Formation of grain boundary structure under growth of silicon films with fibrous structure

We conduct a statistical analysis of the grain boundary structure of undoped polycrystalline silicon films. We study the effect of thickness on the formation of grain boundary structure in undoped polycrystalline silicon films using transmission electron microscopy and atomic force microscopy. The fibrous structure observed in films obtained by low-pressure chemical vapor deposition indicates the leading role of twinning processes in the formation of this type of structure in silicon films. We analyze the mechanism of twin complex growth and find that various types of triple and multiple grain boundary junctions are observed in silicon films with a fibrous structure; the ratio of these junctions is determined by the film thickness. The formation of the different junction types is associated with the mechanisms of film growth. Our analysis of the experimental data shows that the formation of multiple grain boundary junctions in the films is due to processes such as multiple twinning, splitting of grain boundaries, and random meeting of several twin boundaries of the Σ3n type. The obtained results are important for the investigation of defect behavior and the development and fabrication of nano-scale systems using undoped polycrystalline silicon films.