
Probing quantum phenomena in tiny transistors - dnetesn
http://phys.org/news/2016-07-probing-quantum-phenomena-tiny-transistors.html
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analognoise
Can we pattern the nanowires like we do silicon, or is alignment more
difficult?

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jeffwass
I dealt quite a bit with nanowires during my PhD research a decade ago.

E-beam lithography can be used for features this small but it's more for one-
offs as in academic research like this. It's not an industrial scalable
solution for high-capacity production.

Optical lithography works well for industry, but the wavelengths are larger so
it's hard to pattern structures this small. Though by pushing wavelengths
further into the UV and doing tricks to compensate for diffraction, optical
lithography has also come a long way in terms of feature resolution and may be
a potential solution. I'm not up-to-date on the current state of the art.

In my lab, one technique we used involved carbon nanotubes lying as a bridge
over a trench, over which we'd deposit superconducting alloys. This was a way
to create nanowires about 10nm wide, allowing us to study superconductivity in
one dimension.

But you're right in that alignment was difficult. We'd basically put an
optimally-dense suspension of carbon nanotubes in a fluid on the substrate and
hope that some would cross the trench, find them in a SEM after applying the
superconducting alloy.

They're also super delicate, so we had to hope we didn't blow them up with
tiny static charges while patterning the leads, wire-bonding the silicon
substrate to a chip carrier, connecting to our wired cryostat, and evacuate
/cool them down to cryogenic temperatures. Felt a bit like Edison and first
light bulb attempts!

One of my lab colleagues was studying the physics of the carbon nanotube
itself, and interesting things that could happen with magnetic leads in
magnetic fields (aligning electron spins). Once he had a working sample it
stayed in the dewar for over a year as he studied different aspects of it!

