COMPARISON OF DIFFERENT METHODS TO CHARACTERIZE THIN A-SI-H FILMS

The objective of this work is to determine the materials properties of thin layers typically deposited for wall conditioning in fusion devic es. As reference material, a sequence of thin amorphous hydrogenated s ilicon layers with different thicknesses were produced on polished gla ssy carbon by Plasma Chemical Vapour Deposition PCVD, The films were c haracterised using AES, AFM, EPMA, ellipsometry, interference fringe a nalysis and RES. A second aim was to study the accuracy and reliabilit y of EPMA and RES measurements. The techniques applied provided values for refractive index, absorption coefficient, roughness, thickness an d elemental areal density. From the latter two, the density of the fil m could be determined. It turned out that the density derived by combi ning the results from different techniques was in good agreement. For the range of thickness investigated, the combination of ellipsometry a nd EPMA gave the most consistent values for the density with a maximum uncertainty of +/-5%.