Plastic spin transistors come closer to reality

London, August 18 : Researchers at the University of Utah have achieved a significant success in controlling an electrical current using the "spin" within electrons, which they say brings the realisation of a plastic semiconductor switch for future ultrafast computers and electronics a step closer to reality.

The researchers say that their study, however, shows that it will be more difficult than thought to make highly efficient light-emitting diodes (LEDs) using organic materials.

According to their findings, such LEDs would convert not more than 25 percent of electricity into light rather than heat, contrary to earlier estimates of up to 63 percent.

Lead researchers Christoph Boehme and John Lupton, assistant and associate professors of physics, have revealed that their advancement springs from an experiment that merged organic semiconductor electronics and spin electronics, or spintronics, which is part of quantum mechanics - the branch of physics that describes the behavior of molecules, atoms and subatomic particles.

"This is the first time anyone has done really fundamental, hands-on quantum mechanics with an organic LED. This is tough stuff," Nature magazine quoted Lupton as saying.

An atom includes a nucleus of protons and neutrons, and a shell of orbiting electrons. In addition to an electrical charge, some nuclei and all electrons have a property called "spin", which is like a particle's intrinsic angular momentum.

An electron's spin often is described as a bar magnet that points up or down, which can represent a binary code of ones and zeroes in computing.

Lupton says that physicists already have shown that spins can carry information in nonorganic materials, and that a team of Utah physicists had announced in 2004 the creation the first organic "spin valve" to control electrical current.

In their latest study, the researchers demonstrated that information could be carried by spins in an organic polymer.

Lupton says that a spin transistor is was possible because "we can convert the spin information into a current, and manipulate it and change it."

"We are manipulating this information and reading it out again. We are writing it and reading it," he adds.

Boehme says that spin transistors and other spin electronics may make possible much smaller computer chips, and computers that are orders of magnitude faster than today's.

"Even the smallest transistor today consists of hundreds of thousands of atoms. The ultimate goal of miniaturization is to implement electronics on the scale of atoms and electrons," says Boehme.

As regards LEDs made of electrically conducting organic materials, the researchers said that they were cheaper and easier to manufacture, though their efficiency was long thought to have an upper limit of 25 percent.

In their research paper, the researchers insisted that 25 percent efficiency might be correct at least for the organic polymer studied, pure MEH-PPV, and possibly for others.

However, Boehme insisted that organic LEDs' greatest promise was not in lighting, but to replace the LCD (liquid crystal display) technology in modern televisions and computer screens.

He said that organic LEDs would be much cheaper, could be made on flexible materials, had a wider viewing angle and colour range, and would be more energy efficient than LCDs.

ANI