Nanomorph Silicon Thin Films Prepared by Using an HW-MWECR CVDSystem

Abstract

We have prepared hydrogenated nano-amorph silicon (na-Si:H) films byusing a hot-wire-assisted microwave electron-cyclotron-resonance(HW-MWECR) chemical vapour deposition (CVD) system. The films aredeposited in two steps: in the first 9 min, a hydrogenated amorphoussilicon layer is deposited by using hydrogen-diluted silane with aconcentration of SiH4/(SiH4+H2) = 20%, andthen a nanocrystalline silicon (nc-Si) layer is deposited by usingvarious highly hydrogen-diluted silane. The Raman TO-like mode peak ofthe films was found in the range 497–508 cm−1. When the silaneconcentration used for preparation of the nc-Si layer is 14.3%, thefilm has a large crystalline volume fraction of 65.4%, a wide opticalband gap of 1.89 eV and a low hydrogen content of 9.5 at.%. Moreover,the na-Si:H films rather than nc-Si possess high photosensitivity ofabout 105.