Application of appropriate dc bias to the substrate has been identified as one of the efficient parameters, beyond the mostly used classical ones, in controlling the growth of nanocrystalline silicon (nC-Si:H) network by plasma CVD of Sift(4). The present communication demonstrates that applying negative dc substrate bias at the moderate level the overall nanocrystallinity in the material be enhanced significantly. The nC-Si:H film of similar to 70% crystalline volume fraction along with a high sigma(p)similar to 3.1 x 10(-4) S cm(-1) and E(sigma)similar to 191 meV has been obtained at a low substrate temperature of 200 degrees C and with a growth rate of similar to 8 nm/min from only 1 sccm of the feed gas SiH(4), using -75V dc substrate bias and He as the diluent to the plasma. Besides the extent of crystallinity, the average grain size (rho) has been demonstrated to be controllable within nano-dimensions, 1 < rho < 10 nm, by tuning negative dc substrate bias during plasma processing. The present report comprehensively elaborates the effect of applied negative dc substrate bias on the growth morphology of the nC-Si:H thin films from He-diluted SiH4 plasma, in view of controlling nanocrystallization at low substrate temperature by RF-PCVD, while controlled transmission of energy to the growing surface obtained from metastable and ionic helium (He* and He(+)) bombardment has been deemed instrumental. (C) 2011 Elsevier B.V. All rights reserved.