What is the fermi energy measured relative to?

[Repetit]

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

 

[marlon]

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

 

[armandowww]

A formal definition of fermi level in SC's is th chemical potential at T=0K.

 

[abdulhakim]

can metal be associated with two fermi levels

 

[Vanadium 50]

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