Abstract: An apparatus for depositing synthetic diamond on a surface of a substrate includes a deposition chamber and a cooling block having a surface in the deposition chamber that is cooled by heat exchange. The substrate is supported from the cooling block so that the bottom surface of the substrate is spaced from the cooling block surface by a gap, and a gas is provided in the deposition chamber and in the gap, the gas comprising at least 30 percent hydrogen gas. A plasma deposition system forms in the chamber a plasma containing hydrogen gas and a hydrocarbon gas for depositing synthetic diamond on the top surface of the substrate.

Abstract: A method for depositing a substance, such as diamond, by plasma deposition on a substrate mounted over a madrel cooled by a heat exchange, comprising the steps of: determining the heat flux at the deposition surface of the substrate; providing, between said mandrel and said substrate, a spacer having a thermal conductance in its thickness direction that varies in accordance with said determined heat flux; and depositing said substance on said substrate by said plasma deposition.

Abstract: An apparatus for depositing a substance with temperature control includes, in one embodiment: a mandrel rotatable on an axis; a spacer mounted on the mandrel; a substance mounted on the spacer; a plasma, containing constituents of the substance being deposited, directed toward the substrate; the spacer having a thermal conductance in its thickness direction that varies with radial dimension.