The fundamental aspects of the growth of microcrystalline silicon are discussed in terms of the gas-phase reactions, as well as surface reactions of Si-related radicals and atomic hydrogen. The nucleation of crystallites is related to the Si-H complex, accompanied by the compressive stress caused by breaking the Si-Si bond due to atomic hydrogen. The nucleation is followed by epitaxial-like growth. The low-temperature epitaxy was studied on Si(001) surfaces between 100 and 500 degreesC. The dependence on the hydrogen dilution and deposition temperature of the epitaxial thickness reveals crystal growth facilitated on a homogeneous hydrogen-covered surface. Finally, requirements for high crystallinity and low defect density under high deposition-rate conditions are discussed. Powder formation and its suppression using the hollow-mesh method are also described. (C) 2003 Elsevier Science B.V. All rights reserved.