Microcrystalline to nanocrystalline silicon phase transition in hydrogenated silicon–carbonalloy films

Abstract

Different classes of interesting materials (such as protocrystalline, microcrystalline andnanocrystalline) have been grown under conditions very near to those for themicrocrystalline phase. In spite of the importance of these materials, a clear pictureregarding their phase transitions is missing. A smooth transition from the microcrystallineto the nanocrystalline silicon phase, distinctly different from an abrupt order–disorderphase transition, has been demonstrated, for the first time, in hydrogenated silicon–carbonalloy films, prepared from a silane–methane gas mixture highly diluted in hydrogen, byvarying the rf power in a plasma enhanced chemical vapour deposition system. The studyhas also provided the signature of medium range order in hydrogenated silicon–carbon alloyfilms.