Apr 15, 2009
EBID shrinks nanopores to size
Nanopore fabrication usually involves a high-energy electron or ion beam to drill or sculpt nanopores in a thin membrane. Recently, it has been shown that the controlled deposition of material in a conventional scanning electron microscope (SEM) can be used to reshape existing nanopores and nanoslits as desired. What's more, this versatile technique has the potential to not only change the shape, but also the surface properties of existing nanopores.
Electron beam induced deposition (EBID) is a technique that converts molecules – called precursors – which are adsorbed on a surface, into solid material. The method has been used to create nanostructures on planar surfaces for several years already, but recently researchers at IMEC have shown that it can also change the shape, size, and probably also the surface properties of existing nanopores and nanoslits. Solid-state nanopores have received a lot of interest lately because of their potential application as single molecule detectors, but for them to work, accurate control over their size and surface properties is of great importance.
Firstly, nanopores with sizes of 50–150 nm were patterned in a membrane using electron beam lithography and anisotropic etching. The prepared nanopores were then loaded into a conventional Philips XL30 SEM inspection tool. When the electron beam was focused on the central part of the nanopore, the size of the hole was gradually reduced down to just a few nanometers, as shown in the figure above. Further characterization of the nanopores using techniques like EDX and EFTEM has revealed that the size reduction is caused by the deposition of carbon originating from the hydrocarbon contamination of the SEM, which serves as a precursor for EBID.
While this research has clearly shown the possibilities that EBID has to offer for nanopore fabrication, different precursors will have to be investigated to further control the surface properties of the resulting nanopores. This will allow researchers to tune the surface properties to match the application in mind.
This work was published in Nanotechnology.
About the author
Ronald Kox and Chang Chen are PhD students at KULeuven, carrying out their research at the IMEC research institute, in the functional nanosystems (FNS) group of Prof. Dr Liesbet Lagae. The FNS group covers a broad range of topics in nano-bioelectronics, like magnetic and plasmonic biosensors, nanoparticles and nanopores.