Transistors - Page 3

Scientists who dream of shrinking computers to the nanoscale look to atomic spin as one possible building block for both processor and memory, yet setting the spin of an atom, let alone measuring it, has been a challenge.

Now, University of California, Berkeley, physicists have succeeded in measuring the spin of a single atom, moving one step closer to quantum computers and "spintronic" devices built from nanoscale transistors based on atomic spin.

Crommie, UC Berkeley post-doctoral fellow Yossi Yayon and graduate student Victor W. Brar succeeded by creating islands of cobalt atoms on a cold copper substrate (4.8 Kelvin, or -451 degrees Fahrenheit) and sprinkling these islands with atoms of either iron or chromium.

Employing a relatively new technique called low-temperature spin-polarized scanning tunneling spectroscopy - essentially a scanning, tunneling microscope that can probe the spin and energy-dependent electron density of a surface - they were able to determine the spin of isolated adatoms atop these cobalt nanoislands.

Read more here (UCBerkeley news) 

 

IBM has linked with Japan's TDK to develop so-called spin torque transfer RAM (random access memory) or STT-RAM. In STT-RAM, an electric current is applied to a magnet to change the direction of the magnetic field. The direction of the magnetic field (up-and-down or left-to-right) causes a change in resistance, and the different levels of resistance register as 1s or 0s.

Under the current plan, IBM and TDK, an integral player in magnetic recording components for hard drives, will develop a 65-nanometer prototype within the next four years.

Previously, IBM had been working on a more conventional type of magnetic memory called MRAM. However, the company has been having trouble shrinking the transistors on these chips.

Electronic devices are always shrinking in size but it's hard to imagine anything beating what researchers at the University of New South Wales have created: a tiny wire that doesn't even use electrons to carry a current.

Known as a hole quantum wire, it exploits gaps – or holes - between electrons. The relationship between electrons and holes is like that between electrons and anti-electrons, or matter and anti-matter.

The holes can be thought of as real quantum particles that have an electrical charge and a spin. They exhibit remarkable quantum properties and could lead to a new world of super-fast, low-powered transistors and powerful quantum computers.

Associate Professor Alex Hamilton and Dr Adam Micolich, who lead the UNSW Quantum Electronic Devices group in Sydney, Australia, say the discovery that the holes can carry an electrical current puts the team at the front of its field in the quantum electronics revolution.

Quantum wires are microscopically small, in this case about 100 times narrower than a human hair. They are so narrow that electrons can only pass along them in single file.

Manufacturers are keenly interested in them because they hold the potential for new high-speed electronics applications, known as spintronics, where semiconductor devices have both electric and magnetic properties.

Electrons have both electric (charge) and magnetic (spin) properties but today's micro-chips use only the charge properties of electrons.

"To move ahead with spintronics, we need to be able to control the magnetic properties with electronics," says Professor Hamilton.

"Quantum holes also have spin, and this can be strongly affected by electric impulses. So semiconductors that use holes, rather than electrons, would be good for spintronics and quantum information technologies that use spin to store and process data." 

Read more here 

Researchers at the University of Bath have received new funding to investigate how the emerging field of spintronics can be applied to in-chip communications, they announced Friday.

Spintronic techniques are already used in some hard disk drives as a way to increase the density of stored information. Spin control also plays a role in the storage of information in MRAM magnetic memories, and in the manipulation of data in quantum computers, another emerging application of spintronics.

However, the researchers at Bath are interested in applying spintronics to the transmission of information, not its storage or manipulation.

The transistors used in today's microprocessors could run at speeds of up 100GHz if it weren't for the wires connecting them to one another, according to Alain Nogaret, a lecturer in the department of physics at Bath.

As processors run at higher and higher frequencies, wires present an obstacle to electrical signals, rather than an unobstructed path, so the signals quickly fade away, even over short distances: "The limit is not the transistors, but the losses in the electronic signals between transistors or clusters of transistors," Nogaret said.
"One way to cut these losses is to send these signals through microwaves," he said. In that way, the signal loss at 100GHz can be cut to just a couple of decibels per centimeter from 115 decibels per centimeter along a wire, he said.

Nogaret and his team hope to generate those microwaves by applying a theory he published in Physical Review Letters last year, entitled "Electrically induced Raman emission from planar spin oscillator," in which he predicted that radio signals are emitted when the spin of an electron trapped in a magnetic field resonates with that field.

Once the research is complete, Nogaret predicts that it will take another five to 10 years before the technology appears in production chips.

Although we can’t pin down the exact date for the funeral, silicon chips are set to die out just as bipolar transistors did some 25 years before them. And with their death, the era of spintronics will truly be born...

Which brings us to the future. Whereas traditional electronic circuits transport charge carriers – electrons – through a conductor, spintronic circuits harness a different property of electrons to do more work with less effort.