Electron microscopic characterization of diamond films grown on Si by bias-controlled chemical vapor deposition
Diamond films grown by Bias-Controlled Hot Filament Chemical Vapor Deposition (BCCVD) on silicon (Si) substrates were characterized by Transmission Electron Microscopy (TEM). Both plan-view and cross-sectional TEM samples were made from diamond films grown under different biasing conditions. It was found that defect densities in the films were substantially reduced under zero and reverse bias (substate negative relative to the filament) as compared to forward bias. Furthermore, the diamond/Si interface of the reverse and zero bias films consisted of a single thin interfacial layer whereas multiple interfacial layers existed at the diamond/Si interface of films grown under forward (positive) bias. Tungsten (W) contamination was also found in the interfacial layers of forward bias films. It is concluded that forward biasing in the present condition is not favorable for growing high quality, low defect density, diamond films. The possible mechanisms which induced the microstructural differences under different biasing conditions are discussed.