Codoping Method

Although nitrogen has been considered as the best candidate for p-type doping for ZnO, the point should be remade that the solubility of N in ZnO is low and it introduces a relatively deep acceptor level. Therefore, it is necessary to find methods that can enhance the solubility of N in ZnO and lower the acceptor ionization energy. 

For this purpose, a donor-acceptor codoping method has been proposed to realize highly conducting p-type ZnO [65,134,135] and the experimental studies based on this approach have been performed [66, 136-140]. 

Ohshima et al. [138] have attempted to synthesize p-type ZnO by PLD using various codoping methods, including the ablation of ZnO Ga target in NO gas and Al and N codoping using an ion gun and a microwave electron cyclotron resonance source. Although they could identify the presence of Ga-N bonds in ZnO, p-type ZnO film could not obtained. 

A1 + N codoping has been undertaken during the growth of ZnO films in an N2O + O2 atmosphere on glass substrates by DC reactive magnetron sputtering. At a substrate temperature of 500 °C, p-ZnO was realized with hole densities as high as 1.1 X 10 cm  

In other codoping experiments [66,137,140], however, no p-type conductivity was observed even though N concentrations as high as 2 x 10 cm were noted in ZnO. However, such codoped ZnO layers in these experiments exhibited a dramatic increase (by eight to nine orders of magnitude) in resistivity. The formation of N-Ga-N acceptor centers in the samples was suggested to be the reason. 

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A 8. 6 Theory of codoping of acceptors and reactive donors in GaN E CODOPING METHODS... 

Again, despite reports of successful p-type ZnO and even reports of p-n junctions (see Refs [147, 148]), whether using codoping methods or otherwise, the choice of dopant and the method to be employed are controversial and the rehabUity and reproducibility of p-ZnO are open for debate. 

Yamamoto, T. and Katayama-Yoshida, H. (1999) Solution using a codoping method to unipolarily for the fabrication of p-type ZnO. Japanese Journal of Applied Physics, Part 2 Letters, 38, L166. 

Shi et al. prepared CeF3 Lu " NPs from the quaternary reverse micelle system, which contained CTAB, n-butanol, -octane, and water. The characteristics emission of Lu + was observed (Lian et al., 2004). Similarly, Qin et al. obtained Yb -Tm + codoped YF3 nanobundles through a microemulsion method in another quaternary reverse microemulsion system with water/CTAB/cyclohexane/l-pentanol (Wang et al., 2008c). 

Codoping is sometimes a suitable method to get visible tight response. For example, Ti02 codoped Sb with Cr is active for O2 evolution whereas only Cr-doped Ti02 is inactive as usual [17]. The codoping contributes to the compensation of the charge and distortion resulting in the suppression of recombination centers. 

D. Huang, S. Liao, J. Liu, Z. Dang, L. Petrik, Preparation of visible-light responsive N-F-codoped Ti02 photocatalyst by a sol-gel-solvothermal method . Journal of Photochemistry and Photobiology A Chemistry, 184, 282-288, (2006). 

Wang NL, Zhang XY, Jiang HT, Dong TT, Yang D (2012) Fabrication of Er AT> codoped Y2O3 transparent ceramics by solid-state reaction method and its up-conversion luminescence. Mater Chem Phys 135 709-713... 

An electrohydrodynamic pol5mierization technique was introduced for the electros5mthesis of CP/insulating pol3mier nanocomposites. By this method optical active PANl colloids were prepared in a divided electrochemical flow-through cell via the polymerization of aniline in aqueous sulfuric acid/enantiomer of 10-camphorsulfon-ic acid, and polystyrenesulfonic acid as a stabilizer and codopant ... 

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