The control of the surface roughness and morphology of diamond films is of critical importance for many applications such as for optical and electronic components. In order to produce uniform CVD diamond films with a controlled surface morphology over large areas, bias enhanced methods of nucleation offer better reproducibility than substrate pre-treatment methods such as mechanical abrasion. Hot filament chemical vapour deposition (HFCVD) with bias enhanced nucleation (BEN) has been used to increase thr nucleation density of diamond films on Si{100} substrates. Optimal conditions of the nucleation step for subsequent growth of good quality diamond were a substrate temperature of 1100 K; methane/hydrogen ratio of 3%; pressure of 20 Torr; filament temperature of similar to 2500 K; d.c. bias of - 250 V and time of 30 min. We also demonstrate that re-nucleation of diamond is possible using short intervals of substrate biasing during normal diamond growth. The film morphology and surface roughness critically depend on the length of the bias cycle and may be controlled without reducing the diamond quality. The morphology and quality of the standard negatively biased and pulsed biased films were characterised by scanning electron microscopy and Raman spectroscopy. Atomic force microscopy was used to measure the surface roughness of the films.