INFRARED-SPECTROSCOPIC INVESTIGATION OF SPUTTERED A-SI56GE44-N-H FILMS

The incorporation of nitrogen into a-Si56Ge44 prepared by dc magnetron sputtering has been investigated by means of infrared spectroscopy. Absorption bands appearing in the wavenumber region from 450 to 1050 cm-1 due to Si/Ge-N asymmetric stretching vibrations and Si/Ge-H wagging vibrations as well as Si/Ge-H stretching vibrations in the 1750-2300 cm-1 range were analyzed by a band separation procedure. The results indicate a preferential attachment of hydrogen to silicon and the dominance of the Si-N over the Ge-N bond for nitrogen concentrations below 10(22) cm-3. The addition of nitrogen to the sputtering atmosphere leads to a nitrogen content in the films proportional to nitrogen partial pressure. At partial pressures of some mPa, an increase of bonded hydrogen concentration where the relative effect on the Ge-H bond is stronger than on the Si-H bond is observed.