Mar 22, 2011
Nanopores reshaped into slits and stars
Solid-state nanopores are of great interest as developers hope to use the structures to characterize biopolymers, such as DNA, RNA and polypeptides. Within the highly confined space of a nanopore, down to a few nanometres, molecules can be detected by a variety of means. Now, besides tuning the size of the nanopore, researchers have deformed Si3N4 nanopores into many other geometries, including nanoslits and nanostars, using a high-energy convergent electron beam (CEB) in a high-resolution transmission electron microscope (TEM).
The team from Peking University, China, used a CEB in a high-resolution TEM (Tecnai F30, 300 kV) to reshape the structures. Circular nanopores were drilled in a few minutes when a high-energy electron beam was converged to a bright spot on free-standing Si3N4 membranes. By moving the CEB to an area near one corner of the nanopore, deformation with the desired geometry could be realized directly.
Painting with electrons
To achieve the anticipated pattern or structure, the irradiation spot of the electron beam can be moved at will, using it as a "paintbrush", starting from an initial nanopore and stopping when the desired geometry is obtained. Different geometries can be fabricated with the same nanopore sequentially.
Nanoslits with a 2 or 3 nm width and 100 nm length were realized by this approach (see image above), which can find applications as supporting membranes and masks. The geometry of nanostructures can be modified under irradiation of the electron beam to a lower surface free energy in the fluid state, with the help of the knock-on effect from the CEB.
The group's results provide a new perspective for nanopore-based device fabrication, which would open up more substantial opportunities for nanoelectronics and nanofuidics.
Additional details can be found in the journal Nanotechnology.
About the author
The study was conducted by researchers from the State Key Laboratory for Mesoscopic Physics, and Electron Microscopy Laboratory, at Peking University, China. Mr Song Liu is now a PhD candidate in physics at Peking University. He performed the nanopore fabrication and deformation experiment and was supervised by Dr Qing Zhao, now an associate professor at the School of Physics, Peking University. Dr Qing Zhao is currently working on nanopore-based device fabrication and its application for DNA detection. Prof. Dapeng Yu is leader of the nanostructure and low-dimentional physics group in the School of Physics at Peking University. The group's research covers a wide range of fields, such as transport properties and device applications of semiconducting nanowires, graphene and solid-state nanopores.