Dear Scholars
I would like to ask about the effect of doping (anatase TiO2 ) with a strange transition metal (Mn or Fe) what is the mechanism that this strange element do to reduce the band gap of the anatase TiO2 because I read some papers but still do not get it. I know that the transition metal oxide sometimes has lower band gap than TiO2 but how can this transition metal contribute to narrow the band gap of the main semiconductor?
Regards,
Hello, Sometime the type of metal or the amount of it are depressed the Bg that depended on method of doped the transition metals on TiO2. In general, the crystal size of TiO2 between 1-10 nm or 10-100 nm is affected on the value the bg after doped.
Regards
By doping with a metal, one introduces additional CB levels within previous BG of the TiO2 thus lowering the BG value.
I would recommend reading the info at the address:
http://collaborations.fz-juelich.de/ikp/cgswhp/cgswhp12/program/files_batumi/14-08-2012/Parallel_Session_5/1_Kazimierz.Conder_Batumi.pdf
additinally, please be awear that if enough iron is the "dopant" than you might get a diode type behaviour (n-TiO2 and p_FeO) and thus a different activation reason.
I am agree to Kirill answer which is the exact and to.the point.
Doping of TiO2 has been proved as a significant way in band gap engineering in order to change the optical properties of semiconductor photocatalysts. The insertion of a metal ions dopant in the TiO2 lattice may affect the band edge positions or introduce impurity energy level or defects or additional energy levels in the band gap of the photocatalyst. Electron transfer from these levels to the conduction band (CB) of semiconductor needs lower photon energy as compared to an unmodified or pure semiconductor. However, the impurity energy levels formed can also act as recombination centre for the photoexcited electrons and holes in the case of doping at a high concentration.
As a model of material in your case where normally one adds an appreciable doping to the native oxide some form of two compounds mixed with each other results or a ternary compound. Accordingly the new material after doping will be a mixer of MnO and TiO2. There is a rule of thumb for new composite bandgap. It will be the weighted average of the bandgaps of the constituting compounds.
So, if MnO has lower band gap than TiO2 , the resulting ternary compound will have basically a lower bandgap than the binary compound TiO2.
Really MnO has lower band gap than TiO2.
Best wishes
Dear Kirill Sliozberg
Thanks for your wise comment. Would you please tell us what will happen if the band gap of dope materials are lower or higher that TiO2.
@ Kirill Sliozberg
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