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Recrystallization of highly-mismatched BexZn1–xO alloys : formation of a degenerate interface
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Park, Dae-Sung, Vasheghani Farahani, Sepehr, Walker, Marc, Mudd, James J., Wang, Haiyua, Krupski, Aleksander, Thorsteinsson, Einar B., Seghier, Djelloul, Choi, Chel-Jong, Youn, Chang-Ju and McConville, C. F. (2014) Recrystallization of highly-mismatched BexZn1–xO alloys : formation of a degenerate interface. ACS Applied Materials & Interfaces, Volume 6 (Number 21). pp. 18758-18768. doi:10.1021/am5043388 ISSN 1944-8244.
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Official URL: http://dx.doi.org/10.1021/am5043388
Abstract
We investigate the effect of thermally induced phase transformations on a metastable oxide alloy film, a multiphase BexZn1–xO (BZO), grown on Al2O3(0001) substrate for annealing temperatures in the range of 600–950 °C. A pronounced structural transition is shown together with strain relaxation and atomic redistribution in the annealed films. Increasing annealing temperature initiates out-diffusion and segregation of Be and subsequent nucleation of nanoparticles at the surface, corresponding to a monotonic decrease in the lattice phonon energies and band gap energy of the films. Infrared reflectance simulations identify a highly conductive ZnO interface layer (thicknesses in the range of ≈10–29 nm for annealing temperatures ≥800 °C). The highly degenerate interface layers with temperature-independent carrier concentration and mobility significantly influence the electronic and optical properties of the BZO films. A parallel conduction model is employed to determine the carrier concentration and conductivity of the bulk and interface regions. The density-of-states-averaged effective mass of the conduction electrons for the interfaces is calculated to be in the range of 0.31m0 and 0.67m0. A conductivity as high as 1.4 × 103 S·cm–1 is attained, corresponding to the carrier concentration nInt = 2.16 × 1020 cm–3 at the interface layers, and comparable to the highest conductivities achieved in highly doped ZnO. The origin of such a nanoscale degenerate interface layer is attributed to the counter-diffusion of Be and Zn, rendering a high accumulation of Zn interstitials and a giant reduction of charge-compensating defects. These observations provide a broad understanding of the thermodynamics and phase transformations in BexZn1–xO alloys for the application of highly conductive and transparent oxide-based devices and fabrication of their alloy nanostructures.
Item Type: | Journal Article | ||||
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||
Journal or Publication Title: | ACS Applied Materials & Interfaces | ||||
Publisher: | American Chemical Society | ||||
ISSN: | 1944-8244 | ||||
Official Date: | 7 October 2014 | ||||
Dates: |
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Volume: | Volume 6 | ||||
Number: | Number 21 | ||||
Page Range: | pp. 18758-18768 | ||||
DOI: | 10.1021/am5043388 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access |
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