In situ incorporation of silicon into a CVD diamond layer deposited under atmospheric conditions

Abstract

Chemical vapour deposited (CVD) diamond coatings were obtained by a laser-based plasma CVD process without a chamber at atmospheric pressure. The aim of this study is to influence the conductivity by incorporating silicon content into a diamond layer. The modification of the diamond coatings was carried out by the supply of a solid silicon carbide precursor into the plasma flame during the CVD process. In this way, the CVD process was combined with a physical vapour deposition process to incorporate in situ impurities into the diamond layer. The crystal structure of the diamond films was verified by Raman spectroscopy and secondary electron microscopy. To analyse the distribution of the incorporated silicon, focused ion beam profiles were produced and recorded by scanning electron microscopy. Hereby it is shown that the silicon is incorporated underneath, on top, and in between the polycrystalline diamond coating. Using backscattered electron microscopy, it was detected that the silicon content in the centre of the process position is lower than at the edges. No silicon signal could be detected inside the diamond crystals by wavelength-dispersive X-ray spectroscopy. The luminescence spectra showed a sharp peak at 738nm, which proves the existence of silicon-vacancy centres.A sheet resistance of 2.43MΩ±1.98MΩ was measured by a 4-point probe van der Pauw resistivity measurement on a single diamond crystal in the centre of the coating. Feasibility studies of electrical discharge machining of the diamond layers proved that the modification of conductivity was successful.