Microstructure related characterization of a-Si:H thin films PECVD deposited under varied hydrogen dilution

Abstract

We report on the structure and optical properties of hydrogenated silicon thin films deposited by plasma - enhanced chemical vapor deposition (PECVD) from silane diluted with hydrogen in a wide dilution range. The samples deposited with dilutions below 30 were detected as amorphous hydrogenated silicon (a-Si:H) with crystalline grains of several nanometers in size which represent the medium-range order of a-Si:H. The optical characterization confirmed increasing ordering with the increasing dilution. The optical band gap was observed to be increasing function of the dilution.