NUCLEATION AND INITIAL GROWTH OF DIAMOND BY BIASED HOT-FILAMENT CHEMICAL-VAPOR-DEPOSITION

The nucleation and initial growth of diamond on Si(100) in biased hot filament chemical vapour deposition have been investigated by atomic f orce microscopy, scanning electron microscopy, and Raman spectroscopy. For positive bias values of 75 V, the nucleation density was found to be 10(6) cm(-2) for non-scratched silicon. The maximum value of the n ucleation density was over 10(11) cm(-2) on mirror-polished Si(100) at -300 V. The transportation process of the ion flux from the filament to the substrate is discussed in detail for biased substrates. The nuc leation enhancement by the positive bias is believed to be a result of the increased impingement of the electrons emitted from the filament to the substrate surface. The studies have shown that electron emissio n from diamond plays a key role in negative-bias-enhanced nucleation b y accelerating the dissociation of molecular hydrogen and hydrocarbon species into various free radicals and causing a plasma to be ignited near the substrate surface. The negative bias pretreatment is also a c ritical step in growing heteroepitaxial diamond films: the enlargement of the area of diamond clusters in contact with the substrate enhance s the orientated growth of the films.