Browsing by Issue Date, starting with "2014-08-13"

Now showing 1 - 20 of 25808

Porphyrin-Incorporated 2D D-A Polymers with Over 8.5% Polymer Solar Cell Efficiency
(2014-08-13)
Chao, YI-Hsiang
;
Jheng, Jyun-Fong
;
Wu, Jhong-Sian
;
Wu, Kuan-Yi
;
Peng, Hsih-Hao
Porphyrin-Incorporated 2D D-A Polymers with Over 8.5% Polymer Solar Cell Efficiency
(2014-08-13)
Chao, YI-Hsiang
;
Jheng, Jyun-Fong
;
Wu, Jhong-Sian
;
Wu, Kuan-Yi
;
Peng, Hsih-Hao
Temperature dependence of electronic behaviors in quantum dimension junctionless thin-film transistor
(2014-08-13)
Cheng, Ya-Chi
;
Chen, Hung-Bin
;
Han, Ming-Hung
;
Lu, Nan-Heng
;
Su, Jun-Ji
The high temperature dependence of junctionless (JL) gate-all-around (GAA) poly-Si thin-film transistors (TFTs) with 2-nm-thick nanosheet channel is compared with that of JL planar TFTs. The variation of SS with temperature for JL GAA TFTs is close to the theoretical value (0.2 mV/dec/K), owing to the oxidation process to form a 2-nm-thick channel. The bandgap of 1.35 eV in JL GAA TFTs by fitting experimental data exhibits the quantum confinement effect, indicating greater suppression of I-off than that in JL planar TFTs. The measured partial derivative V-th/partial derivative T of -1.34 mV/degrees C in JL GAA nanosheet TFTs has smaller temperature dependence than that of -5.01 mV/degrees C in JL planar TFTs.
Conducting Ag/oligothiophene complex pastes through a simple quenching/chelation method
(2014-08-14)
Lu, Fang-Hsien
;
Chang, Feng-Chih
;
Mohamed, Mohamed-Gamal
;
Liu, Tzeng-Feng
;
Chao, Chuen-Guang
This paper describes a simple and environmentally friendly approach-a facile, one-pot, quenching/ chelation method-for the fabrication of a silver paste in the form of Ag/oligothiophene complex composites. These Ag/oligothiophene complex composites possess excellent conductivities of 1.8 x 10(4) S cm(-1) in the bulk state and 6.08 x 10(2) S cm(-1) in the form of thin films. We have used X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) to characterize the microstructures of these novel Ag/oligothiophene complex composites.
Ferroelectric domain triggers the charge modulation in semiconductors (invited)
(2014-08-14)
Morozovska, Anna N.
;
Eliseev, Eugene A.
;
Ievlev, Anton V.
;
Varenyk, Olexander V.
;
Pusenkova, Anastasiia S.
We consider a typical heterostructure "domain patterned ferroelectric film-ultra-thin dielectric layer-semiconductor," where the semiconductor can be an electrolyte, paraelectric or multi-layered graphene. Unexpectedly, we have found that the space charge modulation profile and amplitude in the semiconductor, that screens the spontaneous polarization of a 180-deg domain structure of ferroelectric, depends on the domain structure period, dielectric layer thickness and semiconductor screening radius in a rather non-trivial nonlinear way. Multiple size effects appearance and manifestation are defined by the relationship between these three parameters. In addition, we show that the concept of effective gap can be introduced in a simple way only for a single-domain limit. Obtained analytical results open the way for understanding of current-AFM maps of contaminated ferroelectric surfaces in ambient atmosphere as well as explore the possibilities of conductivity control in ultra-thin semiconductor layers. (C) 2014 AIP Publishing LLC.
DISSOLUBLE PDMS-MODIFIED p(HEMA-MAA) AMPHIPHILIC COPOLYMER AND METHOD FOR FABRICATING THE SAME
(2014-08-14)
LIU Dean-Mo
;
HUANG Yun-Chun
;
HSU Chung-Yu
The present invention discloses a dissoluble PDMS-modified p(HEMA-MAA) amphiphilic copolymer and the method of fabricating the same. The amphiphilic copolymer of the present invention is fabricated via chemically bonding HEMA, MAA, and poly(dimethylsiloxane), bis(3-aminopropyl) terminated (PDMS) in aqueous solution. The PDMS-modified p(HEMA-MAA) amphiphilic copolymer can be dissolved completely in polar solvents, particularly alcohol solvents, to facilitate subsequent processing. The amphiphilic copolymer features adjustable hydrophobic-hydrophilic properties and exhibits excellent biocompatibility. Thus, it can be utilized in a number of advanced applications, including anti-fouling and drug delivery.
Conducting Ag/oligothiophene complex pastes through a simple quenching/chelation method
(2014-08-14)
Lu, Fang-Hsien
;
Chang, Feng-Chih
;
Mohamed, Mohamed-Gamal
;
Liu, Tzeng-Feng
;
Chao, Chuen-Guang
This paper describes a simple and environmentally friendly approach-a facile, one-pot, quenching/ chelation method-for the fabrication of a silver paste in the form of Ag/oligothiophene complex composites. These Ag/oligothiophene complex composites possess excellent conductivities of 1.8 x 10(4) S cm(-1) in the bulk state and 6.08 x 10(2) S cm(-1) in the form of thin films. We have used X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) to characterize the microstructures of these novel Ag/oligothiophene complex composites.
Multifunctionalities driven by ferroic domains
(2014-08-14)
Yang, J. C.
;
Huang, Y. L.
;
He, Q.
;
Chu, Y. H.
;
材料科學與工程學系
Considerable attention has been paid to ferroic systems in pursuit of advanced applications in past decades. Most recently, the emergence and development of multiferroics, which exhibit the coexistence of different ferroic natures, has offered a new route to create functionalities in the system. In this manuscript, we step from domain engineering to explore a roadmap for discovering intriguing phenomena and multifunctionalities driven by periodic domain patters. As-grown periodic domains, offering exotic order parameters, periodic local perturbations and the capability of tailoring local spin, charge, orbital and lattice degrees of freedom, are introduced as modeling templates for fundamental studies and novel applications. We discuss related significant findings on ferroic domain, nanoscopic domain walls, and conjunct heterostructures based on the well-organized domain patterns, and end with future prospects and challenges in the field. (C) 2014 AIP Publishing LLC.
Piezoelectric and piezomagnetic force microscopies of multiferroic BiFeO3-LiMn2O4 heterostructures
(2014-08-14)
Eshghinejad, Ahmad
;
Liang, Wen-I.
;
Chen, Qian Nataly
;
Ma, Feiyue
;
Liu, Yuanming
BiFeO3-LiMn2O4 (BFO-LMO) heterostructures were fabricated via pulsed laser deposition, and their ferroelectric and ferromagnetic properties were probed by magnetic force microscopy (MFM), piezoresponse force microscopy (PFM), and the newly developed piezomagnetic force microscopy (PmFM). MFM imaging shows no clear distinction between BFO and LMO phases, while PFM and PmFM mappings clearly distinguish LMO nanopillars from BFO matrix. Linear piezoelectric and piezomagnetic responses have been observed in both phases, with the effects more prominent in BFO. The strong piezomagnetic response in BFO is believed to arise from Mn doping, while piezoelectric-like response of LMO is attributed to ionic activities as well as vertical geometry of the heterostructure. The limitation of global excitation of PmFM is also discussed. (C) 2014 AIP Publishing LLC.
Ferroelectric domain triggers the charge modulation in semiconductors (invited)
(2014-08-14)
Morozovska, Anna N.
;
Eliseev, Eugene A.
;
Ievlev, Anton V.
;
Varenyk, Olexander V.
;
Pusenkova, Anastasiia S.
We consider a typical heterostructure "domain patterned ferroelectric film-ultra-thin dielectric layer-semiconductor," where the semiconductor can be an electrolyte, paraelectric or multi-layered graphene. Unexpectedly, we have found that the space charge modulation profile and amplitude in the semiconductor, that screens the spontaneous polarization of a 180-deg domain structure of ferroelectric, depends on the domain structure period, dielectric layer thickness and semiconductor screening radius in a rather non-trivial nonlinear way. Multiple size effects appearance and manifestation are defined by the relationship between these three parameters. In addition, we show that the concept of effective gap can be introduced in a simple way only for a single-domain limit. Obtained analytical results open the way for understanding of current-AFM maps of contaminated ferroelectric surfaces in ambient atmosphere as well as explore the possibilities of conductivity control in ultra-thin semiconductor layers. (C) 2014 AIP Publishing LLC.
Sub-10 fs spectroscopy of K-TCNQ crystal for observation of intramolecular vibration modulation in melting of the Peierls dimer
(2014-08-14)
Nakata, Kazuaki
;
Tokunaga, Eiji
;
Du, Juan
;
Xue, Bing
;
Miyazaki, Jun
K-TCNQ crystals show photoinduced phase transition (PIPT) between a Mott insulator and a spin Peierls (SP) phase, having T-c = 395 K (= and the crystal has T-c = 395 K of the PIPT). We report the intra-molecular vibrations in the excited K-TCNQ crystal after impulsive excitation using a sub 9.4 fs pulse laser in the reflection spectrum. The frequencies of the vibrations are close to the Raman frequencies of molecules. The frequencies increase with melting of the SP phase, and then decrease with rearrangement of the dimerization. In addition, the frequencies of the vibrations are time-resolved to be modulated by the intermolecular optical phonon with 510 fs period corresponding to 65 cm(-1). This modulation is associated with the periodical change of coupling strengths of intermolecular charge transfer and/or the dipolar coupling between the counterpart molecules in the neighboring chains.
Automated Segmentation and Quantification of White Matter Hyperintensities in Acute Ischemic Stroke Patients with Cerebral Infarction
(2014-08-15)
Tsai, Jang-Zern
;
Peng, Syu-Jyun
;
Chen, Yu-Wei
;
Wang, Kuo-Wei
;
Li, Chen-Hua
White matter hyperintensities (WMHs) of presumed vascular origin are common in ageing population, especially in patients with acute cerebral infarction and the volume has been reported to be associated with mental impairment and the risk of hemorrhage from antithrombotic agents. WMHs delineation can be computerized to minimize human bias. However, the presence of cerebral infarcts greatly degrades the accuracy of WMHs detection and thus limits the application of computerized delineation to patients with acute cerebral infarction. We propose a computer-assisted segmentation method to depict WMHs in the presence of cerebral infarcts in combined T1-weighted, fluid attenuation inversion recovery, and diffusion-weighted magnetic resonance imaging (MRI). The proposed method detects WMHs by empirical threshold and atlas information, with subtraction of white matter voxels affected by acute infarction. The method was derived using MRI from 25 hemispheres with WMHs only and 13 hemispheres with both WMHs and cerebral infarcts. Similarity index (SI) and correlation were utilized to assess the agreement between the new automated method and a gold standard visually guided semi-automated method done by an expert rater. The proposed WMHs segmentation approach produced average SI, sensitivity and specificity of 83.142 +/- 11.742, 84.154 +/- 16.086 and 99.988 +/- 0.029% with WMHs only and of 68.826 +/- 14.036, 74.381 +/- 18.473 and 99.956 +/- 0.054% with both WMHs and cerebral infarcts in the derivation cohort. The performance of the proposed method with an external validation cohort was also highly consistent with that of the experienced rater.
Urupocidin A: A New, Inducing iNOS Expression Bicyclic Guanidine Alkaloid from the Marine Sponge Monanchora pulchra
(2014-08-15)
Makarieva, Tatyana N.
;
Ogurtsova, Ekaterina K.
;
Denisenko, Vladimir A.
;
Dmitrenok, Pavel S.
;
Tabakmakher, Ksenya M.
Urupocidins A and B (1 and 2), bisguanidine alkaloids with an unprecedented skeleton system, derived from polyketide precursors and containing an unusual N-alkyl-N-hydroxyguanidine moiety, have been isolated from the sponge Monanhora pulchra. The structures of 1 and 2, including absolute configuration, were established using the detailed analysis of 1D and 2D NMR, CD, and mass spectra as well as chemical transformations. Compound 1 increases nitric oxide production in murine macrophages via inducing iNOS expression.
Contribution of thermal energy to initial ion production in matrix-assisted laser desorption/ionization observed with 2,4,6-trihydroxyacetophenone
(2014-08-15)
Lai, Yin-Hung
;
Chen, Bo-Gaun
;
Lee, Yuan Tseh
;
Wang, Yi-Sheng
;
Lin, Sheng Hsien
RATIONALE: Although several reaction models have been proposed in the literature to explain matrix-assisted laser desorption/ionization (MALDI), further study is still necessary to explore the important ionization pathways that occur under the high-temperature environment of MALDI. 2,4,6-Trihydroxyacetophenone (THAP) is an ideal compound for evaluating the contribution of thermal energy to an initial reaction with minimum side reactions. METHODS: Desorbed neutral THAP and ions were measured using a crossed-molecular beam machine and commercial MALDI-TOF instrument, respectively. A quantitative model incorporating an Arrhenius-type desorption rate derived from transition state theory was proposed. Reaction enthalpy was calculated using GAUSSIAN 03 software with dielectric effect. Additional evidence of thermal-induced proton disproportionation was given by the indirect ionization of THAP embedded in excess fullerene molecules excited by a 450 nm laser. RESULTS: The quantitative model predicted that proton disproportionation of THAP would be achieved by thermal energy converted from a commonly used single UV laser photon. The dielectric effect reduced the reaction Gibbs free energy considerably even when the dielectric constant was reduced under high-temperature MALDI conditions. With minimum fitting parameters, observations of pure THAP and THAP mixed with fullerene both agreed with predictions. CONCLUSIONS: Proton disproportionation of solid THAP was energetically favorable with a single UV laser photon. The quantitative model revealed an important initial ionization pathway induced by the abrupt heating of matrix crystals. In the matrix crystals, the dielectric effect reduced reaction Gibbs free energy under typical MALDI conditions. The result suggested that thermal energy plays an important role in the initial ionization reaction of THAP. Copyright (C) 2014 John Wiley & Sons, Ltd.
Rolling up Ge microtube from bare-Ge substrate
(2014-08-15)
Chen, C. H.
;
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.
Enhanced charge transfer character of photoexcited states of dye sensitizer on the N719/TiO2 interface as revealed by electroabsorption spectra
(2014-08-15)
Awasthi, Kamlesh
;
Hsu, Hung-Yu
;
Diau, Eric Wei-Guang
;
Ohta, Nobuhiro
;
應用化學系
Electroabsorption (E-A) spectra of (Bu4N)(2)[Ru(dcbpyH)(2)(NCS)(2)] (N719) sensitized on TiO2 nanoparticles are very different from those of the N719 solid film. In contrast with N719 fixed in a solid form, N719 adsorbed on TiO2 shows a significant electric field effect on absorbance, indicating the strong interaction in the surface between N719 and TiO2. The magnitude of the change in electric dipole moment following absorption of N719 sensitized on TiO2 is much greater than that of the sold film, suggesting that the interfacial charge transfer occurs following photoexcitation of N719 adsorbed on TiO2 surface. (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.
;
Niu, H.
;
Yan, D. C.
;
Hsieh, H. H.
;
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.
400-Gb/s Transmission Over 10-km SSMF Using Discrete Multitone and 1.3-mu m EMLs
(2014-08-15)
Chan, Trevor
;
Lu, I-Cheng
;
Chen, Jyehong
;
Way, Winston I.
;
光電工程學系
We experimentally demonstrated 400-Gb/s transmission over 10-km standard single-mode using discrete multi-tone (DMT) and four 1.3-mu m local-area-network wavelength-division-multiplexed externally modulated lasers. A reasonably good system margin has been obtained. We have also investigated the fundamental limitations of using semiconductor optical amplifiers for DMT-based systems.
Contribution of thermal energy to initial ion production in matrix-assisted laser desorption/ionization observed with 2,4,6-trihydroxyacetophenone
(2014-08-15)
Lai, Yin-Hung
;
Chen, Bo-Gaun
;
Lee, Yuan Tseh
;
Wang, Yi-Sheng
;
Lin, Sheng Hsien
RATIONALE: Although several reaction models have been proposed in the literature to explain matrix-assisted laser desorption/ionization (MALDI), further study is still necessary to explore the important ionization pathways that occur under the high-temperature environment of MALDI. 2,4,6-Trihydroxyacetophenone (THAP) is an ideal compound for evaluating the contribution of thermal energy to an initial reaction with minimum side reactions. METHODS: Desorbed neutral THAP and ions were measured using a crossed-molecular beam machine and commercial MALDI-TOF instrument, respectively. A quantitative model incorporating an Arrhenius-type desorption rate derived from transition state theory was proposed. Reaction enthalpy was calculated using GAUSSIAN 03 software with dielectric effect. Additional evidence of thermal-induced proton disproportionation was given by the indirect ionization of THAP embedded in excess fullerene molecules excited by a 450 nm laser. RESULTS: The quantitative model predicted that proton disproportionation of THAP would be achieved by thermal energy converted from a commonly used single UV laser photon. The dielectric effect reduced the reaction Gibbs free energy considerably even when the dielectric constant was reduced under high-temperature MALDI conditions. With minimum fitting parameters, observations of pure THAP and THAP mixed with fullerene both agreed with predictions. CONCLUSIONS: Proton disproportionation of solid THAP was energetically favorable with a single UV laser photon. The quantitative model revealed an important initial ionization pathway induced by the abrupt heating of matrix crystals. In the matrix crystals, the dielectric effect reduced reaction Gibbs free energy under typical MALDI conditions. The result suggested that thermal energy plays an important role in the initial ionization reaction of THAP. Copyright (C) 2014 John Wiley & Sons, Ltd.
Rolling up Ge microtube from bare-Ge substrate
(2014-08-15)
Chen, C. H.
;
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.