Slashdot Mirror
New Type of Atomic Microscope On the Way
Iddo Genuth writes "Researchers at the Surface Science Laboratory at Universidad Autonoma de Madrid have created an ultrasmooth mirror that could be used to create a revolutionary new atomic microscope within the next several years. The new atomic microscope — using helium atoms for imaging — has the potential to provide the same resolution as existing electron microscopes but without many of the problems which have plagued them for years."
It's not already done at all - the techniques are quite distinct, they just have the word helium in them. All the work on helium ion microscopes I've seen uses ions well into the kV range. The resolution is definitely improved...but you're still firing things at a surface with thousands of times more energy than a chemical bond, and helium ions have a lot more mass than electrons. What does spewing electrons even mean anyway? They get focussed the same way as helium ions, after all...
The neutral atom microscope projects work with beams in the meV (that's *milli* eV) range. The atoms rebound a few angstroms from the 'surface', the beam is produced using a supersonic free jet expansion, the focussing is done differently...it's a completely different microscopy technique.
This isn't a new type of microscope, this is actually kind of old. I was working in a lab doing this as an undergrad in 94. It really only works with very smooth (as in atomic level smooth) crystalline structures. You can build 3-d data, that's for sure, but only by growing them and watching them build as you shoot helium at it (via rotating the mirror and watching the diffraction). Purely surface chemistry "simple" crystals. Unless for things like protein structures, where X-ray is the way to go.
What these guys did was merely figure out a way to reflect helium better, so you get more exact data the first time around, rather than having to run the same test over and over and doing averages to get rid of the noise. Good for science, sure, but hardly a new microscope.
Burn Hollywood Burn
Yep, the idea is to use neutral atoms. Actually people tend to get a bit hung up on the resolution issue - it is true that it is an absolute pain to both focus and detect neutral helium, and other microscopies offer better ultimate resolution. ;o) ) but that's not really the point.
However, what things like helium ion microscopy and scanning electron microscopy don't offer is absolute surface sensitivity, with almost no damage. An SEM can only be used with conducting samples (yes, you can gold or graphite coat stuff but if you're interested in the surface you're still stuffed) and the beam penetrates a good 30-100 atomic layers so the *surface* resolution is quite limited. Helium ion microscopy is better in that regard but still penetrates quite a few atomic layers and will still damage the surface.
In short, if you're interested in delicate or reactive surfaces, neutral helium is probably the only way to go. The initial resolution won't be great (I believe they're still aiming initially for sub-optical, rather than atomic
Ignorance is OK. Not reading the article before posting is ... Slashdot.
Here, let me help you:
The high speed electrons used in the electron microscope <nah nah nah> making it difficult to get accurate results and impossible to repeat tests.
I'm sorry if I haven't offended anyone
The group working at Cambridge has a detailed description: http://www-sp.phy.cam.ac.uk/research/mirror.php3 I was a little surprised to read this as being new. Although the He microscope, as it is envisioned, has not yet been built, the Cambridge group has been working on the idea for a while. I'm not sure how much of an improvement the techniques of the group in the story are - for producing flat mirrors - than what is already being used at Cambridge. The Si surfaces they use are already pretty flat. As far as I understood it the most critical area for development was the detector.
Conservation of angular momentum makes the world go round.
Because of this:
That was one of the most funny /. postings, indeed.