Free-standing nanoscale gold pyramidal films with milled nanopores

Grant-Jacob, James, Brocklesby, William and Melvin, Tracy (2012) Free-standing nanoscale gold pyramidal films with milled nanopores. American Vacuum Society: 59th International AVS Symposium, Tampa, United States. 27 Oct - 02 Nov 2012.

Abstract

Thin films of micro and nanostructured metals are important for the construction of plasmonic devices and microelectromechanical systems (MEMs). The fabrication of individual metallic, pyramidal shells as well as ultra-smooth metal films with grooves, bumps, pyramids and holes has previously been demonstrated1,2, as has direct raster milling with 5 nm machining precision in 100nm thick gold films3. Routine fabrication of micro and nanostructured thin films is desirable. In this work, the fabrication of arrays of nanoscale pyramidal structures in free-standing gold films is demonstrated, and single nanopores are milled into the nanostructures for DNA translocation.

Silicon Klarite® pyramidal micro-structured substrates are an effective tool for surface enhanced Raman scattering (SERS) experiments, owing to the strong field enhancement within the pyramids. Here, the substrates are used as moulds for creating pyramidal structured gold as free-standing thin films. The silicon substrates contain an array of pyramids etched into a 4mm x 4mm square region on the substrate's surface. These pyramids are 1.5µm x 1.5µm square and 1µm deep on a pitch of 2m. An Edwards E306A Thermal Evaporator is used to coat silicon samples in a 50nm layer of Teflon® and then a 100nm layer of gold. Epoxy is then deposited on top of the gold layer using a pipette. Once the epoxy has cured, the epoxy together with the gold is mechanically lifted from the Teflon® coated substrate. The gold-coated epoxy is then placed over a micron-sized aperture and the epoxy dissolved away using acetone. Initial imaging is performed using a Carl Zeiss SMT, Inc., Evo® scanning electron microscope (SEM), while the subsequent imaging and milling of 50 nm holes through the free-standing gold is carried out using an Carl Zeiss SMT, Inc., Orion® Plus helium ion microscope (HIM). These films are suspended over micron-sized apertures for integration into platforms already proven for DNA translocation, and to optically interrogate the structures using Raman based techniques.

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Contributors

Author: James Grant-Jacob

Author: William Brocklesby

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