Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists Image 'Magnetic Semiconductors' On The Nanoscale

31.07.2006
In a first-of-its-kind achievement, scientists at the University of Iowa, the University of Illinois at Urbana-Champaign and Princeton University have directly imaged the magnetic interactions between two magnetic atoms less than one nanometer apart (one billionth of a meter) and embedded in a semiconductor chip.

The findings, scheduled for publication as the cover story of the July 27 issue of the journal Nature, bring scientists one step closer toward realizing the goal of building a very advanced semiconductor computer chip. The chip would be based upon a property of the electron called "spin" and the related technology of "spintronics," according to Michael Flatté, professor in the UI College of Liberal Arts and Sciences Department of Physics and Astronomy.

"With spintronics, data manipulation and long-term storage can be conducted in one computer chip, rather than separately in a CPU and a hard drive as currently practiced. The data manipulation could also be done quicker and require less power. Such a computer would be much smaller in size and use less energy," Flatté says.

He adds that some 20 years ago, researchers at IBM discovered that an ordinary semiconducting material, indium arsenide, could be made magnetic at low temperatures by introducing a very small number of magnetic atoms. The magnetic atoms they added were manganese, and soon many other "magnetic semiconductors" were discovered. Gallium arsenide, a semiconductor material used for high-performance devices in cell phones, becomes magnetic when manganese is added, but only at a temperature of -88 C (-126 F). In order for it to be used in future computer chips, magnetic semiconductors like gallium manganese arsenide must remain magnetic at higher temperatures and also be made "cleaner," or less resistant to current flow.

"Visualizing the magnetic interactions on the nanoscale may lead to better magnetic semiconductor materials and applications for them in the electronics industry," says Flatté, who along with UI Assistant Research Scientist Jian-Ming Tang predicted that the magnetic interactions could be imaged with a scanning tunneling microscope. "An electron behaves as if it carries a small magnet around with it. This property, called "spin," has not been used in computer chips to date. If the materials are good enough, then new computer chips that require much less power to run are possible. Even revolutionary 'quantum computers' that use strange quantum phenomena of the atomic world to perform calculations may be possible," says Flatté.

Flatté and Tang had predicted that the magnetic interactions should depend strongly on where in the crystal lattice of the semiconductor the atoms were sitting. Some configurations interacted very strongly and others very weakly. "We thought it would require a lot of luck to see this effect. Usually when manganese is placed in gallium arsenide, it enters the lattice in many different positions. To see two manganese atoms within a nanometer of each other, but isolated from all other manganese, would be statistically very unlikely," he says.

Flatté and Tang, theorists, teamed up with experimentalists Professor Ali Yazdani, Dale Kitchen and Anthony Richardella to look for these effects. The experimentalists took a completely different approach toward seeing the magnetic interactions. Instead of trusting luck to help them find an arrangement of atoms, they placed the manganese atoms one at a time into a fresh, clean piece of gallium arsenide. "Using the tip of a scanning tunneling microscope, we can take out a single atom from the base material and replace it with a single metal that gives the semiconductor its magnetic properties," says Yazdani, Princeton University physics professor. He notes that the effort marks the first time that scientists have achieved this degree of control over the atomic-level structure of a semiconductor. In essence, the team used this unique capability to make a semiconductor magnetic, one atom at a time. "The ability to tailor semiconductors on the atomic scale is the holy grail of electronics, and this method may be the approach that is needed," says Yazdani.

Kitchen, a researcher in Yazdani's lab, hit upon the solution while working with a high-tech tool used to explore complex materials called a scanning tunneling microscope, a device that operates very differently from a desktop optical microscope. The device has a finely-pointed electrical probe that passes over a surface in order to detect variations with a weak electric field. The team, however, found that the charged tip could also be used to eject a single gallium atom from the surface, replacing it with one of manganese that was waiting nearby.

By incorporating manganese atoms into the gallium arsenide semiconductor, the team has created an atomic-scale laboratory that can reveal what researchers have sought for decades: the precise interactions among atoms and electrons in chip materials. The team used their new technique to find the optimal arrangements for manganese atoms that enhance the magnetic properties of gallium manganese arsenide. These arrangements agreed with Flatté and Tang's predictions. "To predict how a material will behave, and then have that prediction dramatically confirmed, as in this experiment, is one of the most enjoyable experiences of research," says Flatté.

Flatté cautions that further advances will be required to translate the new research results into new chip technology and also that using a scanning tunneling microscope to grow large pieces of high quality gallium manganese arsenide may not be practical. However, he says, the lessons learned about optimal arrangements of magnetic atoms in semiconductors will be transferred to other semiconductor growth techniques and to other magnetic semiconductor materials.

The research project was funded in part by the National Science Foundation and the U.S. Army Research Office.

STORY SOURCE: University of Iowa News Services, 300 Plaza Centre One, Suite 371, Iowa City, Iowa 52242-2500.

MEDIA CONTACT: Gary Galluzzo, 319-384-0009, gary-galluzzo@uiowa.edu

Gary Galluzzo | EurekAlert!
Further information:
http://www.uiowa.edu

More articles from Physics and Astronomy:

nachricht Space radiation won't stop NASA's human exploration
18.10.2017 | NASA/Johnson Space Center

nachricht Study shows how water could have flowed on 'cold and icy' ancient Mars
18.10.2017 | Brown University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Osaka university researchers make the slipperiest surfaces adhesive

18.10.2017 | Materials Sciences

Space radiation won't stop NASA's human exploration

18.10.2017 | Physics and Astronomy

Los Alamos researchers and supercomputers help interpret the latest LIGO findings

18.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>