I think the following paper will help you:
Metal Oxide Semiconductors-------,Journal of Nanophotonics,vol 1,011660(15 Nov 2007
that's what I got so far:
The absorption of oxygen molecules on metal oxide (ZnO for example) affects the surface states and decreases the conducting channel width. The following equation represents the conductance of ZnO NWs.
G = neµπ[(D − 2W)^2]/4L
where n is the density carriers, D is the diameter of the NW, and W is the width of the surface charge region represented below.
W =Ld (eVs/kT)^(1/2)
where Ld is the Debye length and Vs is band bending induced by the adsorbates. The Debye length is used to scale the depletion region of the NW. At a distance that is equal to several Debye lengths from the surface of the NW, the carriers’ density is equal to the bulk value. Therefore, for large enough NWs (> 2Ld) bulk characteristics are assumed. The following equation is used to evaluate the Debye length.
Ld =[(εk_B T)/(q^2 n)]^½ (5.5)
where ε is the relative dielectric permittivity of the nanostructure and n is the charge-carrier density. It is clear that as the Ld increases with temperature and decays with growing density of donor defects. Usually, the Debye length in ZnO is estimated in the range of few to tens of nanometers.
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