Semiconductor Energy Gap: Silicon Explained

[alphard]

Hello everyone,

I have a quick question about the energy of the silicon. I know that, as a semiconductor, the silicon has an energy gap between the valence band and the conduction band. But according to this image , http://www.google.fr/imgres?imgurl=http%3A%2F%2Fwww.nano-ou.net%2FImages%2Fsilicon_split.png&imgrefurl=http%3A%2F%2Fwww.nano-ou.net%2FeduNanomaterials2.aspx&h=443&w=665&tbnid=lroOZttxuLz6EM%3A&zoom=1&docid=bVNjJ0Q6l2ncJM&ei=IW8MVYGONYPYOJ-ygeAO&tbm=isch&iact=rc&uact=3&dur=1859&page=1&start=0&ndsp=25&ved=0CCQQrQMwAQ , we see that when the interatomic distance between two atoms of silicon decreases, there is an interval where there is no more "forbidden energy gap" (where the two grey curves are connected). Does that mean that at this point, we have a conductor and not a semiconductor anymore ? I mean, by definition, a semiconductor has an energy gap, not as large as an insulator, but the gap exists. So, without any gap, it should by a conductor.

Thanks for your answers

 

[alphard]

sorry for the image, here is the link:

http://www.google.fr/imgres?imgurl=...dur=29&page=1&start=0&ndsp=25&ved=0CCQQrQMwAQ

 

[arierreF]

Well I am not sure, but there are semiconductors that when are exposed to mechanical strains, or other types of lattice distortions, their band structure changes, and sometimes they transit from semiconductors to conductors. So yes, you can have a material that is a semiconductor in normal conditions and become a conductor under certain conditions.