A novel method was proposed for measuring the epitaxial growth rate of diamond by microwave plasma-assisted chemical vapor deposition (MPCVD). Cubo-octahedral crystals were formed on an Si(100) wafer and were used as the substrate in the homoepitaxial growth. Growth rates of the {100} and {111} were simultaneously measured from the change in the top view size of crystals. Thus, the relative growth rate of {100} to {111} was obtained without any limitation of its value. The homoepitaxial growth rate was strongly affected by the type of diamond faces, CH4 concentration in the gas phase, and deposition temperature. The growth rate of {100} was more dependent on CH4 concentration than that of {111}, while the activation energy for the [100] growth was about half that for the [111] growth. These tendencies were in accord with growth mechanisms proposed for each diamond plane. Reaction conditions were optimized based on the relative growth rate of (100) to (111) planes, and a highly oriented (100) diamond film with a quite smooth surface was formed on an Si(100) wafer.

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