Electron-acceptor Strength is derived from Zhang ionocovalency

Yonghe Zhang ionocovalent theory applications (14)

Yonghe Zhang

American Huilin Institute, http://www.amhuilin.com/

 

      Hoffman and al. [64, 65] have shown that, for sputtered highly degenerated ITO (indium tin oxide) films (n > 1020 cm-3), the conduction-band electrons are strongly scattered at the ionized donor centers. However, Wen et al. [66] proposed that “such a scattering effect (which, obviously,also inhibits the carrier nobility) should, a priori, be partially weakened if more appropriate n-type dopants are used to partially or totally substitute for tin in ITO. In fact these dopants M (m-n)+ should, ideally, be such as the ground energy states associated with the oxidized donor centers Mm+  gives:

 

M (m-n)+  ____> Mm+   + ne- [C.B.]

 

Where e- [C.B.] symbolizes the conduction-band electrons and are located in the conduction band in order to minimize their interaction with the carriers.

On the other hand, a valuation of the “electron-acceptor strength” (EAS) of the ionized doping elements, Mm+can be carried out using the empirical relationship established by Zhang [17]:

 

L = z/rk2 – 7.7X + 8.0

 

where L symbolizes the “Lewis acid strength” of the element. z/rk2 (where z is the charge number of the atomic core and rk2 is the ionic radius) is related to electrostatic force and Xz symbolizes the electronegativity of elements in valence states.”

They have reported [67] that the “electron-acceptor strength” of the ionized donor centers, Mm+, decreases as the “Lewis acid strength”, L, of the element increases. Consequently, high mobilities, and thereby high conductivities, are likely to occur for ITO (or IO) samples heavily doped with donor centers having high L values, particularly in their oxidized form.

 

[17] Y. Zhang,, Inorg Chem., 1982, 21, 3889.

[64] H. Hoffmann, J. Pickl, M. Schmidt, and D. Krause,  Appl. Phys. 1978, 16, 239.

[65] H. Hoffmann, A. Dietrich, J. Pickl, and D. Krause Appl. Phys. 1978, 16, 381

[66] S. J. Wen, G. Campet, and J. P. Manaud Active and Elec.Comp.,1993,Vol.15,pp.67-74

[67] S. J. Wen, G. Campet, J. Portier and J. Goodenough Mat. Science and Eng.,B (accepted 1992)

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