Thickness Effect and Mesoscopic Character of the Metal Oxide Gas Sensing Nano-Thin Films


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The characters of metal oxide gas sensing nano-thin films are studied. The formula of the dynamical thickness effect characteristic time is given. The relation of the sensitivity Sn and the film thickness l, the character of existing the optimum thickness, the character of the change of conductance activity energy with the film thickness are given also. The idea of diffusion reaction of gas sensing mechanism and the idea of mesoscopic effect in the nano-thin films are proposed.



Solid State Phenomena (Volumes 121-123)

Edited by:

Chunli BAI, Sishen XIE, Xing ZHU




J. P. Xing et al., "Thickness Effect and Mesoscopic Character of the Metal Oxide Gas Sensing Nano-Thin Films", Solid State Phenomena, Vols. 121-123, pp. 1341-1346, 2007

Online since:

March 2007




[6] . Because the works are of great value to both academic and technical, a lot of scientists are in pursuit of it in the 1990's.

[4] , 7~14] . But the theoretical result are: the sensitivity is as higher as the size of crystal grains being smaller, Sn→ ∞ when r0 is near to zero. However, our experiment shows that there is optimum size r0 * of crystal in metal oxide semiconductor gas sensing materials. The research of nanometer solid materials in the last of1980's, which was regarded as the fundamental research in physics field, spreads to the fields of metal-oxide semiconductor gas sensing materials in the 1990's.

[15] , 16] . It's ambiguity about the basis of experiment and theory why to use the nanometer solid gas sensing materials. As a result of our experiment and theory calculation, it shows that: the optimum crystal size of n-type metal-oxide semiconductor gas sensing material is about 10 0 nm. Why Sn(r0→0)→∞, when using macroscopic theory analysis, with no existence of optimum sensitivity * 0r ? The key reason is that macroscope Fermi statistics is used to deal with the electron distribution under the mesoscopic size r0=100 nm and on the surface of crystal grains. The key question is correcting the Fermi statistics formula of ns in order to adapt ns→0. In another word, the gas sensing crystal can keep electric neutrality when the size of gas sensing r0→rm.


[17] , 18] We will discuss the above opinion in other articles. Acknowledgement We would like to acknowledgement support from the National Natural Science Foundation (NSF) Grant No. 60372030. Reference.

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