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Effect of trivalent dopants on local coordination and electronic structure in crystalline and amorphous ZnO


Type

Article

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Authors

Muñoz Ramo, D 
Chroneos, A 
Rushton, MJD 
Bristowe, PD 

Abstract

Density functional theory calculations are used to investigate the structure and binding energies of clusters formed between oxygen vacancies and trivalent dopant atoms (indium, gallium and aluminium) substituted into zinc oxide. Our results show that indium atoms form stable nearest neighbour pairs with oxygen vacancies, while gallium and aluminium atoms associate with them at next nearest neighbour sites. Using a combination of classical molecular dynamics and Reverse Monte Carlo methods, models of amorphous indium zinc oxide at different compositions up to 25 at.% indium are created. Analysis of these models indicates that, in contrast with the trend observed in the crystal phase, indium does not tend to be undercoordinated in the amorphous phase. The value of the band gap obtained for the amorphous compositions is smaller than that of crystalline undoped ZnO by about 0.8 eV and is largely independent of the indium concentration. Electron effective masses calculated in all the amorphous models decrease with increasing amount of indium due to the larger dispersion of the In-dominated conduction bands. This trend is compared to resistivity measurements on amorphous indium zinc oxide which also decrease with increasing indium concentration.

Description

Keywords

ZnO, In:ZnO, Amorphous ZnO, DFT, Molecular dynamics, Reverse Monte Carlo, Defect states, Pair distribution function

Journal Title

Thin Solid Films

Conference Name

Journal ISSN

0040-6090

Volume Title

555

Publisher

Elsevier
Sponsorship
Financial support for this work is provided by the European Commission through contract No. NMP3-LA-2010-246334 (ORAMA).