Compositional and structural analysis of hydrogenated amorphous silicon-nitrogen alloys prepared by plasma-enhanced chemical vapour deposition

Amorphous hydrogenated silicon-nitrogen alloys (a-Si1-xNx:H), having energy gaps in the range 2.0-5.2 eV, have been deposited in ultra-high vacuum by 13.56 MHz plasma-enhanced chemical vapour deposition from SiH4+NH3 gas mixtures with NH3 percentages in the range 6.2-97.3%. The compositions of the films were obtained by Rutherford back-scattering spectroscopy and elastic recoil detection analysis and the structure and the bonding configurations studied by infrared and Raman spectroscopies. Films having a nitrogen content x in the range 0.07-0.63 and a hydrogen content as high as 38 at.% have been obtained. For x < 0.5, the hydrogen is mainly bonded to silicon and nitrogen is prevalently incorporated in the NSi3 configuration. For x > 0.5, NHn bonds become predominant, which allows the growth of stoichiometric and overstoichiometric films.