A boundary between amorphous and microcrystalline growth of silicon thin films was explored for the study of grain growth by changing parameters of plasma enhanced deposition (Substrate temperature, silane dilution or deposition duration and thus the film thickness). Resulting series of a-Si:H/mu c-Si:H samples were characterized by values of dark conductivity and corresponding activation energy and prefactor, diffusion length, hydrogen content and morphology. The abrupt change of conductivity at the boundary is accompanied by a peak in surface roughness and diffusion length, which were connected to the formation of a percolating network of microcrystalline large grains. Results are discussed using the idea of barriers for electronic transport forming at the large grain boundaries. Comparison of transport properties with the hydrogen content pointed out the fundamental role of hydrogen present at the grain boundaries. (c) 2005 Elsevier B.V. All rights reserved.