The substrate floating potential. Vs, was measured as a function of rf‐sputtering conditions using an electrostatic probe. The large negative Vs induced at low PAr is responsible for energetic ion‐bombardment at the growing film/plasma interface. This bombardment, when below a threshold potential ‐20V, results in local atomic rearrangement and selective resputtering, leading to minimization of microstructural defects. Results on film characteristics vs. Vs, H‐implantation in c‐Si, and Si‐H bonding vs. PH2 and Ts lead to a more complete picture of bombardment and thermal processes in a‐Si:H film formation.