Fabrication and actuation of customized nanotweezers with a 25 nm gap

By combining conventional silicon microfabrication and direct three-dimensional growth using electron-beam induced carbon contamination, we have developed a scheme for fabricating nanotweezers with a gap of 25 nm. Four silicon oxide cantilevers with a spacing of 1.5 mum extending over an edge of a silicon support chip, were covered with a thin layer of metal. By focusing an electron beam at the ends of the cantilevers, narrow supertips grew from the substrate. Careful alignment of the substrate made the supertips converge to form a nanoscale gap. We demonstrate customization of the shape and size of the tweezer arms, using a simple scheme that allows conveniently fine-tuning of the tip features and the gap to within 5 nm. The supertips can be metallized subsequently, to be made conducting, without significantly affecting the shape of the tweezers. By applying a voltage on the outer electrodes with respect to the inner two electrodes, the gap can be opened and closed. This enables the device to grab and manipulate small particles, with the option of direct electrical measurement on the particle. The advantage of our approach is that no voltage difference is applied between the tweezer arms, making the device ideal for application with such fragile structures as organic objects.