Timeline for Can the fermi level of a semiconductor be below the valence band?
Current License: CC BY-SA 4.0
12 events
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| Aug 27, 2020 at 11:54 | comment | added | Stian | @ProfM Much like the case for an indirect semiconductor, in some semi metals the bottom of the conduction band can be at a different momentum / wave vector than the top of the valence band. Which then leads to the semimetal properties; asymmetric (anisotropic) conduction of heat or charge, diamagnetic, yet conducting... etc. stuff like that? I might be wrong entirely, but that was why I was (and am) asking tentatively. | |
| Aug 27, 2020 at 10:39 | history | edited | ProfM | CC BY-SA 4.0 |
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| Aug 27, 2020 at 10:34 | comment | added | Camps♦ | The band-gap is defined as the separation between the valence and conduction bands and what define which band is what is the Fermi level. So, in the picture you post, there are gaps between bands (for example in the region 0.5-2eV) but there is no band-gap as the Fermi level is crossing the bands. Band-gap $\neq$ gaps between bands. | |
| Aug 27, 2020 at 10:09 | comment | added | ProfM | @StianYttervik, what property are you referring to? A semimetal like graphene has no band gap but a vanishing DOS at the Fermi energy. The band structure shown above has no band gap at a large DOS at the Fermi level, so I don't think it could be called a semimetal. | |
| Aug 27, 2020 at 9:56 | comment | added | Stian | There are examples of semi metals having this property, no? Graphite for instance? | |
| Aug 26, 2020 at 22:32 | vote | accept | Tristan Maxson | ||
| Aug 26, 2020 at 21:05 | comment | added | Tristan Maxson | That is a good observation. I may update this question someday with an answer if it is that since I will be doing some work on this material potentially. Thanks | |
| Aug 26, 2020 at 20:29 | comment | added | Nike Dattani - No Free Time | +1 for another rapid answer from ProfM! First HNQ in a while :) Keep them coming as it's great for our site! | |
| Aug 26, 2020 at 20:25 | comment | added | ProfM | Looking at NiWO4 in the Materials Project database, the material does have a reasonable band gap: materialsproject.org/materials/mp-25094 However, if you look at the details of the calculations there, they used GGA+U, so my guess is that the calculations that you reported in the post are using an inadequate level of theory. | |
| Aug 26, 2020 at 20:22 | comment | added | Tristan Maxson | Should a metallic material be able to exhibit this sort of "band gap" seen in the band structure though? | |
| Aug 26, 2020 at 20:21 | comment | added | Tristan Maxson | I find this really interesting, NiWO4 is a well known semiconductor material with a quite large band gap (2+ eV). For some reason based on this information, this source is classifying it as a topological insulator which is why I suspected this is the source of weirdness in band structure. | |
| Aug 26, 2020 at 20:10 | history | answered | ProfM | CC BY-SA 4.0 |