Hello scientific community,
I have a question about the gas sensing mechanism by n and p-type metal oxide semiconductors. It is well known that the gas sensing mechanism is in most cases related to the effect of adsorbed oxygen. let us take the cas eof an n-type semiconductor. when the oxygen species adsorbate on the surface, they will trap electrons from the inner of the film. thereafter, when the sensor is exposed to a reducing gas, the electrons trapped by the adsorbed oxygen will return to the film. now, what's going to happen if the sensor intracts with an oxidizing gas ?
Thank you a lot for your help,
Mr. A. CHETOUI
see the following article
S.Roy Morrison, Sensors and Actuators 11 (1987) 283.
Dear Kompitsas,
very interesting paper. thank you a lot for your help.
Best regards,
A. CHETOUI
Hello,
You may also have a look into my personal web site: www.laser-applications.eu.
We have done a lot of work developing new materials for gas sensing applications.
See our published articles.
Best regards,
MK
Oxidizing gases in the case of n-type MOXs acts as acceptors that increase the resistance of the film and the reverse is for p-type MOXs.
here is an article that may help.
generally,
for n-type semiconductors (eg ZnO) a reducing gas like H2 increases its conductivity, an oxidizing gas (eg NOx) decreases its conductivity.
For p-type semiconductors (NiO, CuO etc) the response is exactly the opposite.
MK
Dear Kompistas,
your explanation is completly wright but it's only understandable if we consider the interaction of the gaseous species with the gas sensor surface. I would like to know if the gas interacts with the preadsorbed oxygen. i've found in an article that the interaction of a reducing gas with the preadsorbed oxygen on a p-type semiconductor conducts to release electrons to the material. the question is: what are the chemical mechanisms or reactions which are managing the interaction of a gas (reducing and oxidizing) with the preadsorbed oxygen for a p-type semiconductor. same thing for the n-type.
Best regards,
A. CHETOUI
Dear Abdelmounaim Chetoui,
if one takes typical oxidizing gases like NO2 or O3 two general interactions can be assumed to happen:
(i) An interaction solely based on adsorption and desorption, i.e. no decomposition of the gas. In case of NO2 the ionosorption of NO2 as (NO2)-ads is proposed:
NO2,gas + e- --> NO2-ads
(ii) The dissociation of the oxidizing gas forming an ionosorbed oxygen species, ie.e healing an oxygen vacancy:
2 NO2 + 2VO + 4e- --> N2 + O2 + 2 O2-
Both mechanisms are hypothetical and may depend on the material itself and the operation temperature. In general for oxidizing gases the number of (operando) spectroscopic works is quite small.
With kind regards,
David Degler
dear Degler,
thank you for your contribution but this is not really what i'm looking for.
Best regards,
A. CHETOUI
Dear Abdelmounaim Chetoui,
if you are generally interested into (possible) "mechanisms or reactions which are managing the interaction of a gas (reducing and oxidizing) with the preadsorbed oxygen" for n- and p-type semiconducting metal oxides you should have a look on the following works:
- D. Kohl, J. Phys. D. Appl. Phys., 2001, 34, R125–R149.
- D. Kohl, Sensors and Actuators, 1989, 18, 71–113.
- W. Göpel and K.-D. Schierbaum, Sensors Actuators B Chem., 1995, 1–12.
- D. Degler, et al., J. Phys. Chem. C, 2015, 119, 11792–11799.
- J.-M. Ducéré, et al., J. Comput. Chem., 2012, 33, 247–58.
- N. Barsan and U. Weimar, J. Electroceramics, 2001, 7, 143–167.
- N. Barsan et al., J. Electroceramics, 2010, 25, 11–19.
I hope these works could help to answer your questions.
With kind regards,
David Degler
dear Degler,
could you send me this article, it's urgent, please.
G. Heiland, H. Lüth, Adsorption on oxides, in The Chemical Physics of Solid Surfaces and Heterogeneous Catalysis, vol. 3B, Elsevier, Amesterdam, 1983.
Sorry, I thinkt it is a book chapter and I don't have access to this book.
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