A study of the role of the main plasma parameters on the transition from microcrystalline to amorphous silicon growth was performed, considering also the possibility to use plasma diagnostics for the prediction of this transition. Experimental measurements have shown that charged species do not play a significant role in the transition while Spatially Resolved Emission Spectroscopy was found to present a potential to be used as an in-situ diagnostic tool for the prediction of the transition. Calculations of the ion and hydrogen atom fluxes have shown that they both decrease in the transition region; however the hydrogen atoms flux was found to be about three orders of magnitude higher compared to the ion flux, implying a less important role of the later species in the transition. Possible scenarios concerning the energy transfer from hydrogen atoms and ions to the surface are presented and the limited case were ions can play a significant role on the deposition process is discussed. (c) 2005 Elsevier B.V. All rights reserved.