An MPCVD device capable of realizing effective doping comprises a reaction chamber and a gas input structure, wherein the gas input structure includes a first pipeline and a second pipeline for reaction gas, a first gas distributor connected with the first pipeline that uniformly transports gas as a first reactant into the reaction chamber through a gas outlet of the first pipeline located near the top of the reaction chamber, wherein the second pipeline uniformly inputs a doped reaction gas to a surface of a substrate through a second gas distributor in the form of a gas transport ring having a circular shape, wherein a height in the vertical direction of the gas transport ring connected with the second pipeline is substantially the same as that of a support for the substrate. The gas transport ring can be concentrically placed at a center position inside the support, or concentrically placed outside the support.

A method includes inserting a composite substrate into a reactor, where the composite substrate has a transverse coefficient of thermal expansion matching the transverse coefficient of thermal expansion of diamond throughout the range of 20 to 600 deg. C.; growing a layer of diamond upon a composite substrate via microwave plasma chemical vapor deposition. The composite substrate includes a deposition layer embedded within a base layer that is at least 6,000 times thicker than the deposition layer.

Elementary electrodes with at least two characteristic dimensions smaller than 1 m or 2.5 m, including a reactive surface, with characteristic dimensions smaller than 1 m or 2.5 m, a thin film of catalyst, part of the surface of which is comprised in the reactive surface, a thin film of carbon, in an allotropic form of carbon chosen from boron-doped diamond and nitrogen-doped amorphous non-hydrogenated carbon, in contact with the said thin film of catalyst and part of the surface of which is included in the reactive surface, a support, in contact with at least one of the thin films, enabling electrical measurements.

An electrolytic cell equipped with microelectrodes for the generation of un-separated products and the method for obtaining it. The cell and the microelectrodes are obtained using a technology for the production of microelectromechanical systems (MEMS). The anodic and cathodic microelectrodes have an electrocatalytic coating and are mutually intercalated at an interelectrodic gap lower than 300 micrometres.