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 Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory

nachricht SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute

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: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Bare bones: Making bones transparent

27.04.2017 | Life Sciences

Study offers new theoretical approach to describing non-equilibrium phase transitions

27.04.2017 | Physics and Astronomy

From volcano's slope, NASA instrument looks sky high and to the future

27.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>