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Over the Horizon: Nanoglue, Efficient solar cells, Molecular Memory and Silica Microwires

22 March 2013

Every month, Electronics360 Contributing Editor Abe Michelen surveys academic and technical journals to uncover promising research that will impact the development of “over the horizon” commercial products that could well impact our lives in the future. This month's theme is applications of nanotechnology.

Heat transfer in semiconductors: Nanoglue boosts heat transfer

A team of researchers at Rensselaer Polytechnic Institute (RPI) in Troy, New York, has developed an innovative method to increase the heat transfer capabilities between two materials. This discovery, which was reported in the Rensselaer Alumni Magazine of Fall 2012 could enable new powerful ways to cool computer chips and light emitting diodes (LEDs) and could speed the development of more efficient ways to collect solar energy, among other things.

Heat transfer is a critical aspect of modern electronics. As computer chips become smaller and more complex, manufacturers are looking for new ways to remove excess heat from semiconductor devices to increase reliability and performance.

Led by Professor of Materials Science and Engineering Ganpati Ramanath, the RPI team sandwiched an ultrathin material they call “nanoglue” between copper and silica. At the end of the experiment they found that this arrangement provided a four-fold increase in thermal conductance at the interface between the two materials. The nanoglue is one nanometer (or less) thick and is formed by a single layer of molecules that form strong links with the copper (a metal) and the silica (a ceramic), which otherwise would not stick together well. This is another example of the potential nanotechnology will play in the future of the semiconductor industry.

Renewable energy: Efficient solar cells

In a recent article in Nanowerk, researchers from Lund University in Lund, Sweden, have shown how nanowires could pave the way for more efficient and cheaper solar cells, by reporting a stunning 13.8 percent efficiency rate for nanowire solar cells. No research to date has shown a result above 10 percent.

“Our findings are the first to show that it really is possible to use nanowires to manufacture solar cells,” said Magnus Borgström, principal author of the research, and professor in semiconductor physics at Lund University.

Nanowires are made of the semiconductor material indium phosphide and, when assembled, absorb sunlight and generate power. The researchers assembled four millions nanowires in one square millimeter. The nanowires act like antennae and absorb solar energy like an RF or microwave antenna absorbs radio signals and generates energy.

Borgström’s team demonstrated a nanowire solar cell arrangement that produced several times more energy per surface area than conventional solar cells. Today nanowire solar cells are in development but so far have not been able to be used commercially because of the very low efficiency achieved. The hope is that this technology could be used in large solar power plants in sunny regions such as the southwestern USA, southern Spain and Africa.

Molecular Memory heralds New Data Storage

An MIT team of researchers in the Department of Physics, led by Jagadeesh Moodera, have developed a new technology to store data they call “molecular memory.” The technology, which was reported in MIT News, stores data in individual molecules known as graphene fragments at room temperature. The graphene molecules consist largely of flat sheets of carbon, which are attached to zinc atoms attached to zinc atoms. This makes them easier to align during the manufacturing process.

The technology to use single molecules to store data is not new, but previous attempts requires the use of two ferromagnetic electrodes to confine the molecules. The new MIT technology requires only one ferromagnetic electrode, which will simplify the manufacturing process. Another advantage of this technology is the fact that the graphene fragments are contained in flat sheets of graphene that can be deposited in very thin layers with precise positioning, simplifying further the manufacturing process.

The normal process of using two ferromagnetic electrodes to store data in molecules consists of changing the relative magnetic orientation of the two electrodes, a situation that produces an increase in the conductivity of the molecules. The two states of conductivity represent the 1’s and 0’s of data in binary logic.

Moodera’s group found that the same two states of conductivity can be created with only one ferromagnetic electrode. “The ability to alter the molecule’s conductivity with only one electrode could drastically simplify the manufacturing process of molecular memory,” said Moodera

Self-Assembled Silica Microwires

An international team of researchers from Australia and France developed a method to produce silica microwires by “coaxing” silica nanoparticles to self-assemble into highly uniform silica wires. The researchers describe the manufacturing technique and its potential applications in the last issue of the Optical Society’s journal Optical Materials Express.

According to the authors, this method of self-assembling will allow silica – in the form of microwires – to combine with any material. This is significant because silica is normally incompatible with most other materials.

“We’re currently living in the ‘Glass Age,’ based upon silica, which enables the Internet,” said John Canning, team member and a professor in the school of chemistry at The University of Sydney, New South Wales, Australia. “Silica’s high thermal processing, ruggedness, and unbeatable optical transparency over long distances equate to unprecedented capacity to transmit data and information all over the world.”

However, when bridging the gap between optical fiber (silica), transmitting data at light-speed, and the electronic and photonic components – such as switches, sensors, optical circuits - present in all networks requires some form of interconnect. The interconnection losses, however, are enormous making it one of the most important issues not already resolved in optical communications.

If the silicon microwires can be manufactured by self-assembly they could be combined with practically any material at the moment of manufacturing, and they would be the perfect materials to produce efficient interconnects that will not slow the transmission of data through the fiber.

To contact the author of this article, email abe.michelen@ieeeglobalspec.com


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