Pattern-Free Growth of Carbon Nanotube Tips for Scanning Probe Microscopy

Carbon nanotube (CNT) tips on cantilevers have great potential of improving the resolution of scanning probe microscopy (SPM). In this study, we developed a process of growing CNT on silicon cantilevers by pattern-free chemical vapor deposition (CVD) method for the purpose of enabling CNT tip mass-production. Cobalt nanoparticle catalyst preparation and CVD conditions were optimized for growing sparse CNTs at the apex of each pyramidal tip of silicon probes. We have identified several key variables to ensure the high-yield of this process, such as the oxidation of silicon probes, amount of catalyst, annealing, ethanol temperature and CVD conditions. This process eliminates the need of patterning the wafer surface, simplified the catalyst preparation, and improved the CNT tip successful growth yield. The successful yield of the growth defined as the percentage of cantilevers with a single CNT protruding from the apex within an angle reproducibly reached or exceeded 60%, and showed promising potential for such process to scale up into mass-production.