How a Scanning Electron Microscope Works.wmv

The basics of how a scanning electron microscope works.

[enderuslu]

This is the best practical SEM lecture I have ever seen!.

[manasikashyap]

Thank you. This is the best & easiest to understand explanation so far. So clear & simplified.

[PricelessBeauty]

Thank you so much for this video! You definitely saved me for this part of my nanotechnology quiz tomorrow!

[murrygans]

Sorry for taking so long to get back to you.  We were on break and the book I needed was in my office at the college.

This is a weird one, so I went back to my textbook for an explanation.  Yes, the anode is negatively charged, but relative to the filament on the scope it is positive.  Here is a quote from the text:

 "If one induces the emission of electrons from a filament as described above, this will result in the emanation of electrons in all directions.  Without a mechanism for guiding them, most of the electrons would not enter the illumination system.  A second part of the electron gun, the shield (also called Wehnelt cylinder, bias shield, or grid cap), is a caplike  structure that covers the filament and is maintained at a slightly more negative voltage potential than the filament.  Because it is several hundred more negative than the 50 to 100 kV electrons, the shield surrounds the electrons with a repulsive field that is breachable only through a 2 to 3 mm aperture directly in front of the filament tip.  Electrons exit the shield aperture and and are drawn toward the apertured disc, or anode, the third part of the electron gun.  The anode is connected to ground so that the highly negative electrons are are strongly attracted to it.  THUS IT IS POSITIVE WITH RESPECT TO THE GUN.  In fact, the highly attractive pull of the anode in combination with the negative surface of the shield act as an electrostatic "lens" to generate a crossover image of the electron source near the anode."

Bozzola, John J., and Lonnie D. Russell. Electron Microscopy. 2nd ed. Sudbury: Jones and Bartlett, 1999. Print. 0-7637-0192-5

I could not agree with you more - it seems backwards.  The anode is negative, but it is positive related to the beam.

Let me know what you think.  There is also an illustration in the text I would be glad to photograph and send to you if you provide me an e-mail or text address.

Many thanks for your comment.

Murry

[fa]

Thanks for this explanation Mr. Gans! Due to my SEM presentation for exam, I'd like to use your video and put your name as courtesy.

[vxecho]

doing forensics at the moment and was giving myself a headache trying to understand the different forms of electrons & how they actually worked - this cleared up almost everything! thanks for uploading :)

[PathToEntrepreneurship]

Thanks for the video! I am taking a university course in engineering on materials science and we had to explain in lab report how this device worked. With your great explanation I can understand much better.

[yefengli]

very good science video. really help understand how does a SEM work. highly recommended

[rodbaird]

Murry, you are the Man.  Great video!

[farshinanazrul]

best best best video explaining the working principle ^_^ thank you so much

[murrygans]

I appreciate your comment and I agree that this is not a research-level explanation - it was not intended to be. I demonstrate a Hitachi TM1000 to elementary, middle, and high school students. This is one of the videos I forward to the teachers ahead of time to prepare their classes. I also use it as a basic introduction to electron microscope for some of the students I teach at a community college - many of whom are not science majors. But I do appreciate your comment.

[jiejiang]

sir, why the secondary electron are from the surface of sample, and the X-ray are from the deeper within the specimen? Thank you .

[drabhijit]

You should have talked about the raster scanning meathod. you should have also explained about the EDAX spectrum and explained the way to read/uncode the EDAX spectrum. over all its a good video. it has explained all the basic points but not that good for a research level thing. I hope you include the above mentioned things and make an other video.

[patriciagilderubio]

So the back scattered electrons are the electrons given off by the atoms of the specimen that are located deeper within?

[sumyunguy]

My understanding is that there needs to be a vaccume inside the microscope, that way electrons aren’t going to come into contact with anything other than the target specimen.

My question is, how does a specimen stay where they need it to? Glass slides would get in the way of the electrons and a vaccume would move the specimen...wouldn’t it?🤔

[swatisingh]

Sir, why we coat the sample with gold?

[georgem]

How can SEM be used to image higher resolution than light microscopes, and how is this different for typical thermionic and field emission electron source microscopes.

[guangyuren]

very useful, thank you. however, it is weird to scan a Cockroach with

[austiblazeit]

I’m not from your college, I’m still in high school actually, but an amazing video to watch nevertheless

[anasomar]

what is the possibility of bias for a 5 nano meter specimen ?