Tip-induced oxidative nano-machining of conducting diamond-like carbon (DLC)

Abstract

Electrically conducting diamond-like carbon films have been nano-machined by local deposition of thermal energy at the tip-to-film point of contact; the process is implemented on an atomic force microscope platform. Features with linewidth resolution down to 20 nm have been demonstrated; lateral irregularities along edges were less than 5 nm, while the radius of curvature at the edges was less than 10 nm; and the slope of features was limited by the aspect ratio of the tip. The mechanism arises from prompt thermal oxidation by intermittent transfer of heat from an ohmically heated tip, where Fowler–Nordheim tunnelling is likely to play a role in completing an electrical circuit when the physical continuity of the thermal circuit is interrupted. When heat transfer is insufficient to ensure prompt oxidation, then formation of a metastable low-density carbon phase is found to take place. That phase will then, at room temperature and in the presence of oxygen, relax back to a ‘normal’ higher density phase over a period of one hour. The many desirable physico-chemical properties of diamond-like carbon, in combination with the good spatial resolution of local probe methodology, suggest that the outcomes could have significant implications for next-generation nano-machine and nano-templating technologies.