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Wear-Resistant Nanoscale Silicon Carbide Tips for Scanning Probe Applications



The search for hard materials to extend the working life of sharp tools is an age-old problem. In recent history, sharp tools must also often withstand high temperatures and harsh chemical environments. Nanotechnology extends this quest to tools such as scanning probe tips that must be sharp on the nanoscale, but still very physically robust. Unfortunately, this combination is inherently contradictory, as mechanically strong, chemically inert materials tend to be difficult to fabricate with nanoscale fidelity. Here a novel process is described, whereby the surfaces of pre-existing, nanoscale Si tips are exposed to carbon ions and then annealed, to form a strong silicon carbide (SiC) layer. The nanoscale sharpness is largely preserved and the tips exhibit a wear resistance that is orders of magnitude greater than that of conventional silicon tips and at least 100-fold higher than that of monolithic, SiO-doped diamond-like-carbon (DLC) tips. The wear is well-described by an atom-by-atom wear model, from which kinetic parameters are extracted that enable the prediction of the long-time scale reliability of the tips.