“Scanning helium microscope” made it onto ABC News tonight.
world-first-scanning-helium-microscope-unveiled-uni-of-newcastle
Is this, or is this not the same as the scanning helium ion microscope
commercially available since 2007?
If not, how does it work?
SHIM/SHEM?
furious said:
- Is this, or is this not the same
SHIM/SHEM?
the first one can be one of three things. no idea about the second.
The article calls it SHEM and the Wikipedia entry calls it a SHIM…
furious said:
- the first one can be one of three things. no idea about the second.
The article calls it SHEM and the Wikipedia entry calls it a SHIM…
I was only seeing the spacer shim or a tranvestite.
mollwollfumble said:
“Scanning helium microscope” made it onto ABC News tonight.world-first-scanning-helium-microscope-unveiled-uni-of-newcastle
Is this, or is this not the same as the scanning helium ion microscope
commercially available since 2007?If not, how does it work?
“Neutral detection poses a significant technical challenge, one which is further compounded when we use neutral helium – the very properties which make it an ideal probe result in it being the most difficult neutral species to deal with. In general, to detect the neutral atom you must first ionise it, but a typical commercially available detector will only ionise one in every million helium atoms that pass through it. Detection efficiencies so low mean that the SHeM would struggle to collect enough signal to build a decent image. My research centers around developing better ways to ionise the helium, and improving the SHeM geometry to maximise the number of helium atoms capable of being detected.
“FIELD IONISATION
“One of the new approaches to neutral detection is field ionisation (FI). By supplying a large positive voltage to a very sharp tip, a sufficiently large electric field can be established to cause electrons to quantum mechanically tunnel. Any atom within a certain critical radius of the tip will have an electron tunnel out and into the tip, leaving behind a positive ion which may then be easily manipulated and detected. The main limiting factor to field ionisation is the size of the ionisation volume – for a single tip, it is so small that we still only ionise a small portion of the beam. By moving to an array of such tips (each with its own ionisation volume) we can negate this limitation. I look at ways of tailoring carbon nanotubes and other nanoscale arrays for field ionisation, as well how to integrate such arrays into the SHeM.”
How the heck can it be both “neutral” and “ionised”? The two are mutually contradictory.
The following makes more sense. https://www.newcastle.edu.au/research-and-innovation/centre/coe/research/shem/design-of-the-shem
“Using a 10 μm nozzle, a supersonic free-jet expansion of neutral helium is produced in the source chamber. A sharp conical skimmer samples the centreline of the expansion, which then passes into the differential stage. The optics of the instrument consists of a silicon nitride membrane with a milled pinhole mounted into a metal plate. The beam is incident on the back of this membrane, leaving a small spot of helium free to strike the sample. The sample itself is able to be rastered underneath the beam via three linear drives to facilitate imaging. A portion of the helium reflected from each point on the sample surface passes through a second aperture in the pinhole plate into the detector chamber, where the stagnation pressure is sampled to yield the intensity.”
Nice.
The main problem with using electrons for microscopic imaging is that an electric charge builds up on the sample that repels further electrons. The main problem with using ion beams composed of, for example gallium, is that the ion beam is powerful enough to damage the sample. A neutral beam helium microscope would overcome both problems.
That is interesting moll.