Gradient layers of boron-doped diamond on titanium substrates

For the deposition of well-adhesive, low-doped diamond layers on titanium substrates a gradient layer is designed. At first a highly boron-doped diamond layer is deposited, which shows good adhesion to the titanium substrate, followed by a low-boron-doped diamond layer on the surface. The boron-doped diamond layers were deposited on titanium stretch metal substrates by the hot-filament CVD method. It is shown that with increasing boron content during diamond deposition above 6000 ppm B/C the intermediate Ti(C,B) layers becomes very thin and so at high-boron concentrations no problem with layer adhesion occurs. These Ti(C,B)-layers formed during diamond deposition were investigated by standard metallographic preparations. To form a diamond gradient layer on the highly boron-doped diamond the boron content was reduced and a low-doped diamond layer was deposited. Electrochemical cyclic voltammetric measurements show that the lower boron contents at the diamond surface provide better electrochemical properties. These layers show extraordinary electrochemical properties in respect of the gained hydrogen and oxygen overvoltage. (C) 2007 Elsevier B.V. All rights reserved.