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

Abstract

The shape of isolated diamond particles and the surface morphology of diamond films were investigated at various boron concentrations. The diamond particles and films were deposited using a microwave plasma-assisted chemical vapor deposition method at 70 Torr with various diborane concentrations from 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 then remained constant with further increasing diborane concentration. The changes of particle shape and growth rate were explained by the charge-polarity model of cursor gas, and by the relative growth rate of (100) and (111) facets, which were controlled by the boron concentration. The surface morphology 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 increased to 500 ppm, below which the shape of isolated diamond particles was cubo-octahedral.