Formation of cubic boron nitride films on nickel substrates

Cubic boron nitride (c-BN) films were synthesized by radiofrequency (r.f.) magnetron sputtering at a frequency of 13.56 MHz from an h-BN target. The s ubstrate used was high-purity polycrystalline nickel foil (0.125 mm thick). The deposition process was carried out in an Ar-N-2 gas mixture (in a rati o of 5:1) at a total pressure of 10-15 mTorr. The ion Bur impinging on the substrate was enhanced by an auxiliary electrode placed between the magnetr on and the substrate. The main deposition parameters included substrate tem perature and negative bias voltage. The films were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffract ion (XRD), Xray photoelectron spectroscopy (XPS) and scanning electron micr oscopy (SEM). By the proper cleaning procedure of substrate and parameter o ptimization, stable and adherent films with a c-BN fraction above 90% have been achieved. The substrate surface state and energetic bombardment, inclu ding the ion flux and energy, were essential factors controlling the format ion of sp(3)-bonded cubic phase during deposition. It was found that the ap plication of a negative bias voltage higher than 150 V at substrate tempera ture of 400-500 degrees C promotes the growth of c-BN phase. The present ex periment showed that nickel may also be a promising substrate material for the preparation of high quality and well adherent c-BN films under physical vapor deposition (PVD) conditions. (C) 2000 Published by Elsevier Science S.A. All rights reserved.