We performed a parametric study on the synthesis of crystalline silicon nanoparticles in a capacitively-coupled plasma. Nanoparticle crystallinity was measured by Raman spectroscopy and nanoparticle size was measured by transmission electron microscopy. A floating-type probe was employed to measure the electron temperature and ion flux of the plasma. Results show that the crystallinity is improved under high ion flux and low gas pressure plasma conditions. It was also found that addition of hydrogen leads to decreased nanoparticle crystallinity by lowering ion impact energy. (C) 2010 Elsevier B.V. All rights reserved.