semiconductor
Just as the Microtechnology Age was built upon the introduction of impurities into crystals of semiconductor materials, so, too, will crystalline doping be the bedrock upon which the Nanotechnology Age is built. To advance the arrival of this next technological era at a faster pace, however, scientists need a better understanding of what happens to nano-sized crystals under the various forms of doping.
Physicists have built a critical component for the development of quantum computers and spintronic devices, potentially bringing advances in cryptography and high-speed database searches a step closer. A team of researchers has created a device that can effectively split a stream of quantum objects such as electrons into two streams according to the spin of each, herding those with ''up'' spin in one direction and corralling those that spin ''down'' in another. By producing such ''spin-polarized'' streams, the tiny device could become a key component in quantum computers, which have not yet left the drawing boards of the computer industry but are highly sought-after for their purported facility at cracking codes and searching large databases.
Until now, lightweight plastic solar cells have remained elusive. During the last decade, scientists have struggled to substitute polymers for the expensive, but effective crystalline materials such as silicon, a traditional solar cell material. These attempts produced solar cells with poor efficiencies at converting light into electricity. Researchers now hope to develop an improved polymer solar cell using nanomaterial additives. Specifically, a team in Rhose Island will use a thin polymer film that can be rolled out in sheets. The film will contain nanoscale pieces of semiconductor material and single-walled carbon nanotubes to maximize energy conversion.
Researchers have developed an improved method for directly writing nanometer-scale patterns onto a variety of surfaces. Infrared microscope image shows a cantilever during heating. The colors correspond to temperature, the hottest reaching approximately 200 degrees Celsius. The microcantilevers are engineered such that the temperature increases only near the free end. The new writing method, dubbed ''thermal dip pen nanolithography,'' represents an important extension for dip pen nanolithography (DPN), an increasingly popular technique that uses atomic force microscopy (AFM) probes as pens to produce nanometer-scale patterns.
A significant breakthrough in the development of the highly prized semiconductor gallium nitride as a building block for nanotechnology has been achieved by a team of scientists with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley. For the first time ever, the researchers have been able control the direction in which a gallium nitride nanowire grows. Growth direction is critical to determining the wire's electrical and thermal conductivity and other important properties.
A research team at Rensselaer Polytechnic Institute has created a new type of reflector that has dramatically improved LED (light-emitting diodes) luminance. The National Science Foundation (NSF) recently awarded the research team a three-year, $210,000 grant to move the patented omni-directional reflector to market. ''We have developed an omni-directional reflector for LEDs that will accelerate the replacement of conventional lighting used for a multitude of applications, such as lighting in homes, businesses, museums, airports, and on streets,'' said Fred Schubert, Wellfleet Senior Constellation Professor of the Future Chips Constellation at Rensselaer who is heading the research effort.
Scientists at Lawrence Berkeley National Laboratory have found new ways of combining quantum dots and segmented nanorods into multiply branching forms and have applied new ways to calculate the electronic properties of these nanostructures, whose dimensions are measured in billionths of a meter.
A wireless nanodevice that functions like a fluorescent light - but potentially far more efficiently - has been developed in a joint project between the National Nuclear Security Administration's Los Alamos and Sandia national laboratories. The experimental success, reported in the June 10 issue of Nature, efficiently causes nanocrystals to emit light when placed on top of a nearby energy source, eliminating the need to put wires directly on the nanocrystals.
''Waste heat'' might not be such a waste after all. The excess heat produced in everything from microelectronics to large ship engines is generally thought of as a problem for engineers to solve. But a new leap in semiconductor technology funded by the Office of Naval Research could put that troublesome heat to good use.
A new breed of faster, more powerful computers based on quantum mechanics may be a step closer to reality, report scientists. By linking a pair of tiny ''puddles'' of a few dozen electrons sandwiched inside a semiconductor, researchers have enabled these two so-called ''quantum dots'' to become parts of a transistor -- the vital switching component in computer chips. Future computers that use quantum dots to store and process digital information might outperform conventional computer circuits because of both the new transistors' smaller size and their potential to solve problems that would take centuries on today's machines.
A warm winter coat doesn't work nearly as well if it's full of holes. The same is true for hafnium oxide, a promising insulator for the next generation of smaller, faster microchips. While hafnium oxide prevents currents from leaking through the ultrathin layers of semiconductor chips more than 1,000 times better than conventional silicon oxide, its prospects have been dampened by too many current-draining defects. Now a team of National Institute of Standards and Technology (NIST) and IBM researchers reports in the March edition of Electron Device Letters that they have quantified these "electrical capture defects" in a way that may help chipmakers reduce the defects or at least devise a way around them.
"Nature was nano before nano was cool," stated Henry Fountain in a recent New York Times article on the proliferation of nanotechnology research projects. No one is more aware of this fact of nature than Dan Morse of the University of California, Santa Barbara. His research groups have been studying the ways that nature builds ocean organisms at the nanoscale for over ten years. They have studied the abalone shell for its high-performance, super-resistant, composite mineral structure. Now they are now looking to learn new biotechnological routes to make high performance electronic and optical materials.
In a major advance for cryogenics, researchers at the National Institute of Standards and Technology (NIST) have developed a compact, solid-state refrigerator capable of reaching temperatures as low as 100 milliKelvin. The refrigerator works by removing hot electrons in a manner similar to an evaporative air-conditioner or "swamp cooler."
Electricity moves across miles in seconds to power manufacturing and utilities nationwide. But, for all its speed, the loss of just fractions of seconds of electric power is costing the U.S. economy $100 billion a year. "The nation's electric grid is operating so close to capacity that many of today's electric load demands for fast and dynamic voltage support cannot be provided fast enough," says Alex Huang, professor of electrical and computer engineering at Virginia Tech. To solve the problem, Virginia Tech researchers have developed a high-power semiconductor switch. The invention has earned a 2003 R&D 100 Award from R&D Magazine.
A method that can be used to predict the growth of earthquake faults also aids prediction of the tiniest of phenomena--how arrays of "artificial atoms," or quantum dots, assemble and stack themselves on semiconductor materials, National Institute of Standards and Technology (NIST) researchers report in the July 15 issue of Physical Review B.
