GAS-PHASE SYNTHESIS OF NITROGEN-DOPED DIAMOND COATING USING A HIGH-VELOCITY MICROWAVE PLASMA FLOW

Nitrogen-doped polycrystalline diamond coating is synthesized by high-velocity gas jet chemical deposition from a methane/hydrogen mixture with an addition of molecular nitrogen. The reaction mixture is activated by microwave plasma. The present work reports a comparative study of morphology, composition, and structure of nitrogen-doped and undoped diamond coatings using scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and near edge X-ray absorption fine structure spectroscopy. It is shown that doping with nitrogen decreases the average size of diamond microcrystals and their quantity. Also, the addition of molecular nitrogen to the reaction mixture leads to the formation of higher quality diamond crystals comprising a smaller number of oxygen- and hydrogen-containing functional groups and graphite-like carbon. It is shown that the surface of the nitrogen-doped diamond coating contains ~0.6 at.% of nitrogen that exists in three chemical states and affects the hydrophilic properties of the coating.