The structure and surface morphology of diamond films grown on (100) single crystal silicon substrates byHF-CVD technique usingH2:CH4 (100:1 sccm) gas mixture are reported. The diamond films were characterized by scanning electronmicroscopy, x-ray diffraction and Raman spectroscopy. The influence of substrate pretreatment on the surface morphology and structure of the deposited diamond films have been explored. SEM micrographs of the deposited diamond film without any substrate pretreatment were found to consist of scattered diamond nuclei of about 5 µm or less in diameter having cubo-octahedral shapes which clearly exhibit (100) and (111) planes of diamond latticewhich are not significantly clustered. As the pretreatment time increases to 20 minutes the diamond nuclei grow in number and clustering starts to dominate and the signals of secondary nucleation disappear. After 30 minutes pretreatment of the substrate the micrographs of the deposited films showed that the film was continuous and nicely faceted exhibiting predominant (111) surface morphology. Asuccessful attempt has been made to incorporate boron in easy and simple way in the deposited diamond films. It was found that the presence of boron introduced cauli-flower type features to diamond crystallites on micron scale.