Scanning electron microscope

  • Thread starter Will
  • Start date
  • #1
Will
I know that optical devices are limited in the detail that can be seen because of the size of the wavelength of visible light. What is the limit, the smallest thing that can be seen with an optical device? Is the level of detail directly proportional to the wavelength? So what is the wavelength used by the SEM? Is this the device that can show the highest detail?
 

Answers and Replies

  • #2
BoulderHead
Hello Will,

I posted this once upon a time back in PF2. So far as I know this was/is the most powerful optical microscope ever built (The Universal Microscope);

http://www.rife.de/mscope/mscope1.htm
 
Last edited by a moderator:
  • #3
Alexander
So, what is the resolution of this microscope? Wavelength? Half wavelength? Quater?
 
  • #4
418
3
SEM

SEM's today use electrons with anywhere from 2 - 50 KeV of energy and you can get ~5 nm resolution, or better, with them quite easily. The highest resolution devices are scanning transmission microscopes.

JMD
 
  • #5
Alexander
Is Rife microscope a SEM?
 
  • #6
BoulderHead
Originally posted by Alexander
Is Rife microscope a SEM?
Alexander,
Have you clicked on the link I provided?
 
  • #7
Alexander
Yes. It does not say what is the resolution of Rife microscope (say, 0.1 micron for blue light, or half wavelength for visible, or anything like this).

So, the question - what is best resolution of optical microscope achieved so far - is still open.
 
  • #8
BoulderHead
In the 1870s, a man named Ernst Abbe explained why the resolution of a microscope is limited. He said that since the microscope uses visible light and visible light has a set range of wavelengths. The microscope can't produce the image of an object that is smaller than the length of the light wave.

More details here;
http://hypertextbook.com/facts/1999/GeetikaKumar.shtml
 
  • #9
FZ+
1,561
3
Basically, as light waves hit really small objects, they experience diffraction, and also interference. This limits the resolution you get from it. You can decrease the wavelength of you em waves to get better resolution, but then you have another problem - you have weak signal intensity because then the waves tend to go THROUGH the object, or THROUGH the receiver.
By using electrons, you can get better resolution because the debroglie wavelength of electrons are much smaller than the wavelength of standard em radiation. Hence, you experience less diffraction, less interference and hence better quality.
 
  • #10
eNtRopY
On a good day, the SEM in our lab can resolve 10 nm. Of course, we can use it to write lines typically ~40 nm thick on a PMMA surface.

eNtRopY
 
  • #11
Alexander
What is PMMA? Do you write lines to make a mask for photolithography?
 
  • #12
418
3
PMMA is polymethyl methacrylate, it's an organic resist. When PMMA is exposed to electrons, bonds between molecules is broken. So the exposed areas have a lower molcular weigth than the unexposed areas. You then use MIBK(Methyl Isobutyl Ketone) and IPA to devlop, or remove the exposed areas of PMMA. Then you can evaporate metal unto the wafer, then remove rest of the PMMA, leaving only the pattern you exposed made with a thin layer of metal.
 
  • #13
Alexander
Cool. How do you remove PMMA from under metal (gold, I presume)?
 
  • #14
418
3
IPA breaks it down and removes it. Acetone also works, but not as well.

JMD
 

Related Threads on Scanning electron microscope

  • Last Post
Replies
2
Views
2K
Replies
3
Views
1K
  • Last Post
Replies
15
Views
9K
Replies
8
Views
2K
Replies
4
Views
3K
Replies
12
Views
2K
Replies
18
Views
907
Replies
3
Views
1K
Replies
9
Views
11K
Replies
23
Views
592
Top