With a transmission electron microscope, researchers are able to carve out complex metal devices that could be useful in applications as diverse as quantum electronics and nanofluidics
Researchers interested in how electrons travel through nanoscale systems, such as DNA or a thin strip of metal, are always faced with the challenge of making electrical contact to such tiny objects. Moreover, some measurements may require unique device geometries that are difficult to engineer with standard techniques.
Now, Michael Fischbein and Marija Drndic1 at the University of Pennsylvania in the United States have developed a flexible technique for making nanometric metal devices in a wide variety of shapes. They start by evaporating a thin metal film onto a suspended membrane of insulating silicon nitride. Electron-beam lithography is used to prepattern an area in the metal a few tens of nanometres in size, before the assembly is turned upside down in the path of a high-energy electron beam. The electron beam 'knocks off' the thin metal without damaging the silicon nitride, and is driven by hand to carve out fine features, such as nanoholes or nanogaps, in the metal.
The nanometre-sized devices remain part of larger metal electrodes, which can be easily contacted. Moreover, arbitrary shapes, such as serpentine wires and channels, can be fashioned in a variety of metals. Fischbein and Drndic find very low electrical noise in their devices, suggesting they will have the sensitivity necessary for measurements in quantum electronics and nanofluidics.
Fischbein, M. D. & Drindic, M. Sub-10 nm device fabrication in a transmission electron microscope. Nano Lett. 10.1021/nl0703626 (2007).
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Thomas, J. Body sculpting. Nature Nanotech (2007). https://doi.org/10.1038/nnano.2007.155