MICROSTRUCTURAL PROPERTIES OF DC MAGNETRON SPUTTERED A-SIH BY IR SPECTROSCOPY

The amorphous hydrogenated silicon thin films, deposited by dc magnetron sputtering, were examined by near infrared and Fourier transformation infrared spectroscopy. It was found that, by increase of the hydrogen concentration from 6 to 32 at.%, the dielectric constant decreases and the frequency of absorption peak, corresponding to stretching vibrations of Si-H bonds, increases. The results were analyzed within the framework of effective medium approach assuming medium composed of Si network and voids decorated with hydrogen atoms. It is concluded that the increase of the hydrogen content is accompanied by an increase of void fraction in the total volume, with an increase of void 'decoration' with hydrogen and also with increased contribution of larger voids. The obtained dependence upon hydrogen concentration agrees well with density measurements and predictions made based on multiple-quantum nuclear magnetic resonance spectroscopy.