Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is the fermi energy measured relative to?

  1. Mar 18, 2007 #1
    Hey!

    When we say that the fermi energy of a certain metal is for example 2 eV what are the 2 eV measure relative to? The top of the valence band? If so, wouldn't the fermi energy of a semiconductor at 0 K be 0 eV?

    Thanks
     
  2. jcsd
  3. Mar 19, 2007 #2
    In the case of a metal, the WF is expressed with respect to the vacuum level : "the work function it the energy needed to bring an electron from the fermi level to the vacuum level AND KEEP IT THERE"

    What i mean with the addendum "KEEP IT THERE" is that once you bring an electron "outside" a material into the vacuum, there is going to be an image potential that wants to pull back the electron towards the material's surface. So a WF must also include this : not only is it the energy to get an electron outside the metal (ie get it out of the conduction band in the case of metals for example) and to [ii] put the electron into the vacuum (ie overcome the surface potential) but also to [iii] keep the electron at the vacuum level (ie overcome the image potentials).

    In the case of SC's, the fermi level does not really exist. I mean, fermi level is defined for metals. In the SC case, the proper term is chemical potential.

    marlon
     
  4. Apr 25, 2007 #3
    A formal definition of fermi level in SC's is th chemical potential at T=0K.
     
  5. Sep 29, 2011 #4
    can metal be associated with two fermi levels
     
  6. Sep 29, 2011 #5

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2015 Award

    This thread is four years old.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: What is the fermi energy measured relative to?
  1. Fermi energy in 2d (Replies: 3)

  2. Fermi energy (Replies: 3)

  3. Fermi energy (Replies: 3)

Loading...