The Naked Scientists

The Naked Scientists Forum

Author Topic: How do they know the tip of a scanning tunneling microscope is 1 atom thick?  (Read 1525 times)

Offline chris

  • Neilep Level Member
  • ******
  • Posts: 5336
  • Thanked: 65 times
  • The Naked Scientist
    • View Profile
    • The Naked Scientists
An electron microscope has a very fine tip; we're told it's a single atom at the end. How do they a) make that and b) know that they've achieved it?


 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8659
  • Thanked: 42 times
    • View Profile
The tip is, pretty much by definition, the end of the needle. There has to be an atom there, so the tip is an atom.
I know they used to make them by electrolytically etching tungsten wire, but they may have other technique too.
 

Offline evan_au

  • Neilep Level Member
  • ******
  • Posts: 4113
  • Thanked: 245 times
    • View Profile
If the tip of your needle was a hemisphere of 0.5mm diameter, you would not be able to pick up the patterns of metal on a semiconductor chip, let alone the surface undulations of individual silicon or aluminium atoms on that chip.

If you make the needle from wire which is very fine, you can be sure the tip is not 0.5mm in diameter. So the construction method is important. But then you can test it.
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8659
  • Thanked: 42 times
    • View Profile
 

Offline chris

  • Neilep Level Member
  • ******
  • Posts: 5336
  • Thanked: 65 times
  • The Naked Scientist
    • View Profile
    • The Naked Scientists
 

The Naked Scientists Forum


 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums