R&D
The technique uses the different relative dielectic
constants of the two types of tube with respect to the solvent. Using
alternating current dielectrophoresis, the two types of tube move in
opposite directions along the electric field gradient. The metallic tubes
are attracted towards a microelectrode array leaving the semiconducting ones
in the solvent.
The effectiveness of the separation was tested using Raman spectroscopy. It
is estimated that 80% of the deposited tubes are metallic with a 5% error.
The original suspension is assumed to contain 33% metallic tubes.
The scientists believe that in principle a complete separation is possible
if all tubes in the suspension are present as individual tubes and not
bundled as is often the case. A metallic tube in a bundle of semiconducting
is also attracted to the electrodes. In fact, the team used a four-hour
preparation technique to boost the number of individual tubes before using
their ten-minute dielectrophoresis process.
The team estimates that some 100pg of metallic tubes are deposited out of
roughly 100ng in the drop. This is too small to see a depletion of metallic
tubes in the suspension.
"However," the report concludes, "we are confident that the separation
method can be substantially upscaled by the use of microfluidic
dielectrophoretic separation cells as commonly used in biology."
Scientists from California company Xradia and from Stony Brook university in
New York propose using achromatic Fresnel optics for focusing exteme
ultraviolet (EUV) and x-ray light (Nature, July 3, 2003). The design
combines a Fresnel zone plate with a refractive lens having the opposite
chromatic aberration. A Fresnel zone plate consists of concentric rings put
on the surface of a material that phase shifts light to produce a focus.
Fabrication is made possible by using the large anomalous dispersion of the
lens material near an absorption edge.
The scientists claim that the resolution is comparable to Fresnel zone
plates that have achieved the highest resolution so far (25nm) in the entire
electromagnetic spectrum. However, the new system achieves an improvement in
spectral bandwidth of two or more orders of magnitude. This means that there
would be less need for narrowing the spectral width of the light. Lower
power sources could be used to produce comparable throughputs.
The team sees applications for x-ray microscopy and microanalysis and
next-generation lithography.
AngelTech Live III: Join us on 12 April 2021!
AngelTech Live III will be broadcast on 12 April 2021, 10am BST, rebroadcast on 14 April (10am CTT) and 16 April (10am PST) and will feature online versions of the market-leading physical events: CS International and PIC International PLUS a brand new Silicon Semiconductor International Track!
Thanks to the great diversity of the semiconductor industry, we are always chasing new markets and developing a range of exciting technologies.
2021 is no different. Over the last few months interest in deep-UV LEDs has rocketed, due to its capability to disinfect and sanitise areas and combat Covid-19. We shall consider a roadmap for this device, along with technologies for boosting its output.
We shall also look at microLEDs, a display with many wonderful attributes, identifying processes for handling the mass transfer of tiny emitters that hold the key to commercialisation of this technology.
We shall also discuss electrification of transportation, underpinned by wide bandgap power electronics and supported by blue lasers that are ideal for processing copper.
Additional areas we will cover include the development of GaN ICs, to improve the reach of power electronics; the great strides that have been made with gallium oxide; and a look at new materials, such as cubic GaN and AlScN.
Having attracted 1500 delegates over the last 2 online summits, the 3rd event promises to be even bigger and better – with 3 interactive sessions over 1 day and will once again prove to be a key event across the semiconductor and photonic integrated circuits calendar.
So make sure you sign up today and discover the latest cutting edge developments across the compound semiconductor and integrated photonics value chain.
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