Investigation of diamond coatings on titanium substrates for electrochemical applications

Abstract Diamond coated titanium electrodes show outstanding properties in alkaline electrolytes as they are corrosion resistant by forming stable TiO 2 layers. This quality is of decisive importance for this kind of application. Boron doped diamond layers were deposited on Ti sheets by the hot-filament method, using Triethylboron (B(C 2 H 5 ) 3 ) as a boron source to produce electrodes for electrochemical applications. Ratios of (B(C 2 H 5 ) 3 ):CH 4 were varied between 0 and 10 000 ppm and silicon was used as a reference material. Diamond growth on metallic titanium is proceeded by the formation of an intermediate TiC layer, which ensures a good electrical connection between the Ti substrate and the diamond but leads to poor adhesion of the layers. Additionally, boron influences the interlayer formation due to the formation of borides or carbo-borides. Correlations between diamond layer adhesion and boron addition during diamond deposition can be shown. To examine the electrochemical properties of diamond layers with various morphologies, cyclic voltammetry measurements were carried out in different solutions (0.1 N H 2 SO 4 , 6 N NaOH). Thereby large potential windows up to 4.7 V could be observed. It could be shown that boron has a positive influence on diamond deposition on Ti substrates in terms of better adhesion corresponding with a very large potential window in acid as well as basic solutions.