X-ray photoelectron spectroscopy studies on the formation of chromium contacts to single-crystal CVD diamond

Au/Cr Ohmic contacts on p-type, heavily boron-doped, single-crystal CVD diamond have been studied using X-ray photoelectron spectroscopy (XPS) and electrical measurements. The interaction of chromium, a carbide-forming metal, with the diamond surface is discussed. The Cr/diamond contact formation process has been studied as a function of chromium thickness and post-metal deposition annealing. These data are correlated with specific contact resistances. The effect of annealing on the reaction between chromium and diamond has also been assessed by examining surfaces after removing the metal contact through wet etching. After removal of the metal the surface morphology of the diamond surface preparation was examined using AFM. Finally, new contacts have been fabricated on the reconditioned diamond surface and electrically characterised in order to assess the effect of surface roughness on the contact properties. These studies indicate that a significant interaction between carbon and Cr occurs during annealing of temperatures of greater than 400 °C.