The effect of nitriding on the diamond film characteristics on chromium substrates

In this report, we present a study of diamond deposition on pure and nitrided chromium substrates using the hot filament-assisted chemical vapour deposition technique. Deposition was performed at substrate temperatures varying from 475 to 750 degreesC for different exposure times. Scanning electron microscopy (SEM), micro-Raman spectroscopy and X-ray diffraction (XRD) techniques were employed to study the modified interlayers and diamond films. The high solubility and diffusivity of carbon in pure chromium result in an increased incubation time for diamond nucleation. However, even a 4-5-mum-thick nitrided layer is efficient as a diamond-nucleating surface, with a reduced incubation time as compared to pure chromium. Fully covering and adhering diamond films were obtained on the nitrided Cr specimens at temperatures between 550 and 750 degreesC. As a result of the nitriding process, the nitride diffusion layer reduces the carbon solubility at the substrate surface, thereby reducing the incubation time for diamond nucleation. Due to the strong chemical and mechanical bonding of the diamond films to the nitrided Cr substrates, the residual compressive stresses are accommodated, leading to adherent, continuous diamond films. The present study, however, also indicates an optimal low-temperature deposition condition to obtain a continuous diamond film directly on pure Cr. (C) 2002 Elsevier Science B.V. All rights reserved.