pressures (50-100 Torr) and with high frequency discharges (1-13.56 Mhz).
These measurements will be correlated with DLC film quality evaluated using surface characterisation techniques. Upon successful development of this probe a field application study on its industrial relevance will be undertaken.
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