

A Microscope That Can See Down to Individual Atoms - DiabloD3
http://motherboard.vice.com/read/this-microscope-can-see-down-to-individual-atoms

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hyperion2010
In case anyone is interested we've been able to do this for quite some time
for TEM and SEM. One big breakthrough for EM lately was the ability to use
direct detectors to look at frozen samples for tomography. With these
techniques we can now reconstruct things like ribosomes all the way down to
their atomic structure [1]. We used to have to use crystallography for this.

1\.
[http://elifesciences.org/content/2/e00461](http://elifesciences.org/content/2/e00461)

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Osmium
> In case anyone is interested we've been able to do this for quite some time
> for TEM and SEM.

Well, not with SEM :) Do you have any more links to other significant cryo-EM
papers btw? Looks incredibly fascinating.

On the non-bio side, the recent major advances have been in aberration-
correction technology. The big limiting factor in electron microscopy has been
aberrations introduced by the electromagnetic lenses used to focus the beam
(and the quality of the electron source itself). We're starting to get past
that, which is good.

The next step seems to be creating a lot more specialised electron
microscopes, rather than just adding multiple detectors to a single
microscope. To use an example, X-rays are also generated due to how the
electron interacts with the sample, and if you detect the X-rays it can tell
us what elements are present. Trouble is, X-rays are emitted in all
directions, and in older microscopes there'd only be room for a single X-ray
detector off to the side, because it also had a bunch of other detectors in
there too, so it'd only capture a fraction of the X-rays emitted. So now
people are realising that if they really want to push the limits of the
technique, they have to create a electron microscope _dedicated_ to, say,
detecting these X-rays, so they can cram as many X-ray detectors around the
sample as they can. This can make the difference between detecting an
unambiguous signal to not detecting one at all, which is incredibly important
when looking at, say, dopants or impurities in semiconductors which exist at
very very low concentrations.

This is just a single example, but there have been many many electron
microscopy-based techniques that have been successfully validated in practice
and can now be taken to the next level by building dedicated, specialised
microscopes.

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hyperion2010
[http://www.nature.com/ncomms/2014/140904/ncomms5808/full/nco...](http://www.nature.com/ncomms/2014/140904/ncomms5808/full/ncomms5808.html)
is another example.

IIRC there are people working on element detection with EELS.

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freshyill
I love that when you get down to this level, things actually look like the
models and diagrams we've all seen before.

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sowhatquestion
Seriously, it's uncanny.

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ph0rque
While in college, I put in dozens of hours on an SEM and got pretty good at
it. A TEM is a whole 'nother story... I would have needed an order of
magnitude (or two!) more training on it to be able to use it proficiently.

~~~
Osmium
> While in college, I put in dozens of hours on an SEM and got pretty good at
> it. A TEM is a whole 'nother story...

For the benefit of anyone who doesn't know, a SEM (scanning electron
microscopy) is an electron microscope that builds an image by scanning an
electron beam across a surface and detecting the scattered electrons. A TEM
(transmission electron microscopy) passes electrons _through_ the material to
detect them on the other side. (Not to be confused is STEM and SEM; STEM is a
scanning variant of TEM, and uses similar equipment, and is equally unlike
SEM.)

The big difference between the techniques is that, once you want to pass the
electron through the sample, _a lot_ changes. First, your electron beam has to
be much higher energy, and your electron source much better quality. This
makes the microscope a lot larger and more expensive. The big thing though is
that suddenly you have to take _extreme care_ preparing your samples. They
need to be thin enough to pass an electron through! So sample preparation is
typically much, much more difficult and painstaking.

TEM is also more advanced in that the interpretation of your images is non-
trivial. With SEM, your image is typically topographic and easier to interpret
(you see what's there), but in TEM which is at much higher resolution, the
many many different ways the electron beam interacts with your sample on the
quantum/atomic-level becomes important, and the contrast you see in your image
doesn't necessarily nicely correspond to a real object. You can also use your
layers of atoms as a diffraction grating and gather information from the
diffraction pattern formed by the electron beam too. So there's a lot going
on.

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mschuster91
So if I read this right, this is 2d only? Could a theoretic 3d scanner with
this resolution be used to e.g. duplicate matter like in a Trek transporter?

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acadien
You can get down a layer two but that's about it. There is no method for
capturing a full 3D model in experiment, although we can get projections from
X-Ray diffraction and other scattering methods. Also there are single photon
X-Ray methods being developed that will get us extremely close to complete 3D
models. But that aside you also have to take into account that these materials
are often not at 0K so they're vibrating or even moving at the atomic scale.
This is a huge problem for example, when studying Proteins.

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Osmium
> There is no method for capturing a full 3D model in experiment

3D atom probe is getting there[1], though that's not at all appropriate for
biological samples. This is where you get a microscopic conical section of
your sample and remove material one layer of atoms at a time using a laser and
then detect the ions removed using a mass spectrometer. This gives a 3D
reconstruction of your sample, which is incredibly useful for crystallography.

[1] [http://www.cameca.com/instruments-for-research/atom-
probe.as...](http://www.cameca.com/instruments-for-research/atom-probe.aspx)

Of course, you can also do tomography with STEM/TEM too, and reconstruct a 3D
model that way. I've seen people do this with analytical EM so you get a 3D
model colour-coded by composition, though this hasn't been at atomic
resolution.

> there are single photon X-Ray methods being developed that will get us
> extremely close to complete 3D models

Do you have a link to some key papers? Sounds fascinating!

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pault
If an atom is mostly empty space, what is being represented by the lighter
valued "blobs" in these images?

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niels_olson
It's roughly the probability of an electron undergoing a state change in the
vicinity. It took a lot of measurements to make those images. It also took a
very sensitive instrument, very good control of high energy particles tuned to
the target, and a very stable local environment (cold, dark, and quiet).

Edit: reviewing awgl's comment: I just want to clarify which electrons we're
talking about. The target has electrons. The electron beam is also, by
definition, electrons. So you're shooting electrons at A) electrons, and B)
nuclei.

What are the odds of a negative, 100 KeV (medium-high energy) electron in the
beam interacting with a heavy, relatively stationary, positively charged
nucleus? High.

What are the odds of a negative, high energy electron interacting with a low-
energy electron that may, occasionally, be in the area? Low.

But we've been shooting high energy electrons at dense targets since the
1920's or 1930's. The joke in accelerators is that most of the particles you
fire miss, implying you can't hit the broad side of a barn. (1)

What's far more impressive is the ability to focus the beam down to sub-
angstrom scale (1^-10 m) and _then scan at equal or higher resolution!_ And
then _detect at the same scale of resolution!_ How? Almost certainly the beam
is steered electromagnetically. I'm interested in the detector. I'm guessing
these are reconstructed using a combination of side-scatter and forward-
scatter information. Not entirely sure how though.

(1)
[http://en.wikipedia.org/wiki/Barn_(unit)](http://en.wikipedia.org/wiki/Barn_\(unit\))

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awgl
I'll readily admit that I'm not a STEM expert. And, honestly, I think I was
conflating the STEM in this article with Scanning Tunneling Microscopy
([http://en.wikipedia.org/wiki/Scanning_tunneling_microscope](http://en.wikipedia.org/wiki/Scanning_tunneling_microscope)).

So, yeah, my comment is not entirely accurate about the electron densities of
the atoms. If you feel it is too misguided, I'll remove it.

This is what happens when you ask a theoretical chemist to explain an
experiment. ;)

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Osmium
> And, honestly, I think I was conflating the STEM in this article with
> Scanning Tunneling Microscopy

It's easy to do. TEM/STEM vs SEM vs STM. All completely different things. This
is what happens when scientists name things :P

For those confused:

TEM/STEM: An electron beam is transmitted _through_ your sample. Good for
atomic-scale imaging.

SEM: An electron beam is scanned across your sample, but none are transmitted
through. Good for topography/surface features (the interaction volume of the
beam is too large for atomic resolution).

STM: No electron beam. Instead think of a vinyl record player, and physically
scanning a very sample tip across the surface of your sample. Good for atomic-
scale imaging of a surface.

A good STM image and a good STEM image can, at first glance, look quite
similar (especially for a 2D material like graphene), but they're very
different techniques.

