Manufacturing Bits: July 19

Detecting anapoles; testing nanowires.


Detecting anapoles
A*STAR has detected invisible particles. Researchers from the Singaporean R&D organization have observed a new optical effect in nanoscale disks of silicon, which are patterns of radiation that do not scatter light.

One example of a non-radiating source is called an anapole. An anapole, according to A*Star, is a distribution of charges and currents. They do not radiate with external electromagnetic fields.

Some sub-atomic particles exhibit anapole modes. These modes are a potential source of dark matter. Dark matter accounts for 25% of the mass and energy of the universe.

An anapole mode is a combination of two dipole moments. This includes the electric dipole moment and a toroidal moment.

A*STAR and others have demonstrated the existence of anapole radiation modes in the lab. Researchers observed the spectral overlap from the anapole mode through a technique called geometry tuning. “For such modes, energy does not escape from the nanoparticle through radiation or scattering. And when the nanoparticle is excited by anapole light excitation, it does not scatter the light since it concentrates the energy at close distances and is invisible at long distances,” said Yefeng Yu, a researcher from the A*STAR Data Storage Institute.

“Applications of this optical phenomenon have yet to be determined,” Yu said. “At the moment, we think that it could be useful for the design of novel nanolasers.”

Testing nanowires
The University of California at Irvine (UCI) has devised a new method for analyzing nanowires at temperatures approaching 700 degrees Kelvin.

Researchers developed a system based on a customized version of a vacuum chamber and related equipment. As it turns out, the system melted the wire coatings and destroyed the adhesives that bonded nanowire-based chips to their holders. So, researchers devised new heat-tolerant wiring and screws, as well as a new mounting platform.

With the system, the measurements were taken on smooth silicon nanowires at 40nm to 120nm. Researchers observed the optical phonons as the diameters decreased and the temperatures increased in the nanowires.

“Our work verifies what engineers have long expected: that certain materials would have good thermoelectric properties at the nanometer scale even at high temperatures,” said Jaeho Lee, UCI assistant professor of mechanical and aerospace engineering, on the university’s Web site.

UCI materials scientist Allon Hochbaum added: “(The) new work develops the ability to measure the thermal conductivity of nanoscale materials at higher temperatures than was previously possible. This allows for the characterization of promising high-temperature thermoelectric substances, such as silicon nanowires, under conditions similar to their optimal operating temperature.”

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Detecting zeptojoules; combo inspection tool; FIB lab.

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