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.