Fabrication and actuation of customized nanotweezers with a 25 nm gap

Abstract

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 µm 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.

Comparative Study of Cu-Precursors for 3D Focused Electron Beam Induced Deposition

“…All precursors then show a decay of deposition rate with time ͑increasing tip length͒ inversely correlated to their initial growth rate, that is, most pronounced for ͑hfac͒Cu͑DMB͒, comparable for ͑hfac͒Cu͑VTMS͒ and ͑hfac͒Cu͑MHY͒, and smallest for Cu͑hfac) 2 . The deposition rate saturates at a certain minimum value depending on the precursor, although it is not reached for all precursors within the investigated time interval ͑0-20 min͒.…”

“…The minimum value of the AES measured Cu content should thus be closer to the original FEB decomposition whereas the maximum value should correspond to the postdecomposition/etching induced from the inspection itself. No measurable postdecomposition/etching takes place for the more stable precursors Cu͑hfac) 2 and ͑hfac͒CuMHY for which the Cu/C ratio of 1:5 to 1:6 is maintained throughout the measurement/sputter cycles. Hence decomposition of these precursors and reticulation of the remaining carbonaceous species seems to be complete which goes along with the estimated high electron/precursor flux ratios of 55-1500 for these precursors.…”

Controllable deformation of silicon nanowires with strain up to 24%

“…We expect this technique to have important biological applications such as capturing individual cells for further study. Compared to electrically actuated nanotweezers, 8 the polymer-controlled nanowires may be more densely packed, allowing the study of interactions between neighboring traps, and offer the ability to leave the tweezers closed without any external input.…”

“…However, even with current electron beam technology, alignment with accuracy greater than 10 nm is difficult. Mechanical manipulation using electrostatic actuation 8,9 requires power to be continuously supplied to the device to maintain deformation. Other static deformation methods-such as pseudomorphic growth-lack the ability to reversibly tune the amount of strain in the pillars once they have been patterned, and cannot achieve strain Ͼ2-3%.…”

Comparative Study of Cu Precursors for 3D Focused Electron Beam Induced Deposition

“…The ratios R 0,DMB :R 0,VTMS ϭ 47:20 ͑see Fig. 2A͒, and P DMB : P VTMS ϭ 30 ͑from 2 , the coverage is estimated to hfac ϭ 2.4% which should result in an initial deposition rate of about 1 nm/s, whereas 4 nm/s are observed experimentally. The parameter b of this Cu͑II͒ compound may be larger with respect to the ͑hfac͒Cu͑I͒-L family, due to stronger interactions of the surface with the more accessible out-of-plane Cu d orbitals, thus intuitively justifying the discrepancy.…”