news digest ♦ LEDs
light in at an angle and greatly increases the space occupied by apparatus
“With the new design, the illumination will be applied directly over the probe tip at the same place on the sample that is being exposed to the microwave signal. That could be particularly beneficial in characterising photovoltaic materials where you could apply a light and get the carrier concentration at the same time. The whole unit can be much smaller, and the nanoscale light source enables you to inject some carriers very locally, in a way you can’t do with other methods.”
In order to research the next generation of photovoltaic materials, Bertness says, “We’ve been using flood illumination. But what we want to see is how individual grains respond to light. The LED technique can make that possible. In biological applications, we expect it to provide an order of magnitude improvement in the ability to investigate processes such as protein dynamics.”
Reaching that goal will require more research into how to dope the GaN nanowires so as to increase efficiency of light output, and how to coordinate and integrate measurements from topographic, microwave, and optical modalities.
But Bertness is optimistic. He says, “It took ten years of hard work learning how to fabricate and characterise these materials, and we developed a lot of important metrology techniques along the way. But we really weren’t able to test nanowires as probe tips until a few months ago when the Boulder lab’s Precision Imaging Facility gained a focused ion beam. These initial results give us confidence that this technology will impact a broad range of science and technology problems where knowing the properties of materials on the micrometer and nanometre scale is crucial, from semiconductor electronics to biochemistry and medicine.”
The International Technology Roadmap for Semiconductors (ITRS), a periodic assessment of the semiconductor industry’s future technology requirements, has repeatedly called for progress in this area.
The 2011 ITRS believes, “There is a need for characterising the structure and local properties of current CMOS devices as they scale down… Recent developments in Scanning Probe Microscopy involving frequency-dependent signals on the sample and tip, and simultaneous perturbation with more than one frequency and/or probe expand the range and resolution of the measurements.”
The 2013 edition comments, “Commercial vendors have developed a large toolbox of specialized SPM cantilevers and tips. Reproducibility is often an issue; in some cases yields of good tips are on the order of 30%. More important is the gap between commercially available cantilevers/tips and those required for tool development. … The lack of calibration standards for nm sized physical structures is a significant problem.”
Osram Duris S 5-LEDs have a CRI over 90
The two new III-nitride based LEDs are suited for general illumination and solid state lighting
Osram Opto Semiconductors has added two further models with excellent colour rendering to the Duris S 5 family. The new LEDs are ideal for the home, for example installed in downlights or LED retrofit lamps.
Osram Duris S 5 LED
“The Duris portfolio has been expanded with the addition of two new LEDs with an impressive CRI of more than 90. This product family now offers customers even greater flexibility in terms of performance, areas of application and technology than ever before,” says Janick Ihringer, Product Manager for General Illumination at Osram Opto Semiconductors.
The previous Duris S 5 versions already had a high colour rendering index of more than 80, but the additions are even better in this respect.
The new LEDs are ideal particularly for applications where the colours have to appear as natural as possible. Their main use will therefore be in the home. The light from the new Duris S 5 models make the colours of wooden dining tables and flooring for example look rich and natural. Natural colour rendering also plays an important role in shop lighting, whether for clothing or food.
The new Duris S 5 also offers impressive output. The two-chip version has a high luminous flux value of 83 lm at 150 mA (typically at 3000 K). Its typical forward voltage is 6.35 V.
The E, P and S Duris series contain LED versions in different qualities of light and for all output ranges (high-power, mid- power, and low-power) which are suitable for numerous lighting applications.
A robust plastic package, a compact design and a particularly homogeneous distribution of light are other properties common to all members of the family. All the products in the Duris S range also have an impressive price performance ratio, coupled with enormous versatility and efficiency.
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www.compoundsemiconductor.net June 2014
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