Search

Your search keyword '"Chan, H. L. W."' showing total 809 results
Start Over Author "Chan, H. L. W."
809 results on '"Chan, H. L. W."'

1. Heteroepitaxial Growth and Multiferroic Properties of Mn-doped BiFeO3 films on SrTiO3 buffered III-V Semiconductor GaAs

Author

Gao, G. Y., Yang, Z. B., Huang, W., Zeng, H. Z., Wang, Y., Chan, H. L. W., Wu, W. B., and Hao, J. H.

Subjects
Condensed Matter - Materials Science
Abstract

Epitaxial Mn-doped BiFeO3 (MBFO) thin films were grown on GaAs (001) substrate with SrTiO3 (STO) buffer layer by pulsed laser deposition. X-ray diffraction results demonstrate that the films show pure (00l) orientation, and MBFO(100)//STO(100), whereas STO (100)//GaAs (110). Piezoresponse force microscopy images and polarization versus electric field loops indicate that the MBFO films grown on GaAs have an effective ferroelectric switching. The MBFO films exhibit good ferroelectric behavior (2Pr ~ 92 {\mu}C/cm2 and 2EC ~ 372 kV/cm). Ferromagnetic property with saturated magnetization of 6.5 emu/cm3 and coercive field of about 123 Oe is also found in the heterostructure at room temperature., Comment: 19 pages, 4 figures

Published
2013
Full Text
View/download PDF

2. Ferroelectric Domain Morphology Evolution and Octahedral Tilting in Lead-Free (Bi1/2Na1/2)TiO3-(Bi1/2K1/2)TiO3-(Bi1/2Li1/2)TiO3-BaTiO3 Ceramics at Different Temperatures

Author

Tai, Cheuk W., Choy, S. H., and Chan, H. L. W.

Subjects
Condensed Matter - Materials Science
Abstract

Observations by in-situ transmission electron microscopy (TEM) reveal the changes in domains morphology in 0.885(Bi1/2Na1/2)TiO3-0.05(Bi1/2K1/2)TiO3-0.015(Bi1/2Li1/2)TiO3-0.05BaTiO3 ceramics. Evolution of the macroscopic ferroelectric domains has been observed at 25 oC to 180 oC. The ferroelectric domains and their walls reduce progressively with increasing temperature. In the selected-area electron diffraction (SAED) patterns the crystallographic evidence of antiferroelectric domain is not found over the temperature range, which provides the evidence that the ferroelectric-antiferroelectric transition does not occur in the ceramic. The temperature-dependent forbidden 3/2 1/2 0 and superstructure 3/2 1/2 1/2 reflections indicate the presence of an in-phase and anti-phase octahedral tilting in the ceramic, respectively. Dark-field TEM images show that the size of the octahedral tilted domains is smaller than 30 nm across and these domains are uniformly distributed in the grains. The influence of the localized octahedral titling on the stability of ferroelectric domains and the temperature-dependent properties is discussed in this paper., Comment: 26 pages, 7 figures, 1 Table

Published
2011

3. Enhanced Ferromagnetic Ordering in GdBaCo$_{2}$O$_{5.5+\delta}$ Films on SrTiO3 (001) Substrate

Author

Wang, G. Y., Zhou, X. Y., Zheng, R. K., Hu, Y. M., Chan, H. L. W., and Wang, Y.

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Materials Science
Abstract

The authors investigated the structure and properties of GdBaCo$_{2}$O$_{5.5+\delta}$ thin films epitaxially grown on SrTiO$_{3}$ (001) single crystal substrates. The thin films were found to have a notable remnant magnetization above room temperature, which is much higher than that observed in bulk material. Transmission electron microscopy and x-ray diffraction patterns reveal that phase separation occurs in these films, and the phase responsible for the enhanced ferromagnetic order is $a$-oriented. The enhanced ferromagnetic order is attributed to the enhanced orbital order of Co$^{3+}$ in CoO$_{5}$ pyramids, and the disappearance of ferromagnetic to antiferromagnetic transition is explained the stabilization of higher spin state of Co$^{3+}$ in CoO$_{6}$ octahedra., Comment: 4 pages, 4 figures

Published
2009

47. The structural and in-plane dielectric/ferroelectric properties of the epitaxial (Ba, Sr)(Zr, Ti)O3 thin films.

Author

Chan, N. Y., Wang, D. Y., Wang, Y., Dai, J. Y., and Chan, H. L. W.

Subjects
DIELECTRIC properties, THIN films, EPITAXIAL layers, CURIE temperature, THIN film deposition
Abstract

Epitaxial (Ba1-xSrx)(Zr0.1Ti0.9)O3 (BSZT, x=0 – 0.45) thin films were deposited on (LaAlO3)0.3 (Sr2AlTaO6)0.35 (LSAT) substrates by pulsed laser deposition. The experimental results demonstrate that the structural, dielectric, and ferroelectric properties of the BSZT thin films were greatly dependent on the strontium content. The BSZT thin films transformed from tetragonal to cubic phase when x≥0.35 at room temperature. The Curie temperature and room-temperature remnant polarization decrease with increasing strontium concentration. The optimal dielectric properties were found in (Ba0.55Sr0.45)(Zr0.1Ti0.9)O3 thin films which is in paraelectric state, having tunability of 47% and loss tangent of 0.0338 under an electric field of 20 MV/m at 1MHz. This suggests that BSZT thin film is a promising candidate for tunable microwave device applications. [ABSTRACT FROM AUTHOR]

Published
2014
Full Text
View/download PDF

50. Tunable strain effect and ferroelectric field effect on the electronic transport properties of La0.5Sr0.5CoO3 thin films.

Author

Zhu, Q. X., Wang, W., Zhao, X. Q., Li, X. M., Wang, Y., Luo, H. S., Chan, H. L. W., and Zheng, R. K.

Subjects
EPITAXY, PIEZOELECTRICITY, PYROELECTRICITY, CRYSTALLOGRAPHY, THIN films
Abstract

Tensiled La0.5Sr0.5CoO3 (LSCO) thin films were epitaxially grown on piezoelectric 0.67Pb (Mg1/3Nb2/3)O3-0.33PbTiO3 (PMN-PT) single-crystal substrates. Due to the epitaxial nature of the interface, the lattice strain induced by ferroelectric poling or the converse piezoelectric effect in the PMN-PT substrate is effectively transferred to the LSCO film and thus reduces the tensile strain of the film, giving rise to a decrease in the resistivity of the LSCO film. We discuss these strain effects within the framework of the spin state transition of Co3+ ions and modification of the electronic bandwidth that is relevant to the induced strain. By simultaneously measuring the strain and the resistivity, quantitative relationship between the resistivity and the strain was established for the LSCO film. Both theoretical calculation and experimental results demonstrate that the ferroelectric field effect at room temperature in the LSCO/PMN-PT field-effect transistor is minor and could be neglected. Nevertheless, with decreasing temperature, the ferroelectric field effect competes with the strain effect and plays a more and more important role in influencing the electronic transport properties of the LSCO film, which we interpreted as due to the localization of charge carriers at low temperature. [ABSTRACT FROM AUTHOR]

Published
2012
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results