New Alternative to Traditional Semiconductors

Researchers from Ohio State University have introduced innovative technology that allows manufacturing plastic computer memory devices. Their invention utilizes the spin of electrons – a known physical phenomenon – to perform reading and writing operations, and it could help produce portable electronic devices.
 The researchers, led by Arthur J. Epstein, devised a prototype plastic spintronic device (Source: Ohio State University)
The researchers, led by Arthur J. Epstein, devised a prototype plastic spintronic device (Source: Ohio State University)

Traditional microelectronics work using transistors, capacitors, and other basic elements; however, new technology – named “spintronics” – could make devices store more data in less space, process data faster, and consume less power.

The new device, created by a team from Ohio State University, was described in a paper published at the August 2010 issue of the journal Nature Materials. The researchers, led by Arthur J. Epstein, devised a prototype plastic spintronic device. Most of the techniques used are readily available in the mainstream computer industry. The possible future benefits led the Air Force Office of Scientific Research, the Department of Energy, the National Science Foundation, and the Office of Naval Research to fund the research.

The device is currently in its initial stages of development; for now, it is little more than a thin strip of dark blue organic-based magnet layered with a metallic ferromagnet (a magnet made of ferrous metal such as iron), connected to two electrical leads. Although the prototype is far from being a fully functional product, the researchers already recorded data successfully – and managed to retrieve it, by controlling the spins of the electrons with a magnetic field.

According to Epstein, the material used is a hybrid of a semiconductor made from organic materials and a special magnetic polymer semiconductor. Due to this mix, it is a bridge between today’s computers and the all-polymer, spintronic computers that he and his partners hope to enable in the future.

This “bridge” could help bypass obstacles faced by regular electronics. The base of today’s common methods is a binary code of ones and zeros, depending on whether an electron is present in a void within the material. However, researchers have long known that electrons can be polarized to orient in particular directions, like a bar magnet. Scientists refer to this orientation as “spin” (either “spin up” or “spin down”) and have been working on a way to store data using spin.

The resulting electronics, dubbed spintronics, hold the future for memory devices, according to Epstein. “Spintronics is often just seen as a way to get more information out of an electron, but really it’s about moving to the next generation of electronics,” he said. It would effectively let computers store and transfer twice as much data per electron, and therefore scientists “could solve many of the problems facing computers today by using spintronics,” said Epstein.

One of the advantages the new technology offers is reduced heat. While typical circuit boards use a lot of energy – in the form of heat created by moving electrons – the spintronic boards would need less cooling. Thus, the limits chipmakers face today, such as how closely they can pack circuits together, will no longer exist.

Epstein explains that flipping the spin of an electron requires less energy and produces hardly any heat at all. It means that spintronic devices could run on smaller batteries; furthermore, if they were made out of plastic, they would also be light and flexible, making the ultimate mobile devices.

“Think about soldiers in the field who have to carry heavy battery packs, or even civilian ‘road warriors’ commuting to meetings,” Epstein said. “If we had a lighter weight spintronic device which operates itself at a lower energy cost, and if we could make it on a flexible polymer display, soldiers and other users could just roll it up and carry it. We see this portable technology as a powerful platform for helping people.”

Epstein and his long-standing collaborator, Joel S. Miller of the University of Utah, present in their study the first organic-based magnet that operates above room temperature. This magnetic polymer semiconductor,vanadium tetracyanoethanide, is, according to Jung-Woo Yoo, a postdoctoral researcher and a team member, an important milestone in spintronic research. “Our main achievement is that we applied this polymer-based magnet semiconductor as a spin polarizer – meaning we could save data on it using a tiny magnetic field,” he said. “It means we could read the data back. Now we are closer to constructing a device from all-organic material.”

Yoo and his Ohio State colleagues layered a sample of conventional magnetic film together with the organic magnet to make a working device. Their demonstration consists of exposing the material to a magnetic field that varied in strength over time. To determine whether the material recorded the magnetic pattern and functioned as a good spin injector/detector, they measured the electric current passing through the two magnetic layers. Not surprisingly, this method is similar to the way computers read and write data to a magnetic hard drive today.

The results were perfect: The team retrieved the magnetic data in its entirety, exactly as they stored it. The patented technology should transfer easily to industry, says Yoo, and claims, “Any place that makes computer chips could do this. Plus, in this case, we made the device at room temperature, and the process is very eco-friendly.”

TFOT has also covered a new compound that may revolutionize chip technology, discovered at Stanford University, and the discovery of magnetic super-atoms, which could increase computers’ memory storage. Another related TFOT story is that of the CPU that stores data, also basing on the spintronics technology.

For more information about the new alternative to traditional semiconductors, see Ohio State University’s press release.

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