Diamond growth on hard carbon films

Abstract

A three-step process for enhancing the nucleation density of diamond on unscratched silicon substrates using microwave-plasma-enhanced chemical vapor deposition is described. Hard diamond-like carbon (dlc) films with thickness in the range 5–100 nm were first formed on smooth (100) silicon surfaces using a vacuum-arc plasma deposition technique at room temperature. The dlc-coated silicon substrates were subsequently subjected to a low-temperature pretreatment with a methane-rich plasma for an hour before switching to the diamond nucleation conditions. To investigate the effect of the dlc film structure on diamond nucleation, experiments with silicon substrates coated with evaporated carbon films approximately 50–100 nm thick were also performed under similar pretreatment and diamond nucleation conditions. Diamond films with nucleation density about 2 × 10 8 cm −2 were obtained with pretreated dlc films, depending on the film thickness and the pretreatment time, whereas in the absence of the pretreatment and/or with evaporated carbon films the diamond nucleation density was less than 10 4 cm −2. The significant enhancement in diamond nucleation density obtained with pretreated dlc films is attributed to the inherently high etching resistance of the films resulting from the high fraction of sp 3 bonds. The actual nucleation sites might be very fine carbon or, possibly, SiC particles produced by etching back the dlc film.