We apply a rate-equation pair binding model of nucleation kinetics to the nucleation of Si islands grown by hot wire chemical vapor deposition on SiO2 substrates. The grain size of poly-Si films increases with H-2 dilution, which is attributed to atomic H etching of Si monomers rather than stable Si clusters during the early stages of nucleation. The nucleation density increases sublinearly with time at low coverage, implying a fast nucleation rate until a critical density is reached, after which grain growth begins. The nucleation density decreases with increasing H-2 dilution (H-2:SiH4) due to etching, and with increasing temperature, due to enhanced Si monomer diffusivity on SiO2. From temperature-dependent measurements, we estimate the activation energy for surface diffusion of Si monomers on SiO2 to be 0.47 +/- 0.09 eV Simulations of the temperature-dependent supercritical cluster density lead to an estimated activation energy of 0.42 +/- 0.01 eV and an estimated surface diffusion coefficient prefactor of 0.1 +/-0.03 cm(2)/s. (C) 2003 Elsevier B.V. All rights reserved.