Browsing by Author "Niu, H."

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A compact biological cell irradiation system with a Van de Graaff accelerator
(2013-11-15)
Cho, I. C.
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Niu, H.
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Chen, C. H.
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Chou, W. T.
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Yu, Y. C.
This report describes the development of a compact microcell irradiation system in the 3 MV MN Van de Graaff accelerator in the Accelerator Laboratory of National Tsing Hua University (NTHU). The main feature of this system is backscattering, a technique whereby a 100 nm gold scattering foil is placed in the center of a scattering chamber, instead of a 90 bending magnet. The incident particles produced by the accelerator bombard the scattering foil and scatter isotropically. A set of micro pinholes was installed above the scattering foil and directed the 90 scattering particles to irradiate the cell target. This innovation simplifies the system design and massively reduces the cost and space requirements for system construction. (C) 2013 Elsevier B.V. All rights reserved.
A Novel Cell Irradiation System Using 90 degrees-Scattering Technique
(2011-02-01)
Cho, I. C.
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Weng, M. F.
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Wu, J. M.
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Chiang, S. Y.
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Chou, W. T.
A novel cell irradiation system was developed for use with the HVEE Van de Graaff accelerator at the National Tsing Hua University. A 90 degrees-scattering technique using an Au foil was designed, in which charged particles were directed from horizontal to vertical irradiation. Beam performance was tested with a silicon detector and a CR-39 nuclear track detector. The HeLa cells were irradiated with 2-MeV alpha particles and the formation of giant cells was observed. The result showed that this system provides a convenient way of generating a vertical particle beam and a cell-supporting chamber, thereby allowing a suitable cell growth condition during irradiation. Furthermore, establishment of such a system is more convenient and economical than the alternatives.
A Novel Cell Irradiation System Using Backscattering Technique
(2009-01-01)
Cho, I. C.
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Chen, C. H.
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Weng, M. F.
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Chiang, S. Y.
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Chou, W. T.
In this paper, we report a novel cell irradiation system at the HVEE Van de Graaff accelerator at National Tsing Hua University. The significant change of system design is use the backscattering technique to replace the 900 magnet which was widely used to derive beam direction from horizontal to vertical. A silicon barrier detector was used to measure the scattered particle energy. Meanwhile, nuclear track detector CR-39 was also applying in this study to assess the particle distribution at beam nozzle. The preliminary experiment performed by using 2 MeV alpha particle to irradiate the HeLa cell. The result showed, this system can provide an efficiently vertical particle beam irradiation and a standard growth condition during the period of irradiation. Furthermore, it's more economical and easier to set up than others.
Charged particle irradiation magnifies the DNA damage response in GBM cancer stem cell
(2013-01-01)
Cho, I-C.
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Niu, H.
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Chen, Y-W.
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Chen, C-H.
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Chou, W-T.
DNA double-strand breaks induced along the trajectory of particles
(2011-12-15)
Cho, I. C.
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Niu, H.
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Chen, C. H.
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Yu, Y. C.
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Hsu, C. H.
It is well-known that the DNA damage caused by charged particles considerably differs from damage due to electromagnetic radiation. In the case of irradiation by charged particles the DNA lesions are more complex and clustered. Such clustered damage is presumed difficult to be repaired, and is potentially lethal. In this study, we utilize a 90 degrees-scattering system and related imaging techniques to investigate the accumulation of gamma-H2AX along the trajectory of charged particles. By immunostaining the gamma-H2AX protein, optical images of corresponding double strand breaks were observed using a high resolution confocal microscope. We demonstrate the difference in the accumulation of gamma-H2AX from irradiation by 1 MeV protons and that of 150 key X-rays. The acquired images were arranged and reconstructed into a 3D image using ImageJ software. We discovered that the gamma-H2AX foci, following irradiation by protons, have a tendency to extend in the beam direction, while those from X-ray irradiation tend to be smaller and more randomly distributed. These results can be explained by the physical model of energy deposition. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.
Ferromagnetic GeMn thin film prepared by ion implantation and ion beam induced epitaxial crystallization annealing
(2012-06-11)
Chen, C. H.
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Niu, H.
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Yan, D. C.
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Hsieh, H. H.
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Lee, C. P.
Ferromagnetic GeMn was prepared by Mn implantation followed by ion beam-induced epitaxial crystallization annealing. The damage caused by Mn implantation was repaired by subsequent helium ion irradiation. Various structural analyses were performed and Mn ions were found to incorporate uniformly into the Ge lattice without the formation of any secondary phases. The remnant magnetic moment exhibited room temperature ferromagnetism. Anomalous Hall effect and field dependent magnetization were measured at the same time at room temperature indicating spin polarized free carrier transport. Additional measurement using x-ray magnetic circular dichroism also revealed that the carriers were spin-polarized. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729752]
Ion beam studies of InAs/GaAs quantum dots after annealing
(2008-04-01)
Niu, H.
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Chen, C. H.
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Wang, H. Y.
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Wu, S. C.
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Lee, C. P.
The microstructure changes of self-assembled InAs/GaAs quantum dots during RTA treatment was investigated using ion channeling and photoluminescence (PL). A small blueshift of the PL emission is observed for annealing temperatures of 650-800 degrees C and an obvious blueshift at 850 degrees C. The yield of channeled spectra decreased as annealing temperature was increased, but the yield increased while temperature above 800 degrees C in RTA. These results imply the strain of QD varied during RTA treatments. In addition, the As/Ga atomic ratio near the surface was determined from the surface peaks of the channeled spectrum. (c) 2008 Elsevier B.V. All rights reserved.
Local structure and magnetic properties of ferromagnetic GaMnAs made by helium ion induced epitaxial crystallization annealing
(2014-08-15)
Chen, C. H.
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Niu, H.
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Yan, D. C.
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Hsieh, H. H.
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Huang, R. T.
In this study we show GaMnAs preparation by Mn implantation in GaAs followed by helium ion beam induced epitaxial crystallization annealing. The characteristics of the Mn-implanted layer were investigated by X-ray diffraction, and transmission electron microscopy. The magnetic nature of the Mn-implanted layer was investigated with a superconducting quantum interference device. Structure analysis showed that Mn ions were incorporated substitutionally into the GaAs lattice without the formation of any detectable secondary phases. The remanent magnetic moment exhibited room temperature ferromagnetism. Additional measurement using X-ray magnetic circular dichroism also revealed that the carriers were spin polarized. (C) 2014 Elsevier B.V. All rights reserved.
Local structure and magnetic properties of ferromagnetic GaMnAs made by helium ion induced epitaxial crystallization annealing
(2014-08-15)
Chen, C. H.
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Niu, H.
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Yan, D. C.
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Hsieh, H. H.
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Huang, R. T.
In this study we show GaMnAs preparation by Mn implantation in GaAs followed by helium ion beam induced epitaxial crystallization annealing. The characteristics of the Mn-implanted layer were investigated by X-ray diffraction, and transmission electron microscopy. The magnetic nature of the Mn-implanted layer was investigated with a superconducting quantum interference device. Structure analysis showed that Mn ions were incorporated substitutionally into the GaAs lattice without the formation of any detectable secondary phases. The remanent magnetic moment exhibited room temperature ferromagnetism. Additional measurement using X-ray magnetic circular dichroism also revealed that the carriers were spin polarized. (C) 2014 Elsevier B.V. All rights reserved.
Local structure study of GeMn recrystallization process by helium ion beam-induced epitaxial crystallization
(2015-11-01)
Chen, C. H.
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Niu, H.
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Lee, C. P.
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this study, GeMn thin films were fabricated by implantation of Mn ions at room temperature. Post-annealing was performed using 2 MeV of He+ ion irradiation. The recrystallization phenomena of the GeMn thin films were analyzed by Raman scattering. High-resolution transmission electron microscopy was also used to characterize the recrystallization process before and after ion beam annealing. A structure phase transition-like behavior of the recrystallization process of GeMn thin films was observed in the Raman spectra. (C) 2015 Elsevier B.V. All rights reserved.
Rolling up Ge microtube from bare-Ge substrate
(2014-08-15)
Chen, C. H.
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Niu, H.
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Huang, R. T.
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Lee, C. P.
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奈米科技中心
We show Ge microtubes can be rolled-up from bare-Ge wafer at almost any position, once these films are released from its substrate. (C) 2014 Elsevier B.V. All rights reserved.
Rolling up Ge microtube from bare-Ge substrate
(2014-08-15)
Chen, C. H.
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Niu, H.
;
Huang, R. T.
;
Lee, C. P.
;
奈米科技中心
We show Ge microtubes can be rolled-up from bare-Ge wafer at almost any position, once these films are released from its substrate. (C) 2014 Elsevier B.V. All rights reserved.
Strain study of self-assembled InAs quantum dots by ion channeling technique
(2006-11-15)
Wang, Hsing-Yeh
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Lee, Chien-Ping
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Niu, H.
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Chen, C. H.
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Wu, S. -C.
Ion channeling technique using MeV C++ ions was used to study strain in self-assembled InAs quantum dots (QDs) buried in GaAs matrix. Because of the use of heavy ions, we were able to observe an angular shift in the angular scan of the In signal relative to that of the Ga/As signal. This provided a direct evidence that the InAs lattice is larger than that of GaAs in the growth direction. Combining the channeling results in [100] and [110] directions and the photoluminescence emission spectrum, we conclude that the InAs QDs are under tensile strain in the growth direction and have the same lattice constant as that of GaAs in the lateral direction. Thermal annealing causes the strain to relax, first in the growth direction and then in the lateral direction as the annealing temperature increases. The photoluminescence spectra of the QDs before and after annealing indicate, however, that composition intermixing also takes place during annealing and is the dominant factor in determining the band gap energy of the QDs. (c) 2006 American Institute of Physics.
The strain status of the buried self-assembled InAs quantum dots using MeV technique
(2006)
Wang, H. Y.
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Chen, C. H.
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Niu, H.
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Wu, S. C.
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Lee, C. P.
The strain status of the buried self-assembled InAs quantum dots was comprehended by measurement first time. Results show the in-plane strain is compressive and the lattice in the growth direction is lager than the lattice of GaAs. The strain of the sample annealed at 650 degrees C relaxes in the growth direction. The growth and the lateral direction become relaxed in the sample annealed at 750 degrees C.