Nanoscale electronics achievable

Researchers at the University of Pennsylvania in the US have developed a simple, reliable and observable method of creating gaps between electrodes making the creation of nanoscale electronics more achievable.

These gaps are called nanogaps and make it possible to make electrical contact to structures on the nanoscale.

"A number of people have proposed nanoelectronic devices that use nanogaps, but nobody has been able to create nanogaps reliably in practice," said Marija Drndic, an assistant professor in Penn's Department of Physics and Astronomy in the School of Arts and Sciences. "For the first time, we were able to make the worlds smallest and cleanest nanometre gaps that can be imaged directly with atomic resolution. These nanogaps can be used to electrically connect small objects, such as an individual molecule."

This method hooks individual molecules to electronic circuits and is suitable for use in medicine, robotics, materials science and even security. Electronics on the nanoscale will also be used to create denser, faster storage devices and microprocessor chips.

To create these gaps, Drndic and graduate student Michael Fischbein used electron beam lithography, a common nanotechnology tool that uses electrons to create patterns on a surface. Their research succeeded because of the type of surface they used, thin layers of silicon nitride.

"Electron beam lithography works on small scale, but it is limited down to about 10 nanometres." Drndic said. "It is not like drawing a line on a page; as an electron beam hits a material the electrons tend to scatter forward and backward, which makes it difficult to create tiny lines."

While other research focused on breaking small wires to create nanogaps, similar to how a fuse can be popped open, the Penn researchers went the opposite route, making the gaps directly.

"Contrary to many expectations, the thin layer of silicon nitride, which we used instead of the usual xide on silicon, helped to minimise the amount of electron scattering to the point where we could make clean gaps," Fischbein said.

Just as important, these nanogaps are compatible with high-resolution transmission electron microscopy. Because nanogaps are created on thin films, it is easy to study the structure through high-resolution transmission electron microscopy and assess their quality.

Already the nanogaps have been used to measure electrical charge through several coupled nanocrystals, also referred to as quantum dots. Previous researchers have demonstrated that quantum dots can be manipulated to change their physical properties, particularly their optical properties.

"Nanogaps allow us to inject charge directly into individual nanocrystals, which may enable us to control their properties on a quantum level," Fischbein said. "It is a small gap, but across it we can bridge classical and quantum physics."

Item provided courtesy of University of Pennsylvania