Films of μc-Si:H have been deposited in a conventional PECVD system in order to investigate their structural and morphological properties. They consist of a mixed phase of Si crystallites (50–200 Å), surrounded by grain boundaries, and amorphous regions. In this paper we report results obtained by different characterization techniques which have been used to deduce grain size, microcrystallinity fraction and composition of the crystalline, amoiphous and grain boundary. The amorphous matrix can be considered a covalent network where tetrahedrically coordinated carbon atoms, with 1 on 9 bonds terminated by hydrogen, exist. They form a distribution of large aromatic clusters containing a great number of aromatic rings such as to remarkably reduce the number of network terminators (hydrogen atoms).