Cluster model of DC-glow discharge enhanced diamond nucleation

A theoretical model of DC-glow discharge promoted diamond nucleation is sug gested based on a semiempirical quantum chemical study of carbon clusters c onsisting of a few atoms. Under the standard thermodynamic conditions, the formation of planar aromatic is polyaromatic structures is energetically fa vorable. The influence of the DC-glow discharge is modeled through a shift in the substrate surface potential which, in turn, determines a shift in th e valence state ionization potential (VSIP) of atoms adsorbed on the surfac e. When changes in VSIP exceed 4 eV, the pi-interaction of 2p-orbitals of c arbon is suppressed. This effect causes the stabilization of tetrahedral, t wined and icosahedral structures over the aromatic ones for small carbon cl usters. This effect becomes more pronounced as the cluster size increases. These structures are consider to be precursor for diamond growth under chem ical vapor deposition (CVD) conditions. (C) 1999 Elsevier Science B.V. All rights reserved.