Tag Archives: scanning tunnelling microscope (STM)

Off to the Nanocar Race: April 28, 2017

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The Nanocar Race (which at one point was the NanoCar Race) took place on April 28 -29, 2017 in Toulouse, France. Presumably the fall 2016 race did not take place (as I had reported in my May 26, 2016 posting). A March 23, 2017 news item on ScienceDaily gave the latest news about the race,

Nanocars will compete for the first time ever during an international molecule-car race on April 28-29, 2017 in Toulouse (south-western France). The vehicles, which consist of a few hundred atoms, will be powered by minute electrical pulses during the 36 hours of the race, in which they must navigate a racecourse made of gold atoms, and measuring a maximum of a 100 nanometers in length. They will square off beneath the four tips of a unique microscope located at the CNRS’s Centre d’élaboration de matériaux et d’études structurales (CEMES) in Toulouse. The race, which was organized by the CNRS, is first and foremost a scientific and technological challenge, and will be broadcast live on the YouTube Nanocar Race channel. Beyond the competition, the overarching objective is to advance research in the observation and control of molecule-machines.

More than just a competition, the Nanocar Race is an international scientific experiment that will be conducted in real time, with the aim of testing the performance of molecule-machines and the scientific instruments used to control them. The years ahead will probably see the use of such molecular machinery — activated individually or in synchronized fashion — in the manufacture of common machines: atom-by-atom construction of electronic circuits, atom-by-atom deconstruction of industrial waste, capture of energy…The Nanocar Race is therefore a unique opportunity for researchers to implement cutting-edge techniques for the simultaneous observation and independent maneuvering of such nano-machines.

The experiment began in 2013 as part of an overview of nano-machine research for a scientific journal, when the idea for a car race took shape in the minds of CNRS senior researcher Christian Joachim (now the director of the race) and Gwénaël Rapenne, a Professor of chemistry at Université Toulouse III — Paul Sabatier. …

An April 19, 2017 article by Davide Castelvecchi for Nature (magazine) provided more detail about the race (Note: Links have been removed),

The term nanocar is actually a misnomer, because the molecules involved in this race have no motors. (Future races may incorporate them, Joachim says.) And it is not clear whether the molecules will even roll along like wagons: a few designs might, but many lack axles and wheels. Drivers will use electrons from the tip of a scanning tunnelling microscope (STM) to help jolt their molecules along, typically by just 0.3 nano-metres each time — making 100 nanometres “a pretty long distance”, notes physicist Leonhard Grill of the University of Graz, Austria, who co-leads a US–Austrian team in the race.

Contestants are not allowed to directly push on their molecules with the STM tip. Some teams have designed their molecules so that the incoming electrons raise their energy states, causing vibrations or changes to molecular structures that jolt the racers along. Others expect electrostatic repulsion from the electrons to be the main driving force. Waka Nakanishi, an organic chemist at the National Institute for Materials Science in Tsukuba, Japan, has designed a nanocar with two sets of ‘flaps’ that are intended to flutter like butterfly wings when the molecule is energized by the STM tip (see ‘Molecular race’). Part of the reason for entering the race, she says, was to gain access to the Toulouse lab’s state-of-the-art STM to better understand the molecule’s behaviour.

Eric Masson, a chemist at Ohio University in Athens, hopes to find out whether the ‘wheels’ (pumpkin-shaped groups of atoms) of his team’s car will roll on the surface or simply slide. “We want to better understand the nature of the interaction between the molecule and the surface,” says Masson..

Adapted from www.nanocar-race.cnrs.fr

Simply watching the race progress is half the battle. After each attempted jolt, teams will take three minutes to scan their race track with the STM, and after each hour they will produce a short animation that will immediately be posted online. That way, says Joachim, everyone will be able to see the race streamed almost live.

Nanoscale races

…

The Toulouse laboratory has an unusual STM with four scanning tips — most have only one — that will allow four teams to race at the same time, each on a different section of the gold surface. Six teams will compete this week to qualify for one of the four spots; the final race will begin on 28 April at 11 a.m. local time. The competitors will face many obstacles during the contest. Individual molecules in the race will often be lost or get stuck, and the trickiest part may be to negotiate the two turns in the track, Joachim says. He thinks the racers may require multiple restarts to cover the distance.

For anyone who wants more information, go to the Nanocar Race website. There is also a highlights video,

Published on Apr 29, 2017

The best moments of the first-ever international race of molecule- cars.

Interfaces are the device—organic semiconductors and their edges

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Researchers at the University of British Columbia (UBC; Canada) have announced a startling revelation according to an Oct. 6, 2015 news item on ScienceDaily,

As the push for thinner and faster electronics continues, a new finding by University of British Columbia scientists could help inform the design of the next generation of cheaper, more efficient devices.

The work, published this week in Nature Communications, details how electronic properties at the edges of organic molecular systems differ from the rest of the material.

An Oct. 6, 2015 UBC news release on EurekAlert, which originated the news item, expands on the theme,

Organic [as in carbon-based] materials–plastics–are of great interest for use in solar panels, light emitting diodes and transistors. They’re low-cost, light, and take less energy to produce than silicon. Interfaces–where one type of material meets another–play a key role in the functionality of all these devices.

“We found that the polarization-induced energy level shifts from the edge of these materials to the interior are significant, and can’t be neglected when designing components,” says UBC PhD researcher Katherine Cochrane, lead author of the paper.

‘While we were expecting some differences, we were surprised by the size of the effect and that it occurred on the scale of a single molecule,” adds UBC researcher Sarah Burke, an expert on nanoscale electronic and optoelectronic materials and author on the paper.

The researchers looked at ‘nano-islands’ of clustered organic molecules. The molecules were deposited on a silver crystal coated with an ultra-thin layer of salt only two atoms deep. The salt is an insulator and prevents electrons in the organic molecules from interacting with those in the silver–the researchers wanted to isolate the interactions of the molecules.

Not only did the molecules at the edge of the nano-islands have very different properties than in the middle, the variation in properties depended on the position and orientation of other molecules nearby.

The researchers, part of UBC’s Quantum Matter Institute, used a simple, analytical model to explain the differences which can be extended to predict interface properties in much more complex systems, like those encountered in a real device.

“Herbert Kroemer said in his Nobel Lecture that ‘The interface is the device’ and it’s equally true for organic materials,” says Burke. [emphasis mine] “The differences we’ve seen at the edges of molecular clusters highlights one effect that we’ll need to consider as we design new materials for these devices, but likely they are many more surprises waiting to be discovered.”

Cochrane and colleagues plan to keep looking at what happens at interfaces in these materials and to work with materials chemists to guide the design rules for the structure and electronic properties of future devices.

Methods

The experiment was performed at UBC’s state-of-the-art Laboratory for Atomic Imaging Research, which features three specially designed ultra-quiet rooms that allow the instruments to sit in complete silence, totally still, to perform their delicate measurements. This allowed the researchers to take dense data sets with a tool called a scanning tunnelling microscope (STM) that showed them the energy levels in real-space on the scale of single atoms.

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

Pronounced polarization-induced energy level shifts at boundaries of organic semiconductor nanostructures by K. A. Cochrane, A. Schiffrin, T. S. Roussy, M. Capsoni, & S. A. Burke. Nature Communications 6, Article number: 8312 doi:10.1038/ncomms9312 Published 06 October 2015

This paper is open access. Yes, I borrowed from Nobel Laureate, Herbert Kroemer for the headline. As Woody Guthrie (legendary American folksinger) once said, more or less, “Only steal from the best.”