THE NUCLEATION AND GROWTH OF LARGE-AREA, HIGHLY ORIENTED DIAMOND FILMS ON SILICON SUBSTRATES

Highly oriented diamond films can play an important role in replacing single crystal diamond for their use as substrates in active electroni c devices. However, for practical applications, large, homogenous film s with low defect densities are required. The focus of our investigati ons is the nucleation of highly oriented diamond on (001) silicon via Bias Enhanced Nucleation (BEN) over large areas. A modified BEN proces s using repetitive pulse bias 'RP-BEN' was developed, resulting in an area of oriented nucleation of up to 30 cm(2). The density of azimutha lly oriented diamond seeds was measured by scanning electron microscop y (SEM) images and found to be 8 x 10(8) cm(-2) with only 30% variatio n over the whole deposition area. After the nucleation, a microwave pl asma assisted chemical vapor deposition (MPACVD) resulted in highly or iented and [100] textured diamond films. X-ray diffraction (XRD) measu rements of the {111} diamond peak, for a 60-mu m-thick film, showed az imuthally misorientations (FWHM) of 2.8 degrees for the tilt and 5.5 d egrees for the rotation. Raman spectroscopy was used to evaluate the r adial distribution of the phase purity within the films. Introducing a final growth step with a low nitrogen concentration in the gas phase yielded a significant decrease in nitrogen incorporation in the films while maintaining the morphology. Elastic recoil detection (ERD) revea led impurity concentrations in the surface layer of 1.4 ppm for the N/ C ratio and 210 ppm for the H/C ratio. (C) 1998 Elsevier Science S.A.