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Ki D.-K.,Pohang University of Science and Technology | Nam S.-G.,Pohang University of Science and Technology | Lee H.-J.,Pohang University of Science and Technology | Lee H.-J.,National Center for Nanomaterials Technology | Ozyilmaz B.,National University of Singapore
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

By using four-terminal configurations, we investigated the dependence of longitudinal and diagonal resistances of a graphene p-n interface on the quantum-Hall edge-state equilibration position. The resistance of a p-n device in our four-terminal scheme is asymmetric with respect to the zero point where the filling factor (ν) of the entire graphene vanishes. This resistance asymmetry is caused by the chiral direction dependent change in the equilibration position and leads to a deeper insight into the equilibration process of the quantum-Hall edge-states in a bipolar graphene system. © 2010 The American Physical Society. Source


Lee G.-H.,Pohang University of Science and Technology | Jin Y.-D.,Pohang University of Science and Technology | Lee H.-J.,Pohang University of Science and Technology | Lee H.-J.,National Center for Nanomaterials Technology
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We investigated the thermal-depinning current (Ic) distribution of Josephson vortices (JVs) in naturally stacked Bi2 Sr2 CaCu2 O8+δ intrinsic Jospehson junctions in tesla-range magnetic fields and at different field tilt angles from the in-plane position. The Ic distribution in the thermal-activation regime contains accurate information on the bias and magnetic-field dependence of the Josephson-vortex pinning potential. In a few-tesla-range magnetic field, JVs in a row in a junction, strongly coupled with each other, are pinned or depinned like a single physical entity at a single pinning center. In the best-aligned in-plane magnetic field, the edge pinning is most relevant and is insensitive to the field strength. In the presence of pancake vortices (PVs) in a slightly tilted field, however, the PV pinning deepens the JV pinning potential linearly with the number of PVs. © 2010 The American Physical Society. Source


Lee S.W.,Korea Atomic Energy Research Institute | Jun Y.K.,National Center for Nanomaterials Technology | Kwon O.Y.,POSCO
Journal of the Korean Physical Society | Year: 2011

A neutron grating interferometer has been developed and implemented for phase-contrast and dark-field imaging experiments on a thermal neutron beamline at the Ex-core Neutron irradiation Facility (ENF) at High-flux Advanced Neutron Application Reactor (HANARO), a 30 MW multipurpose research reactor. The gratings were designed and fabricated to function optimally at a neutron wavelength of 4.4 Å while Beryllium filters were used to shape the beam spectrum by cutting off wavelengths below 4 Å. The average visibility over the grating area was measured at ~10%. Neutron dark-field imaging experiments were performed to visualize magnetic domains in a Fe-3% Si sheet in a variety of orientations. Source


Park K.,University of Washington | Zhang Q.,University of Washington | Garcia B.B.,University of Washington | Zhou X.,University of Washington | And 2 more authors.
Advanced Materials | Year: 2010

(Figure Presented) An ultrathln TiO2 layer is successfully coated on the surface of sub-micrometersized aggregates of ZnO nanocrystallites through the atomic layer deposition (ALD) technique. The ZnO core/TiO 2 shell structure increases the open-circuit voltage, without impairing the photocurrent density and results in an increased power conversion efficiency from 5.2% to 6.3%. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Sohn C.-W.,Pohang University of Science and Technology | Rim T.-U.,Pohang University of Science and Technology | Choi G.-B.,Pohang University of Science and Technology | Jeong Y.-H.,Pohang University of Science and Technology | Jeong Y.-H.,National Center for Nanomaterials Technology
IEEE Transactions on Electron Devices | Year: 2010

In this paper, we propose an analytic model for inverted-staggered organic thin-film transistors, and we use the proposed model to investigate the dependence of contact effect on the voltage bias, the film thickness of the organic semiconductor, and the channel length. In our model, the variable-range-hopping transport is adopted for the conduction in the horizontal direction to the semiconductorinsulator interface, and the space-charge-limited conduction is adopted for the conduction in the vertical direction by considering the molecular orientations. Qualitative agreement is obtained between simulation and measurement in the steady-state characteristics. From simulation study, we notice that the contact resistances vary with the sourcegate voltage and with the sourcedrain voltage, the film thickness requires to be optimized to improve the on-current and the linearity in the linear operating regime, and the overlap length between the gate electrode and the source/drain contact needs to be guaranteed for the short-channel devices because it would not be scaled as much as the channel length. © 2010 IEEE. Source

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