The results, described in the Aug. 18, 2006, issue of Science,* are the first to be published about work at NIST's new Center for Nanoscale Science and Technology (www.nist.gov/public_affairs/releases/cnst.htm).
"It's still futuristic to talk about a real atomic switch but we're getting closer," says physicist Joseph Stroscio, lead author of the paper. In addition, by applying the findings to nanoscale fabrication on semiconductors and insulating thin films, it may be possible to develop new classes of electronic and magnetic devices constructed atom by atom.
In the work described in Science, NIST physicists used a custom-built, cryogenic scanning tunneling microscope (STM)--which provides a voltage and beam of electrons at its needle-like tip--to perform several different types of atomic scale measurements and manipulations. NIST theorists performed calculations of the atoms' electronic structure, which confirmed the experimental results.
A molecular chain of one cobalt atom and several copper atoms set upon a surface of copper atoms was constructed atom by atom using the STM in an atom manipulation mode. Then the STM was used to shoot electrons at the molecular chain and its effect on the switching motion of the cobalt atom was measured.
In addition, the team used a "tunneling noise spectroscopy" technique to determine how long the atom stays in one place. This measurement method was developed by two of the authors based on their 2004 discovery that an atom emits a characteristic scratching sound when an STM is used to move the atom between two types of bonding sites on a crystal** (see www.nist.gov/public_affairs/releases/hiphopatoms.htm).
"The two most important new findings," Stroscio says, "are an increased understanding of the science behind atomic switching and the development of a new measurement capability to spatially map the probability of an electron exciting the desired atom motion."
The scientists analyzed what happened to the atom switching rate as changes occurred in the STM voltage and in the current between the STM tip and surface. Above a threshold voltage of about 15-20 millivolts, the probability for switching per electron is constant, meaning that the electrons contain sufficient energy to move the cobalt atom. Higher currents result in faster switching.
The data suggested that a single electron boosts the molecule above a critical energy level, allowing a key bond to break so the cobalt atom can switch positions. The cobalt atom was less likely to switch as the molecular chain was extended in length from two to five copper atoms, demonstrating that the atom switching dynamics can be tuned through changes in the molecular architecture.
The researchers also found that the position of the STM tip is critical. They made this discovery by recording detailed noise measurements of the molecule with atomic scale resolution. An analysis of the noise enabled the team to make a spatial map of the switching speed and probability, showing that switching is most likely when the STM tip is positioned to the left of the cobalt atom. This finding is consistent with calculations of electronic structure and demonstrates the need to inject energy into a particular bond, according to the paper.
"This insight raises the possibility that molecular orbital analysis may be used to guide the design and control of single atom manipulation in nanostructures," the authors write.
Laura Ost | EurekAlert!
From rocks in Colorado, evidence of a 'chaotic solar system'
23.02.2017 | University of Wisconsin-Madison
Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
23.02.2017 | Physics and Astronomy
23.02.2017 | Earth Sciences
23.02.2017 | Life Sciences