Ionocovalency Predict the Approaches to Improving BZO Film

Yonghe Zhang ioniccovalent theory applications (30)

Yonghe Zhang

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

 

On the basis of Zhang’s ionic-covalent theory and approaches of electronegativity, Lewis acid strengths and polarizing power, multilayer transparent conducting boron-doped zinc oxide films have been prepared on glass substrates by the sol gel dip coating process by Bel Hadjtahars [64]: “Of special note are the relatively large carrier densities (almost double) measured for AZO films compared to those observed for BZO coatings that were prepared at the same conditions including the dopant level, Table II. The difference in the doping performance may be analyzed on the basis of the electronegativities and the Lewis acid strengths of the cations.  Zhang1982established the following relation that relates the Lewis acid strength “Lz” of a cation to its electronegativity “Xz”and Z/rk2:

Lz = – 7.7 Xz + 8.0

Where rk is the empirical ionic radius and Z is the charge number of the atomic core. The values of Lz, Xz, and Z/rk2 for B3+, Al3+, and Zn2+  are shown in Table I.

 

Table1 Atomic Parameters

 

Cationic radius

Polarizing

Electronegativity

Lewis acid strengths Lz

Elecment

rk (A)

power Z/rk2

Xz

Boron

0.23(B3+)

17.85

1.97

10.7(B3+)

Aluminum

0.56(Al3+)

6.58

1.49

3.04(Al3+)

Zinc

0.74(Zn2+)

3.66

1.43

0.66(Zn2+)

 

A remarkably high Lz and Xz values are observed in the case of boron indicating that this atom is relatively more tightly bonded to oxygen. Thus, relatively more oxygen is expected to remain in the BZO thin film even after annealing. The excess oxygen atoms neutralize the dopants and provide additional neutral scattering centers and, therefore, limiting the carrier density and nobility. ...Thus, future research in the field of transparent conductors should focus on minimizing the density of neutral compounds by optimizing the parameters involved in the post-deposition annealing. In this respect, lower oxygen pressure may help in the donor regeneration.” 

[16] Y. Zhang,, Inorg Chem., 1982, 21, 3886.

     Y. Zhang,,"Zhang Electronegativity" in "Introduction to Modern Inorganic Chemistry" ( Eds: K. M. Mackay, R. A. Mackay, W.Henderson, ) 6th ed., Nelson Thornes, United Kingdom,2002, pp 53-54).

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

[64] R. B. Hadjtahar and N. B. Hadjtahar, Journal of Materials Science, 2005, 40, 5285.

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