The nC-SiO(x):H films have been produced from He diluted SiH(4) plasma in RF glow discharge. Systematic oxygen incorporation in Si:H identifies a dehydrogenation process, demonstrating a reduced solubility of hydrogen in the SiO(x):H network. The dark-conductivity varies from 1.6 x 10(-2) S cm(-1) to 3.1 x 10(-6) S cm(-1) as the O-content (C(O)) changes from 0 to 15 at% and shows, in general, dual activation energies across similar to 310 K. The notable observation includes an irregular optical gap variation of the Si-network with the increasing oxygenation. A prominent narrowing of the optical gap has been demonstrated till the crystallinity in the material sustains, corresponding to an O-content of 2.2 at%. For C(O) > 2.2 at% the optical gap of the amorphous SiO(x):H network spontaneously widens. This opposite nature of optical gap variations and temperature dependent conduction mechanism exhibiting dual activation energy are explained in the frame work of three phase model of the network. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.034111jes] All rights reserved.