Manufacturing Bits: August 18

Making quantum robots
Quantum dots are inorganic semiconductor nano-crystals. The technology can be used to boost the color gamut in LCD TVs. It can also be used in LEDs and other products.

The problem? Quantum dots are expensive to fabricate.

With funding from Dow Chemical, the University of Illinois at Urbana-Champaign has developed a new fabrication process. In doing so, researchers are able to get more light from quantum dots over a large-scale area.

To enable this technology, researchers embedded quantum dots in polymer materials. Then, they used a electro-hydrodynamic jet (e-jet) printing technology. This, in turn, precisely printed the dots on photonic crystal structures. This precision eliminates wasted dots.

To demonstrate the technology, researchers fabricated a 1mm device that resembles a robot. The robot is made of thousands of 6nm quantum dots.

Researchers fabricated a 1mm device (aka Robot Man) made of quantum dots. Every region of the device has thousands of quantum dots, each measuring 6nm (Source: Illinois at Urbana-Champaign)

On the university’s site, Gloria See, a graduate student, said: “We made a tiny device, but the process can easily be scaled up to large flexible plastic sheets. We make one expensive ‘master’ molding template that must be designed very precisely, but we can use the template to produce thousands of replicas very quickly and cheaply.”

Finding quantum dots
Self-assembled, epitaxial-grown quantum dots can also be integrated on a chip for a variety of photonic quantum applications.

The problem? At times, it’s difficult to find the dots. They are just 10nm wide in some cases.

In response, the National Institute of Standards and Technology (NIST) has developed a way to locate quantum dots. Researchers devised a photoluminescence imaging approach for locating single quantum dots.

Basically, NIST uses a camera-based imaging technique. Within the system, there are two LEDs. When the camera flashes, one LED activates the quantum dots.

The second LED illuminates the metallic orientation marks of the dots. Then, the camera snaps a 100-X by 100-micrometer picture. The glowing dots are cross-referenced with the orientation marks. Then, the dots can be located with an uncertainty of less than 30nm.

“This is a first step towards providing accurate location information for the manufacture of high performance quantum dot devices,” said NIST physicist Kartik Srinivasan, on the agency’s Web site. “So far, the general approach has been statistical—make a lot of devices and end up with a small fraction that work. Our camera-based imaging technique maps the location of the quantum dots first, and then uses that knowledge to build optimized light-control devices in the right place.”

More GaN
Imec is expanding its gallium nitride-on-silicon (GaN-on-Si) R&D program.

The R&D organization is offering joint research on GaN-on-Si 200mm epitaxy and device technologies. The process line is also open to fabless companies. The extended R&D initiative includes exploration of novel substrates to improve the quality of the technology.

GaN-on-Si enables a new wave of LEDs and power chips. GaN technology enables faster switching power devices with higher breakdown voltages. “Since the program’s launch in July 2009, we have benefited from strong industry engagement, including participation from IDMs, epi vendors and equipment and material suppliers,” said Rudi Cartuyvels, executive vice president of smart systems at Imec, on the organization’s Web site. “Interested companies are invited to become a partner and actively participate in our program. Imec’s open innovation model allows companies to have early access to next-generation devices and power electronics processes, equipment and technologies and speed up innovation at shared cost.”