Obstinate electrons 'ignore' assumptions and follow another path

Obstinate electrons 'ignore' assumptions and follow another path
Atomic force microscopy image (17 nanometres by 15 nanometres) showing rows of nanowires on a germanium surface.

(Phys.org)—It is possible to make gold wires so thin that there is not even enough room for electrons to pass one another. It's as if they were driving down a one-lane motorway, this has a major impact on traffic flow. But exactly what path do the electrons take? Measurements made by researchers at the University of Twente's MESA+ Institute for Nanotechnology supplied the answer. Surprisingly, it was found that the electrons do not move through the nanowires themselves, but through the "troughs" between them. The researchers demonstrated this in a recent article published in the prestigious journal Nature Physics.

The nanowires, which have a cross-sectional area of no more than one square nanometre (a nanometre is one millionth of a millimetre), are attached to a substrate made of the semiconductor germanium. The virtually defect-free nanowires are spaced at intervals of just 1.6 nanometres. This forces electrons to adopt one-dimensional behaviour.

Parallel or perpendicular

In a recent paper in , German researchers stated that electrons show this behaviour in a direction parallel to the gold nanowires. Their research showed that the "motorway lanes" are located along the gold nanowire "ridges". Japanese researchers responded by stating that the electrons actually move in a direction that is perpendicular to the alignment of the gold nanowires.

Researchers from the Physics of Interfaces and Nanomaterials group, which is headed by Prof. Harold Zandvliet, decided to test these ideas, by creating a spatial image of the electrons' conduction path. So who was right? The Germans were right, to the extent that the electrons do move parallel to the nanowires. However, charge transport takes place in the "troughs" between the nanowires, not along the themselves. As a result, the study sheds surprising new light on the behaviour of at the .

Explore further

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More information: "Origin of the Au/Ge (001) metallic state" by R. Heimbuch, M. Kuzmin and H.J.W. Zandvliet was published as "correspondence" in Nature Physics 8
Journal information: Nature Physics

Citation: Obstinate electrons 'ignore' assumptions and follow another path (2012, October 24) retrieved 22 August 2019 from https://phys.org/news/2012-10-obstinate-electrons-assumptions-path.html
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Oct 24, 2012
Doesn't this make sense though? Why would you expect electrons to move along the wires, smacking into atoms, when they can move freely in the spaces between them?

@Tausch - Not sure exactly what you're asking, could you perhaps clarify your question?

Oct 24, 2012
This makes so much sense, it could explain the incredibly low resistance of graphene.

Oct 24, 2012
it would be fun to shine a laser in the throughs to make sort of a quantum transistor or for racetrack memory

Oct 24, 2012
The diameter of a gold atom is about 0.15 nm, the wire itself is just 1.6 nm. Electron flow is conducted along the outer orbital electron shell. So 1.6/.15=10.66 means the diameter of the wire itself is just 10.66 atoms. Just cranking up the emf beyond an optimal threshold could cause such increased electron density causing loosely bound outer orbital electrons to be forced beyond the outermost electron shell. In such a case some electrons are forced to travel in a corridor between atoms because they can never reach the outermost electron shell for conduction.

Oct 24, 2012
I wonder what the "troughs" are made of.

Oct 25, 2012
Troughs should just be a void channel defined by outer electron shell coincidence of the gold nanowire atoms and the germanium substrate beneath. I'd think if there was something else in the trough it would have an impact on the behavior of the conduction transport. Guess this opens up more questions as to whether the AFM probing to create, image and charge the nanowaire structure was done in a hard vacuum or a atmospheric volume. If the work was done at a vacuum the troughs would nearly be true voids but in atmosphere you would have a gas channel that could ionize and change the entire behavior of the system. As AFM probing and micromachining is usually done in low atmospheric or vacuum state conditions I would expect the experiments were done under a very low torr or milli torr atmospheric state. That's the problem with these science news blurbs or tidbits at Phys.org - they usually have enough information to be misleading or deceptive about a finding but not enough for validity.

Oct 25, 2012
As to the why of the electrons preferring to surf the void between the wires rather than in,on or through the atomic structure of the nanowire will probably be due to the charge field characteristics of the system of both the substrate media and the conductor material. This device is sort of a nano valve or directional conductor array and since germanium is a semiconductor material the perceived behavior of current flow may be more like a fixed state switch/valve than just a simple conduction transport behavior. Interesting reading enough to make getting the actual article from Nature Physics a serious consideration. Another thing is that even though nanomaterials science is an established field we - even with familiarity of its ground rules tend to keep thinking about physical properties or behaviors as macro events or occurrences.

Oct 25, 2012
People have this all wrong. The electrons barely move what propagates is dipoles. Since there are few studies of dipole movement physicists will continue to encounter these unexplained phenomena explained with highly technical [read incorrect] conjectures.

Oct 25, 2012
What is the charge field strength inside a long conductor with circular cross section.


All conduction in principle - but not practice - occurs a the surface of a conductor.

In this case, the wires are so small that the thickness of the surface effect has a depth that is the same order of magnitude as the gap spacing between the wires.

Oct 25, 2012

"I wonder what the "troughs" are made of." - The Know

Smaller troughs.

Oct 25, 2012
its not that different from vacume tubes and diodes or is it?

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