Talk:Transmission electron microscopy

Comment

12:27, 4 December 2005 Average Earthman > Gives the wrong impression - you don't need a monochromator to do EELS.

So please give an example! Or do you mean, I should have followed Electron spectrometer and say spectrometer? But how come, most EELS images are color images, one color for each element. No spectrum.--Arnero 19:47, 6 December 2005 (UTC)

Well, a spectrometer is in a sense also a monochromator. But I believe the point Average Earthman was trying to make was that you do not need a monochromatic incident electron beam in order to perform EELS. Of course, the more monochromatic the incident beam is, the higher the energy resolution that can be obtained in the energy loss spectrum. You do, of course, need some sort of post-specimen spectrometer.O. Prytz 15:15, 18 December 2005 (UTC)

Thanks, I moved on to Energy Filtered transmission Electron Microscopy. --Arnero 18:13, 18 December 2005 (UTC)

Someone has included a sentence about "RTPEM" technique at the end of "applications of.." does anyone know what RTPEM is? O. Prytz 14:22, 26 December 2005 (UTC)

Never heard of it (yet). I don't think we should just have swathes of acronyms with no explanation or suggestions for further reading, so until we get some citation to a journal paper and expansion of this I don't think it belongs here and have deleted it. I tried a quick google and searched on a couple of journals, but can't find anything from just the acronym. Average Earthman 15:33, 26 December 2005 (UTC)

I agree. I also tried a quick search and nothing turned up. Let's see if that editor comes back with an expanation.O. Prytz 15:56, 26 December 2005 (UTC)

It has exactly one search result at Google Scholar. This is certainly a non-notable, if not self-serving, link. eaolson 17:04, 26 December 2005 (UTC)

If the search results on Google scholar were the ones I've seen, they're a particular sequence of amino acids and something to do with lepton-hadron reactions. Not promising leads if you are looking for a TEM application. Of course, he may have meant "RPTEM", but that's no better. Average Earthman 22:16, 26 December 2005 (UTC)

Merging?

It has been suggested that selected area diffraction be merged into this article. I think the content of that article is too detailed to be included into this one, so I'm removing the tag. However, we might consider expanding this article with a brief section on diffraction in TEM, with links to the electron diffraction and selected area diffraction articles. O. Prytz 23:40, 11 March 2006 (UTC)

I still feel that the selected area diffraction article is too detailed for merging with this one, but it was previously suggested that selected area diffraction be merged with electron microscope, which I think is inappropriate. Let's discuss this further at talk:selected area diffraction. O. Prytz 23:15, 7 October 2006 (UTC)

X-ray focussing limitations??

The statement that, "shorter wavelengths, such as X-rays, exhibit a lack of interaction: both in focussing (nothing interacts strongly enough to act as a lens)" may require revision. This is not my area of specialty, however consider the use of x-ray sources in solution-phase diffraction-based structural determinations (~0.01 angstrom spatial resolution):

        SCIENCE VOL 309 19 AUGUST 2005, pp. 1223-7
        Ultrafast X-ray Diffraction of Transient Molecular Structures in Solution
        H. Ihee, M. Lorenc, T.K. Kim, Q.Y. Kong, M. Cammarata, J.H. Lee, S. Bratos, M. Wulff

We report direct structural evidence of the bridged radical (CH2ICH2I) in a polar solution, obtained using time-resolved liquid-phase x-ray diffraction. This transient intermediate has long been hypothesized to explain stereochemical control in many association and/or dissociation reactions involving haloalkanes. Ultrashort optical pulses were used to dissociate an iodine atom from the haloethane molecule (C2H4I2) dissolved in methanol, and the diffraction of picosecond x-ray pulses from a synchrotron supports the following structural dynamics, with ~0.01 angstrom spatial resolution and ~100 picosecond time resolution... HarriemkaliHarriemkali

I am not an expert, but i believe that exploits periodicity to obtain the improved spatial resolution. Similarly to Bragg diffraction giving plane spaces smaller than the x-ray wavelength, as for interaction synchrotron sources are extremely bright. User A1 13:49, 6 June 2007 (UTC)

Diffraction is not imgaging! Of you can determine the crystal structure using diffraction on a larger single crystal. You see than inverse avarage of the atoms in many, many unit cells, but not the single atom. Sciing (talk) 22:56, 21 January 2017 (UTC)

Picture Label?

I think that image of Staph aureus is an SEM. Yes no?

• The original source of the image states it is a TEM sample produced by freeze drying. 128.243.220.41 14:00, 13 December 2006 (UTC)
• Someone else removed the picture as well. I reverted the change. The micrograph appears to have been published in Guidry et al. Journal of Dairy Science. 74. 3360 (1991). It is also on the web at [1], where it is described as a TEM image. eaolson 04:09, 18 January 2007 (UTC)
  • I emailed the author of that image and he confirmed that it is a TEM image, prepared by shadowcasting a freeze dried sample. Someone has replaced with another TEM image, but I won't revert it since the new one is also a good example TEM micrograph. eaolson 02:36, 19 January 2007 (UTC)

Transmission electron microscopy involves the transmission of electrons THROUGH a specimen to produce an image.

I changed the incorrect introduction to this article. It should not say that a beam of electrons is focused ONTO a specimen causing an enlarged version to appear on a screen or on film. The imaging system, to which the electrons are directed AFTER they are transmitted THROUGH the specimen, is what causes an image. --207.62.177.227 18:10, 9 March 2007 (UTC)

Al-Cu Image

Al-Cu alloy

Hello, i uploaded a BF image of an Al-Cu alloy. Would this be useful in this article? User A1 13:53, 6 June 2007 (UTC)

Magnetic fields

The article stated that magnetic fields are measured in amperes per metre, which is wrong. I'll change it to teslas.

Another thing: this article (as well as the general EM one) has poor punctuation and grammar at times.

Sorry if any of this does not go here.

VonCarrigan 05:28, 27 September 2007 (UTC)

EDITED: Actually, the units might be right (if referring to the H field), but still be wrong if referring to B. If someone else knows better and I was wrong, they can revert it. VonCarrigan 05:49, 27 September 2007 (UTC)

Images

This article, like the SEM article, is in sore need of some good, modern, TEM images of both biological and materials topics. --Blechnic (talk) 06:55, 8 April 2008 (UTC)

There are lots of images on "commons" that we might be able to use [commons http://commons.wikimedia.org/wiki/Special:Search?search=TEM&go=Go] Hat'nCoat (talk) 04:00, 6 September 2008 (UTC)

Short note to image caption of diamond blade image: It gives tiypical section thickness as 70-350nm. In fact, at least the manufacturer whose product is shown, differentiates between ultra knives for sections of 30-70nm, and histo knives, for sections of 50->200 with different edge geometries ("ultra" knives will be damaged by section thicknesses suitable for light microscopy, see below). In fact, standard section thickness for biological samples is 50-70nm for use in TEM. Often, accompanying "semithin" sections of 250-1000nm are cut for orientation in light microscopy.--134.34.122.37 (talk) 16:31, 14 December 2016 (UTC)

Images, diagrams, not micrographs

Can someone flip the filament images? Saw my first (in person) source-on-bottom TEM just this week. Any chance of a field emission filament? --KP Botany (talk) 10:03, 11 April 2009 (UTC)

Flip as in turn upside down? As in with the filament pointing down? If so that is I can do that pretty trivially in inkscape User A1 (talk) 15:25, 11 April 2009 (UTC)

Yes, please, make the filament oriented as it usually is. Thanks. --KP Botany (talk) 20:01, 11 April 2009 (UTC)

History

Very small complaint in that in the first paragraph of the history section, there is no mention of the period of time being discussed- even to the tune of 'in the latter part of the 19th century'. I can't easily find out when it is, but if anyone can add anything to it, it'd be an improvement

Hai2410 (talk) —Preceding undated comment added 13:49, 23 January 2010 (UTC).

I found this linked. I will try to find this. For some reason I missed your comment from my watchlist; sorry about the late reply

User A1 (talk) 20:15, 29 April 2010 (UTC)

This article may to turn featured

Someone might detached this article? Citing references and creating new articles. Sorry, I think that my English is not very good. Did you understand me? Eduardo P (talk) 17:13, 28 November 2010 (UTC)

I think it needs a lot of work before becoming a featured article. It would be a great candidate, though, if the work were done. --Kleopatra (talk) 19:13, 28 November 2010 (UTC)

Three-dimensional imaging

This section has several issues. We should probably link to Electron tomography here, though that page needs a lot of work. The discussion of alignment and reconstruction does not give a full perspective on the breadth of techniques used (e.g. Filtered back projection is not the only reconstruction algorithm), so I am changing the text to correct this. EPadgett (talk) 13:49, 31 July 2015 (UTC)

PerkinElmer TEM photo

I reverted this edit because I didn't see any benefit to the article of adding this picture. There is no information in the caption to help, either. --2601:648:8503:4467:449E:1FBD:9C39:D4AA (talk) 15:13, 3 May 2017 (UTC)

Trying to clean it up from the beginning

I don't know how much time I have, but I'd like to start trying to improve this article starting from the beginning. I'll try to take notes on my rationale for some of the bigger changes.

Deleted reference to "CTEM": Very few people use this abbreviation these days. I don't think it's illuminating to mention it in the first line. CTEM does contrast with STEM, but you can usually do both on the same instrument and there are other techniques like ptychography that blur the lines.

Rewrote parts describing "differential absorption of electrons.": This is a common misconception. Very few electrons are actually absorbed by the sample in TEM. In fact almost none are. I replaced the intro paragraphs talking about this with ones that give a much more nuanced description, emphasizing the wide range of mechanisms and operating modes.

I didn't touch the "history" section because I know relatively little about it.

"Electrons": some very minor edits of things I thought could be misleading. A beam of electrons is like light in some ways but not in others, and I tried to clarify that. It used to say that the velocity "approached" the speed of light, which might suggest that the speed is something like 0.999c, when really 0.5c to 0.8c covers most of the commonly used range.

"Source formation" made no sense to me. I replaced it with "Electron source." This section previously conflated thermionic and field emission sources and also failed to distinguish the cathode, the gun, and the accelerator. It also went directly into the lenses, when this belongs below, in the "Optics" section. I have not yet deleted this paragraph, though, as I'm still rephrasing the information in it in the Optics section. Work in progress...

The "Optics" section itself was focusing very much on the wrong things, especially since there's a more detailed section below on how the lenses themselves work. The reader needs to know why these lenses are there and what they do in terms of system operation.

Running out of time for this session; I feel the "Optics" section is improved but still needs work. I have not started on the later sections yet. Elifint42 (talk) 03:29, 11 March 2019 (UTC)

Erroneous illustration?

Schematic view of imaging and diffraction modes in TEM.

The illustration at right is in the article, but I think it's erroneous. I can't seem to locate the person who made it, so I'm writing this here.

The third lens from the top is at the same level in the two diagrams. In the "Imaging mode" diagram there's text next to it sayin "In image plane of Objective lens", whereas in the "Diffraction mode" diagram the text beside it says "In back focal plane of Objective lens". But they're at the same level. That level cannot be both the image plane and the back focal plane.

It seems to me that in both cases, this lens is too low. In the case of Imaging mode, it should be just a little bit higher, where the three rays on the right or the three rays on the left converge and cross. That's where the image of the specimen will be.

In the case of Diffraction mode, the lens should be even higher up, where the pairs of rays that are parallel above the objective lens cross below the objective lens. There are three such pairs, one pair is going to the left above the objective, one pair is going vertical, and one pair is going to the right. The heights where these pairs cross (under the objective) are all the same. It's like the narrowest point in the "hour glass" shape that we see.

I don't know how we can correct this image, so I guess we have to delete it.

Eric Kvaalen (talk) 17:41, 8 January 2020 (UTC)

Actually, maybe the two labels were supposed to be describing the position of the aperture above the objective lens, not the position of the objective lens. But in that case the labels are misplaced. And the objective aperture in the Imaging mode diagram is shown in the back focal plane, whereas the "selected area aperture" in the Diffraction mode diagram is shown in the image plane! Eric Kvaalen (talk) 08:25, 9 January 2020 (UTC)

Having gotten no feedback, I decided to go ahead and change the diagram. I didn't know how to give it the same name, so I took out a period (full stop). Here it is:

Schematic view of imaging and diffraction modes in TEM.

I have substituted this one into the article. Eric Kvaalen (talk) 11:23, 10 January 2020 (UTC)

Diffraction mode

Now another question: In diffraction mode, shouldn't the electrons hitting the speciment come from a range of directions, rather than being parallel? If they all come from the same direction, then I would think you would get no diffraction spot on the film, or only one if you happen to have the crystal oriented just right. But if the rays are comin from many different directions (a converging cone), then some of them will be hitting the crystal at the right angle to give constructive interference and thus to give a spot on the film (or whatever the detector is). In the diagram it appears, and the article text even says, that "the specimen is illuminated with the parallel beam". Isn't that wrong in the case of diffraction mode? Eric Kvaalen (talk) 11:23, 10 January 2020 (UTC)

Electron gun illustration has incorrect polarity

The electron gun illustration (https://en.wikipedia.org/wiki/File:Electron-gun.svg) has the filament connected to positive side of the "High Tensions", which is incorrect for an electron gun (it should be negative). Then there is also an additional voltage symbol in series with the high tension, also with positive side towards the filament, making the entire illustration confusing. The original French illustration which this is based of, does not mention the polarity of the "High tension" so it is slightly less incorrect in that sense, but it still has incorrect polarity of the voltage symbol. EV1TE (talk) 21:40, 11 February 2021 (UTC)