What is the effect of Oxygen vacancies on band structure and band gap of transition metal oxide ( i mean what happen to band gap of metal oxide in more oxygen vacancies introduced?). As known, oxygen vacancies produce mid gap state between conduction and valence band. My question is how this affect the band gap and Fermi level position in case n-type metal oxides or p-type metal oxides. ? Thank you.
Dear colleague Hytham Elbohy,
Have a nice time and good day.
Alsalamo Alicom wa rahmato Allah wa barakatoh.
Herein fined the next suggested articles about the the effect of Oxygen vacancies on band structure and band gap of metal oxide
I wish this is useful and help you.
Yours.
A. El-Denglawey
Thanks Dr. Eldenglawy and Dr. Zakria for your helpful answer. Actually you both right. By increasing the oxygen vacancies in metal oxide, you make it more electrons rich material (basically more n-type) and this would shit Fermi level to be closer to conduction band as well as would shift the Valance band also upward and this why i found that by increasing oxygen vacancies, band gap would change. On the other hand, the electron affinity of the material will also increase because more electrons is added to the metal oxide so we will end up by higher electron affinity after the creation of oxygen vacancies. That is why my questions.
best regards,
Hytham
Hytham,
Hope you are doing well. To add on if you think why certain metal oxides such as TiO2 and ZnO are considered n-type. While the pure form of any material should be intrinsic, these vacancies or interstitial defects actually dope them. While TiO2 can have either Ti interstitial or Oxygen vacancy or both which lead to excess unpaired electron. This can lead to doping of material or in other words make it more n-type. But also remember that these defect states can also take part in charge recombination with active layer itself. Hence most efforts are spent on passivating the surface of metal oxides while bulk defects are less addressed as they aid in charge transport.
Hope this helps.
Just by chance, I seach answer to my question, I found above interesting discussions. May I ask a relavent question, but a new aspect for oxygen vacancy effect which directly affects oxygen ion transport with significant importance in energy applictaions.
How is energy band changes affect ionic transport properties in semiconductors or band structure materials?
In recent years, based on ionic effects on electronic transport phenomena and new emerging electron and semiconductor devices, scientists have proposed “Ionotronics”, but the e-i ( electron-ion) coupled principle applied on ionic transport phenomena, i.e. electron effects on ionic transport in semiconductors or band structure materials has not been fully understood,which may lead to next generation energy conversion technologies and energy devices. Electrolyte (layer) free fuel cell is one of such examples for new energy devices.· 1. Zhu, B., Raza, R., Abbas, G. and Singh, M., An Electrolyte-Free Fuel Cell Constructed from One Homogenous Layer with Mixed Conductivity, Adv. Funct. Mater. 21 (2011)2465-2469.· This work is reviewed and highlighted in Nature Nanotechnol.:· Nature Nanotechnology | Research Highlights: "Three in One", Nature Nanotechnology, Volume: 6, Page: 330 (2011). doi:10.1038/nnano.2011.89· 2. Zhu, B., Raza, R., Qin, H., Liu, Q. and Fan, L., Fuel cells based on…
It was very intersing discussion but I have a new problem. In my case I got more n- type nature of TiO2 with increasing Mn -ion concentration(as a doping agent) and also found decreasing oxygen vacancies concentration. What should be the proper reason ? @ Jafar Hussain Shah , Bin Zhu , Hytham Elbohy , M. Zakria , A. El-Denglawey
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