What is the fermi energy measured relative to?

  • Thread starter Repetit
  • Start date
  • #1
128
1

Main Question or Discussion Point

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
 

Answers and Replies

  • #2
3,763
8
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
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
 
  • #3
78
0
A formal definition of fermi level in SC's is th chemical potential at T=0K.
 
  • #4
can metal be associated with two fermi levels
 
  • #5
Vanadium 50
Staff Emeritus
Science Advisor
Education Advisor
2019 Award
24,017
6,571
This thread is four years old.
 

Related Threads on What is the fermi energy measured relative to?

Replies
2
Views
8K
  • Last Post
Replies
1
Views
2K
Replies
3
Views
2K
Replies
2
Views
1K
Replies
1
Views
995
  • Last Post
Replies
3
Views
5K
  • Last Post
Replies
3
Views
2K
Replies
6
Views
34K
  • Last Post
Replies
19
Views
1K
Replies
0
Views
4K
Top