Fermi level

[logearav]

Revered Members,

Can i know what is meant by fermi level? I googled this, but i could not understand. One site says Fermi level as top of collection of electron energy levels at absolute zero. As far as my knowledge I know electron energy levels as K, L,M, N etc with energy values -13.6eV, -3.4eV etc. Top of collection means, is it O eV?

[swansont]

Revered Members,

Can i know what is meant by fermi level? I googled this, but i could not understand. One site says Fermi level as top of collection of electron energy levels at absolute zero. As far as my knowledge I know electron energy levels as K, L,M, N etc with energy values -13.6eV, -3.4eV etc. Top of collection means, is it O eV?

 

It's for solid-state systems. It's the level when all electrons are in their lowest state — no thermal excitation at all. The Fermi level is the top of the electron level in the highest occupied band.

[logearav]

Sir, I can't understand. Could you elaborate, please?

[swansont]

http://hyperphysics.phy-astr.gsu.edu/hbase/solids/fermi.html

http://www.chembio.uoguelph.ca/educmat/chm729/band/fl.htm

[logearav]

The Fermi Level is defined as the highest occupied molecular orbital in the valence band at 0 K, so that there are many states available to accept electrons, if the case were a metal.

Thanks swansont. Fermi Level is the highest occupied molecular orbital. I can't understand " so that there are many states available to accept electrons". Let me have a try. If fermi level is occupied , then how it is possible to say many states are available to accept electrons, because fermi level is the highest level and also occupied so no state can exist above fermi level. Sorry for stretching you, i am a novice. Thats why i ask for explanation.

[swansont]

The Fermi Level is defined as the highest occupied molecular orbital in the valence band at 0 K, so that there are many states available to accept electrons, if the case were a metal.

Thanks swansont. Fermi Level is the highest occupied molecular orbital. I can't understand " so that there are many states available to accept electrons". Let me have a try. If fermi level is occupied , then how it is possible to say many states are available to accept electrons, because fermi level is the highest level and also occupied so no state can exist above fermi level. Sorry for stretching you, i am a novice. Thats why i ask for explanation.

 

There are an infinite number of states an electron could occupy. The Fermi level represents the highest level that they do occupy (at 0 K), like the surface of water in a cup. But the cup isn't full — there are available states above that surface. If you excite electrons, they will go to the higher states.

 

Solid-state physics is not novice-level material. It might be best if you spent some time studying the underlying physics. That will make it easier to understand the more advanced concepts. because my first reaction to a question on the Fermi level is that you understand the basics about band structure and how that comes about from atomic structure. Since you aren't asking about those concepts, I assume you understand them. If that's not the case, you have to go back and get a handle on them.

[logearav]

Thanks a lot swansont. Now i understood by your analogy with water in a cup. Thanks a ton. Now i could grasp. People like you is an asset for this forum.