Nanocrystalline silicon is considered one of the most promising materials for thin-film solar cells. For such an application, one of the critical issues yet unsolved is to obtain a good structural uniformity along the film growth direction to yield high fill factors and open-circuit voltages. In this article, Raman spectroscopy was used to obtain crystallinity in-depth profiles of samples grown at a high growth rate by low-energy plasma-enhanced chemical vapor deposition (PECVD) using different SiH4 and H-2 fluxes, all yielding the same dilution factor. The results showed that the total flow rate strongly affects the structural uniformity of nanocrystalline silicon films. (c) 2008 The Electrochemical Society.