I am working on the electronic band structure of some topological insulators. When I doped some impurity into it, the valence band of it moved downward away from the Fermi level while the conduction band approached to the Fermi level. What can we expect/explain from this??
Band shifts by stoichiometry changes are usually exactly the thing you want to achieve with it, probably at some point you will need to reclassify your topological insulator as "sufficiently doped to count as a semiconductor". What can we expect from this? If you bring this material in contact with other materials, the bands will bend differently:
https://en.wikipedia.org/wiki/Band_bending
So, whatever conductivity change you want to introduce, you can tune it by the dopant/additive concentration.
Band bending is a very common phenomena that exists in semiconductors. Upon doping insulator or semiconductors with foreign elements lead to the shift in the CB/VB edge positions. So basically u can tune their positions as per your requirement for the desired application. Since ur CB is coming down probably u have introduced sufficient amount of dopant and hence ur material may now have some conductivity (semiconductor). There are many literature reports available on this concept.
The impurities that are added to the base material in a certain proportion improve the conductivity of the base material. The impurities are used to obtain the required conductive semiconductor material, as the value of the energy gap can be controlled.
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