Variations of morphology and electrical property of diamond with doping using diborane in a methane-hydrogen gas mixture

The shape of isolated diamond particles and the surface morphology of diamo nd films were investigated at various boron concentrations. The diamond par ticles and films were deposited using a microwave plasma-assisted chemical vapor deposition method at 70 Torr with various diborane concentrations fro m 0 to 4000 ppm in hydrogen-2% methane gas. The shape of isolated particle changed from cubo-octahedron to octahedron via truncated-octahedron as the diborane concentration increased. The growth rate decreased rapidly and the n remained constant with further increasing diborane concentration. The cha nges of particle shape and growth rate were explained by the charge-polarit y model of cursor gas, and by the relative growth rate of (100) and (111) f acets, which were controlled by the boron concentration. The surface morpho logy of diamond films varied in accordance with the change of the shape of the diamond particles. The resistivity of the diamond film decreased owing to the increase of carrier concentration as the diborane concentration incr eased to 500 ppm, below which the shape of isolated diamond particles was c ube-octahedral. (C) 1999 Elsevier Science S.A. All rights reserved.