Electron Bands Theory (1 Viewer)

[Constip8edSkunk]

This isnt in the syllabus, but out of interest:

In some notes from those hsc enrichment things, the Fermi Level is described as being the top of energy levels at absolute 0 temperature. But in insulators and semiconductors they prostioned in the energy gap between the conducting and valence bands. Why is this the case? wouldnt being teh top of energy levels at absolute zero mean being at the very top of the valence band?

 

[pigs_can_fly]

i have no idea what Fermi levels r, and this is HSC so you should really be concentrating on what is IN the syllabus, but my guess is that in conductors, the valence and conducting bands are the same band, so Fermi Level is above the valence band in all materials. however, in insulators and semiconductors where the two bands are separate, the fermi level is above the valence band, but below the conduction band. don't ask me why/.
also, i could be totally wrong so don't quote me on this either

 

[Constip8edSkunk]

yeah u r right, just argh... i h8 when they give u info and dont explain or relate it 2 nething else....

 

[Dangar]

The Fermi level isn't the top energy levels at absolute zero.

It's the top of the available electron energy levels at low level temperatures. I got that from notes, and now this is my guess why its in the middle:
It is positioned between the conducting band and the valence band for insulators and semi conductors, because at low level temp, a finite number of electrons in the valence band do gain energy but not quite enough to bridge the energy gap, so they end up in the middle. they need either heat or light to make them conduct, hence semiconductors.