Browsing by Author "Chen, Tsung-Han"

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A Facile Surface Treatment Utilizing Binary Mixtures of Ammonium Salts and Polar Solvents for Multiply Enhancing Thermoelectric PEDOT: PSS Films
(2014-12-01)
Tsai, Tsung-Che
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Chen, Tsung-Han
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Chang, Hsiu-Cheng
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Chen, Chun-Hua
;
Huang, Yi-Chia
Architecture controlled synthesis of flower-like In2O3 nanobundles with significantly enhanced ultraviolet scattering and ethanol sensing
(2012)
Lai, Hsiang-Yu
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Chen, Tsung-Han
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Chen, Chun-Hua
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材料科學與工程學系
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Department of Materials Science and Engineering
We have successfully synthesized novel needle-like and flower-like In2O3 nanobundles (NBs) composed of numerous parallel assembled nanoparticle chains via hydrolysis of InCl3 with NaBH4 in aqueous solution and subsequent heat treatment. These previously unknown nanostructures exhibit unusual optical and ethanol sensing properties. T-matrix simulation evidently explains the assembling effect on the significant scattering of UV-visible spectra including a characteristic peak in the UV region as well as the broadened edge toward the visible region for these two NBs. The greatly enhanced ethanol-sensing properties observed for the flower-like In2O3 NBs indicate that the dominant factors for sensing are not only the nanoparticle size but also the structural dimension and architecture of the nanoassembly.
Carbon-Coated Porous Aluminum Oxides Used as Spacer Overlayers to Reduce Secondary Electron Emission for Field Emission Display Applications
(2013-07-01)
Yu, Tung-Yuan
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Pan, Fu-Ming
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Chen, Cheng-Li
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Chen, Te-Ming
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Chen, Tsung-Han
Porous surface structures can mitigate the charging effect of vacuum spacers of field-emission flat panel display due to the abundance of secondary electrons (SEs) emitted from the spacers during field emission display (FED) operation. In this study, we fabricated porous anodic aluminum oxide (AAO) overlayers on glass substrates to examine the effect of carbon deposition on the reduction of SE emissions. This paper reports that uniform AAO overlayers can be simultaneously prepared on both sides of a glass plate 2 x 10 cm(2) in size. The SE emission of the AAO overlayer was examined by using an Auger electron microscope. When a small amount of carbon is evaporation-deposited on the as-prepared AAO overlayer, the SE emission efficiency is significantly decreased and the reduction in the SE emission is ascribed to the low SE yield of the carbon deposit and the suppression of SE escape from the narrowed pore channels. However, a heavy deposition of carbon results in a smaller surface roughness of the AAO overlayer, thereby increasing SE emission. The carbon-coated AAO overlayer demonstrates favorable electrical and mechanical properties, making it suitable for use in FED vacuum spacers. (C) 2013 The Japan Society of Applied Physics
Dark current suppression of amorphous selenium based photosensors by the ZnO hole blocking layer
(2014-05-01)
Yu, Tung-Yuan
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Pan, Fu-Ming
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Chang, Cheng-Yi
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Hu, Tien
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Chen, Jenn-Fang
To study the influence of defects in the hole blocking layer (HBL) on the dark current of amorphous selenium (a-Se) based photosensors, we prepared ZnO thin films by reactive sputter deposition (RSD) for the use as the HBL of the photosensors. The ZnO HBL layers prepared with different oxygen flow rates were characterized by X-ray photoelectron spectroscopy, Raman scattering analysis and photoluminescence, indicating that the density of oxygen vacancies in the ZnO thin films is significantly affected by the oxygen flow rate. The deep level transient spectroscopy measurement reveals two hole trap levels present in the RSD deposited ZnO thin films; one is at 0.94 eV and the other at 0.24 eV above the valence band edge. The electrical performance of the a-Se photosensor is largely influenced by the amount of oxygen vacancies in the ZnO thin film. The a-Se photosensor with the ZnO HBL of the most oxygen vacancies has the lowest dark current and demonstrates the highest breakdown field. (C) 2014 Elsevier B.V. All rights reserved.
Enhanced thermoelectricity of three-dimensionally mesostructured BixSb2-xTe3 nanoassemblies: from micro-scaled open gaps to isolated sealed mesopores
(2017-03-07)
Chen, Tsung-Han
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Lin, Ping-Yu
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Chang, Hsiu-Cheng
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Chen, Chun-Hua
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材料科學與工程學系
We describe an innovative interfacial design concept and nanostructuring of novel BixSb2-xTe3 (BST) nanoassembled films comprising unique air-solid interfaces from micro-scaled open gaps to isolated sealed mesopores, and high-quality solid-solid ones including the coherent grain boundaries and specific twins, utilizing pulsed laser deposition (PLD), for potentially activating multiple thermoelectric enhancing mechanisms. The unusual mesopore embedded BST films exhibit the highest power factor of similar to 33 mu W cm(-1) K-2, which is comparable to or higher than the previously reported values for BST, and the corresponding relatively low thermal diffusivity in contrast to that for dense pore-less BST films evidently reveals the crucial role of the three-dimensionally and densely arranged air-solid interfaces in significantly arising the phonon scattering.
Functionalized Silica Nanoparticles by Nanometallic Ag Decoration for Optical Sensing of Organic Molecule
(2010-09-23)
Jean, Ren-Der
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Chiu, Kuo-Chuang
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Chen, Tsung-Han
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Chen, Chun-Hua
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Liu, Dean-Mo
Sensing technologies based on metallic nanoparticles, known as Ag, Au, and so on, have raised enormous interest for their extraordinary sensing resolution and sensitivity to analytes of chemical or biological importance under optical detection have received wide attention in recent decades. Currently, a discrete nanoparticle in a free-standing form, either being organically or biologically modified on the nanoparticle surface, on a given substrate surface region has been employed for photosensing purpose. However, metallic nanoparticles suffering from physical and chemical instability such as oxidation, interparticle coupling, agglomeration, and so on during the processing stages may render undesirable outcomes, which further results in poorer performance than the theoretical expectation. Here we propose a facile and elegant concept to prepare an Ag-decorated silica nanoparticle (hereinafter termed core-shell SiO(2)@Ag nanosphere) based on the modified Stober method. The Ag nanoparticles with an average size controlled at about 1, 3, and 5 nm deposited over the surface of the silica nanocarrier were well separated, making the resulting SiO(2)@Ag nanospheres. The nanospheres showed physically and optically stable surface plasmon resonance spectra and also demonstrated a relatively high Ag-sized dependent sensitivity to ppb level for the detection of analyte molecule, that is, melamine. Theoretical model fitting has been well managed to correlate the optical behavior of the nanosensors, and the outcomes strongly indicated a promising potential of the Ag-decorated SiO(2) core-shell nanospheres for sensory applications.
Laser co-ablation of bismuth antimony telluride and diamond-like carbon nanocomposites for enhanced thermoelectric performance
(2018-01-21)
Chen, Tsung-Han
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Chen, Po-Hung
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Chen, Chun-Hua
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材料科學與工程學系
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Department of Materials Science and Engineering
A novel design of thermoelectric hetero-nanocomposite films comprising well-aligned oriented (Bi,Sb)(2)Te-3 (BST) nanocrystals and randomly dispersed diamond-like carbon (DLC) clusters has been realized for the first time using dual-beam pulsed laser co-deposition on SiO2 insulated Si substrates. The simultaneously deposited DLC additives were found not only to successfully prevent the thermally induced rapid growth of BST for having consistent nanostructures across the whole BST: DLC film, but also to effectively reduce the thermal transport as qualitatively evidenced by micro-Raman characterizations. The significantly enhanced Seebeck coefficients up to 550 mV K-1 and the corresponding power factor of similar to 46 mu W cm(-1) K-2 revealed comparable to or higher than previously reported values for BST or BSTbased nanocomposites, which evidently originated from the presence of multiple BST:DLC heterointerfaces as clarified in the Pisarenko plot.
Optical and electrical properties of ink-jet printed indium-tin-oxide nanoparticle films
(2011-11-01)
Lai, Hsiang-Yu
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Chen, Tsung-Han
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Chen, Chun-Hua
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材料科學與工程學系
;
Department of Materials Science and Engineering
In this work, spherical indium tin oxide (ITO) nanoparticles (similar to 15 nm) synthesized by co-precipitation method were successfully applied for direct ink-jet printing of transparent conducting patterns on polyethylene terephthalate substrates. The printed ITO nanoparticle patterns with various thicknesses were investigated for understanding fundamental properties and potentials for soft electronics. It has been found that the optical transmittance in the visible region as well as the band-gap absorption edge of the printed ITO films significantly varies with thickness, which is related to the huge nanoparticle scattering effect as evidenced. The electrical resistivity can be effectively improved by increasing the pattern thickness, indicating that the present printed ITO films are of great potential for optoelectronic applications. (C) 2011 Elsevier B.V. All rights reserved.
Quasi two-dimensional carbon nanobelts synthesized using a template method
(2008-04-01)
Lin, Cheng-Te
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Chen, Tsung-Han
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Chin, Tsung-Shune
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Lee, Chi-Young
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Chiu, Hsin-Tien
Carbon nanobelts have been synthesized using nanoporous anodic alumina as template and ethanol as precursor. The length and width are tens of micrometers and 470 nm, respectively The thickness was measured to be 5 nm, exhibiting a high-aspect-ratio morphology. After annealing, the crystallinity of the nanobelts can be improved. The formation mechanism of such morphology is demonstrated as a radial deformation of large thin nanotubes. This is disclosed for the first time in the literature regarding the attainment of a quasi two-dimensional nanocarbon via a template route. Field emission measurements on the sample annealed at 800 degrees C show a turn-on voltage 3.25V/mu m and stable long-term emission efficiency The lower threshold voltage is attributed to the strong edge emitter effect. (C) 2008 Elsevier Ltd. All rights reserved.
Smart assembling of multi-scaled functional interfaces in thermoelectric Ga2Te3/Te hetero-nanocomposites
(2014-01-01)
Chang, Hsiu-Cheng
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Chiang, Ming-Hsiu
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Tsai, Tsung-Che
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Chen, Tsung-Han
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Whang, Wha-Tzong
We describe an innovative concept and facile approach in fabricating laterally assembled Ga2Te3/Te binary nanocomposite films, which comprise two-dimensional quasi-periodic Ga2Te3 nanoassemblies surrounded by interlocking highly-conductive Te single crystals for comprehensively establishing subnanoto micro-scaled multi-style versatile interfaces. The distinct Ga2Te3/Te nanocomposite film exhibits a power factor that is about 60 times higher than the reported conventional Ga2Te3 and Te materials, mainly due to the 2- to 3-order improved electrical conductivity and the comparable Seebeck coefficient.
Superassembling of Bi2Te3 hierarchical nanostructures for enhanced thermoelectric performance
(2015-01-01)
Chang, Hsiu-Cheng
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Chen, Tsung-Han
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Whang, Wha-Tzong
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Chen, Chun-Hua
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材料科學與工程學系
We describe a facile and one-step pulsed laser deposition (PLD) technique that was utilized for the first time to systematically fabricate a series of innovative Bi2Te3 superassembly-on-epitaxy bi-layer nanostructures, by uniquely coupling the upper self-assembled well-ordered Bi2Te3 hierarchical nanostructures with unusually high surface-and interface-to-volume ratios and a highly electrical conductive epitaxial bottom thin layer on insulated SiO2/Si substrates, as an emerging new class of the most advanced thermoelectric nanomaterials. The optimized power factor of the present superassembly-on-epitaxy films is one to three orders of magnitude higher than that of most Bi2Te3 nanoassemblies defined as the assemblies of nanocrystals, evidently proving the significance and potential of the present new concept and the resulting thermoelectric nanomaterials.
Transparent SiO2-Ag core-satellite nanoparticle assembled layer for plasmonic-based chemical sensors
(2012-05-28)
Chen, Tsung-Han
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Jean, Ren-Der
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Chiu, Kuo-Chuang
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Chen, Chun-Hua
;
Liu, Dean-Mo
We discovered a promising sensing capability of SiO2@Ag core-satellite nanoparticles with respect to organic melamine when they were consolidated into a solid-type thin-film entity. A series of theoretical models were proposed which provided calculation outcomes superior to those of existing models for the localized surface plasmon resonance spectra of the solid-state assemblies. We envisioned not only that such a SiO2@Ag film is a potential candidate for a transparent solid-state optical nanosensor for the detection of organic molecules but also that the resulting plasmonic resonance model facilitates a better understanding of such a solid-state nanosensor used for a number of sensory applications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4722583]