I have synthesized bismuth doped titania (Bi-TiO2). Now i am confused about the position of Bismuth. whether it should be above the valence band of TiO2 or below the conduction band of TiO2. Considering the energy level of Bi dopant, please discuss its position with proper reason and references.
Please check the attached image.
The valence of Bi for example can give an idea perhaps, check it with XPS
Dear Noor
To understand the position of Bi in TiO2 you need to first perform Neutron scattering to get a high resolution Data, Next you should perform Rietveld refinement using the TiO2 cif file. However, you will have to perform solid state NMR to understand the coordination number of Bi in the structure.
Using these methods, you will be able to develop a model for your structure which will tell you the exact occupation of your Bi.
There is another method which is called first principle method. in this method you will be able to optimize your geometry based on your primary guess for occupation of Bi. This is an excellent method in which you can even calculate band gap energy using HUMO and LUMO difference and by density of states.
The doping of Bi ions incorporated into the lattice of TiO2 leads to the formation of the intermediate energy levels between the top of the (lone pair) Bi3+ 6 s band and the bottom of the Ti4+ 3d band. It has thoroughly been investigated that level of Bi 6s is located above the valence band of TiO2.
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