Tag Archives: Donald Eigler

A deep look at atomic switches

A July 19, 2019 news item on phys.org describes research that may result in a substantive change for information technology,

A team of researchers from Tokyo Institute of Technology has gained unprecedented insight into the inner workings of an atomic switch. By investigating the composition of the tiny metal ‘bridge’ that forms inside the switch, their findings may spur the design of atomic switches with improved performance.

A July 22, 2019 Tokyo Institute of Technology press release (also on EurekAlert but published July 19, 2019), which originated the news item, explains how this research could have such an important impact,

Atomic switches are hailed as the tiniest of electrochemical switches that could change the face of information technology. Due to their nanoscale dimensions and low power consumption, they hold promise for integration into next-generation circuits that could drive the development of artificial intelligence (AI) and Internet of Things (IoT) devices.

Although various designs have emerged, one intriguing question concerns the nature of the metallic filament, or bridge, that is key to the operation of the switch. The bridge forms inside a metal sulfide layer sandwiched between two electrodes [see figure below], and is controlled by applying a voltage that induces an electrochemical reaction. The formation and annihilation of this bridge determines whether the switch is on or off.

Now, a research group including Akira Aiba and Manabu Kiguchi and colleagues at Tokyo Institute of Technology’s Department of Chemistry has found a useful way to examine precisely what the bridge is composed of.

By cooling the atomic switch enough so as to be able to investigate the bridge using a low-temperature measurement technique called point contact spectroscopy (PCS) [2], their study revealed that the bridge is made up of metal atoms from both the electrode and the metal sulfide layer. This surprising finding controverts the prevailing notion that the bridge derives from the electrode only, Kiguchi explains.

The team compared atomic switches with different combinations of electrodes (Pt and Ag, or Pt and Cu) and metal sulfide layers (Cu2S and Ag2S). In both cases, they found that the bridge is mainly composed of Ag.

The reason behind the dominance of Ag in the bridge is likely due to “the higher mobility of Ag ions compared to Cu ions”, the researchers say in their paper published in ACS Applied Materials & Interfaces.

They conclude that “it would be better to use metals with low mobility” for designing atomic switches with higher stability.

Much remains to be explored in the advancement of atomic switch technologies, and the team is continuing to investigate which combination of elements would be the most effective in improving performance.

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Technical terms
[1] Atomic switch: The idea behind an atomic switch — one that can be controlled by the motion of a single atom — was introduced by Donald Eigler and colleagues at the IBM Almaden Research Center in 1991. Interest has since focused on how to realize and harness the potential of such extremely small switches for use in logic circuits and memory devices. Over the past two decades, researchers in Japan have taken a world-leading role in the development of atomic switch technologies.
[2] Point contact spectroscopy: A method of measuring the properties or excitations of single atoms at low temperature.

Caption: The ‘bridge’ that forms within the metal sulfide layer, connecting two metal electrodes, results in the atomic switch being turned on. Credit: Manabu Kiguchi

Here’s a link to and a citation for the paper,

Investigation of Ag and Cu Filament Formation Inside the Metal Sulfide Layer of an Atomic Switch Based on Point-Contact Spectroscopy by A. Aiba, R. Koizumi, T. Tsuruoka, K. Terabe, K. Tsukagoshi, S. Kaneko, S. Fujii, T. Nishino, M. Kiguchi. ACS Appl. Mater. Interfaces 2019 XXXXXXXXXX-XXX DOI: https://doi.org/10.1021/acsami.9b05523 Publication Date:July 5, 2019 Copyright © 2019 American Chemical Society

This paper is behind a paywall.

For anyone who might need a bit of a refresher for the chemical elements, Pt is platinum, Ag is silver, and Cu is copper. So, with regard to the metal sulfide layers Cu2S is copper sulfide and Ag2S is silver sulfide.

Nanoscience: the next 50 years?

Tomorrow, Jan. 15 2011, there’s going to be a Kavli Futures Symposium titled, Plenty of Room in the Middle: Nanoscience – The Next 50 Years. This a symposium is being hosted (as you may have guessed) by the Kavli Nanoscience Institute at the California Institute of Technology where (from the Jan. 12, 2011 news item on Nanowerk),

… an assembly of pioneering scientists will gather to focus on four key topics in nanoscience: atomic-scale assembly and imaging, mesoscopic quantum coherence, the “nano/bio nexus” and nanotechnology frontiers. Co-chairing the symposium are Michael Roukes, co-director of the Kavli Institute of Nanoscience at the California Institute of Technology, and IBM scientist Donald Eigler.

Unfortunately, they do not seem to be webcasting this event but there’s a transcript of a recent teleconference amongst three of the pioneering nanoscientists who will be gathering to discuss Feynman, his legacy, and the future. (The transcript is embedded in the news item on Nanowerk.)  The three scientists are:

  • IBM scientist Don Eigler
  • Angela Belcher Massachusetts Institute of Technology (MIT) materials scientist
  • David Awschalom University of California physicist

Here’s an excerpt from the transcript which gives you a preview of what they’ll be talking about tomorrow. This bit is where David Awschalom is discussing convergence in the sciences,

I believe that the broad umbrella of nanoscience is rapidly dissolving the traditional barriers between these disciplines, and maybe wiring them a bit together with the idea that now people are thinking about atoms and materials as arbitrary forms, not in the historical sense. Physicists are now using biological systems, and biologists are exploiting solid state devices and microfluidic devices within a myriad of research efforts. People are thinking much more broadly than in the past and, as Don [Eigler] says, I think it’s the discoveries in science that are driving this direction. When I look at the students who are entering the university system, they’re highly motivated by the idea of breaking down the normal barriers and focusing on the new scientific opportunities that emerge. I agree with Don. I think the idea of labeling things is wrong. This merging is going to happen very naturally. It’s already happening. For example, some researchers are thinking about photosynthesis as a quantum process, and [asking] whether photosynthesis is driven quantum mechanically in certain plants – exploring the concept of coherent energy transfer in biology. If so, it is possible to control this flow with exquisite precision. When you look in the literature, there are growing numbers of laboratories working in these cross-disciplinary areas; not because they’re suddenly interested in biology but they realize that biological systems could be tuned and engineered to explore unique scientific missions. So yes, I do believe that this merge is inevitable. I don’t think it’s going to be because of funding, or because of labeling, as Don says, but it’s where the interest is, and it where the new frontiers are in science.

I find this to be very interesting since it fits in very well with a recent presentation that MIT researchers made at a forum hosted by the American Association for the Advancement of Science (AAAS) earlier this month. From the Jan. 5, 2011 news item on Azonano,

A new model for scientific research known as “convergence” offers the potential for revolutionary advances in biomedicine and other areas of science, according to a white paper issued today by 12 leading MIT researchers.

The report, “The Third Revolution: The Convergence of the Life Sciences, Physical Sciences and Engineering,” noted the impact that convergence is already having in a broad array of fields.

Just as advances in information technology, materials, imaging, nanotechnology and related fields — coupled with advances in computing, modeling and simulation — have transformed the physical sciences, so are they are beginning to transform life science. The result is critical new biology-related fields, such as bioengineering, computational biology, synthetic biology and tissue engineering.

At the same time, biological models (understanding complex, self-arranged systems) are already transforming engineering and the physical sciences, making possible advances in biofuels, food supply, viral self assembly and much more.

What’s fascinating to me is that there doesn’t seem to any consideration of the societal implications of all this boundary crossing or convergence. Frankenfoods (genetically modified food) created a major panic because people were not comfortable with crossing certain types of boundaries. Once you take the ideas being proposed by the Kavli nanoscientists and the MIT researchers from theory to application, another dimension can open up.

Not all applications are hugely upsetting to society but some have the potential to cause havoc and they don’t necessarily have to cross boundaries. For example, computers created huge problems. I once had a technical writer tell me that she found bullet casings in some of the computerized equipment they received back from some small towns in northern British Columbia (Canada). People were afraid for their jobs. And, when I was working in the library system at the University of British Columbia, a librarian tried to sabotage the system; she didn’t use a gun or a rifle. Instead, when they were transferring information from card catalogues to online catalogues the librarian [started] taking large chunks of catalogue cards home with her, effectively hiding the information.

Stories like the one about the librarian might seem amusing now but there was genuine anguish and panic over the advent of the computer into daily life. Personally, I think the changes these nanoscientists are discussing are more profound and potentially disturbing.