ORCID Profile
0000-0001-5396-2439
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Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3CE42011F
Abstract: Pinning effect on crystalline Be x Zn 1−x O alloy films on Al 2 O 3 (0001).
Publisher: AIP Publishing
Date: 07-04-2014
DOI: 10.1063/1.4870533
Abstract: The influence of growth temperature on the synthesis of BexZn1−xO alloy films, grown on highly-mismatched Al2O3(0001) substrates, was studied by synchrotron x-ray scattering, high-resolution transmission electron microscopy and photoluminescence measurements. A single-phase BexZn1−xO alloy with a Be concentration of x = 0.25, was obtained at the growth temperature, Tg = 400 °C, and verified by high-resolution transmission electron microscopy. It was found that high-temperature growth, Tg≥600 °C, caused phase separation, resulting in a random distribution of intermixed alloy phases. The inhomogeneity and structural fluctuations observed in the BexZn1−xO films grown at high temperatures are attributed to a variation in Be composition and mosaic distribution via atomic displacement and strain relaxation.
Publisher: American Chemical Society (ACS)
Date: 21-10-2014
DOI: 10.1021/AM5043388
Abstract: We investigate the effect of thermally induced phase transformations on a metastable oxide alloy film, a multiphase Be(x)Zn(1-x)O (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 0.31 m0 and 0.67 m0. A conductivity as high as 1.4 × 10(3) S · cm(-1) is attained, corresponding to the carrier concentration n(Int) = 2.16 × 10(20) 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 Be(x)Zn(1-x)O alloys for the application of highly conductive and transparent oxide-based devices and fabrication of their alloy nanostructures.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Aleksander Krupski.