Deposition of high-quality diamond films on technology important substrates such as semiconductor silicon is a difficult problem due to inherent interdiffusion problems between substrates and diamond overlayers. To overcome this difficulty the concept of the buffer layer has been utilized and good quality diamond films have been deposited on Si(100) substrates with different kinds of buffer layers. Aluminum nitride (AIN), titanium nitride (TiN), carbon nitride (CNx), and tungsten carbide (WC) as buffer layers have been studied for diamond nucleation enhancement. Scratching the silicon substrate surface with a diamond paste has also been investigated for diamond nucleation enhancement on Si (100) substrates. The deposited diamond films have been characterized with Raman spectroscopy, and scanning electronic microscopy (SEM) techniques. This study shows that the use of a buffer layer is very effective in enhancing the nucleation rate of diamond films. Finite-volume based computational fluid dynamics has been used to model flow, transport, gas-phase, and surface chemical reactions.