Structural changes induced by nitrogen in the a-Ge : H network

The structural modifications induced by the incorporation of nitrogen (2 at .%<C-N<6 at. %, C-N = N concentration) in radio frequency-sputtered hydroge nated amorphous germanium (a-Ge:H) has been studied by infrared spectroscop y. At all N concentrations there is a substantial increase of the density o f voids, as indicated by the strength of the absorption band associated wit h the surface-like stretching vibration of the Ge-H dipole. As C-N increase s, the peak position of this mode shifts to smaller values. These effects a re also detected through the analysis of the wagging vibration modes of the Ge-H dipole. Comparison of the present results with similar data for H-fre e a:GeN indicates that the presence of H in the reaction hinders the incorp oration of the NGe3 skeletal group, characteristic of beta-Ge3N4. The overa ll data indicate that almost all N incorporates in N-H and N-H-2 configurat ions, which are responsible for the formation of a large quantity of small- size voids. (C) 1999 American Institute of Physics. [S0021-8979(99)01106-8] .