engleski

Estimation of amorphous silicon thin films density by optical methods

Due to leak of long range ordering, density of amorphous silicon is lower than in its crystalline form. By hydrogenation of material, the density difference becomes larger. In order to study the effect qualitatively, the series of thin amorphous hydrogenated silicon films with large variation in hydrogen to silicon ratio, deposited by magnetron sputtering, was examined by UV-visible-IR spectroscopy and nuclear methods. The film density of deposited films was estimated by using tree different approaches. In the first one, the density was estimated by using EMA (Effective Medium Approximation) analysis of long wavelength dielectric function. In particularly, the basic and modified Bruggeman and Maxwell-Garnett models were tested. The second set of values for density was obtained by analysis of stretching vibrations of Si-H bonds in IR part of spectrum, by using earlier published method. These results were compared with the results obtained by nuclear methods, allowing the discussion of compatibility and accuracy of all of applied methods. The final result, density variation in a-Si:H samples deposited by magnetron sputtering as a function of hydrogen to silicon ratio, was compared with results of density measurements made on the samples deposited by other techniques. The qualitative and quantitative matching allows some concluding remarks upon intrinsic structural property of amorphous Si:H material.

amorphous hydrogenated silicon; density; efective medium approximation; ifra red spectroscopy

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