Diamond and cubic boron nitride: synthesis and electronic applications

This paper reviews recent progress in the deposition of diamond and cubic boron nitride (cBN) films. It aims at the effort of preparing smooth surfaces, improving crystallinity and enhancing adhesion of diamond and cBN films. The properties of these materials, multi-stage growth processes and difference in synthesis of diamond and cBN films are discussed. Resolving the nucleation and growth stages, deposition at different temperatures, post deposition treatment, possible chemistry, and the mechanisms behind are introduced as well. We report the most striking results achieved in our laboratories including the deposition of thin smooth oriented diamond film with coalescent diamond crystals and the deposition of thick cubic boron nitride films yielding well-resolved Raman spectra. The difference between the syntheses of polycrystalline and nano-crystalline diamond films are shown to be in gas phase environments. While the CH₃ radicals are responsible for the growth of polycrystalline films the CVD environment with abundant C₂ dimers results in the deposition of nanocrystalline diamond. Special attention deserves manufacturing single crystal diamond nanotips and their arrays. These single crystal diamond nano-lips have a very high aspect ratio, an apical angle of 28° and a radius of 5 nm. Finally, we present a review of potential and current applications of diamond in electronic areas.