Browsing by Issue Date, starting with "2015-02-06"

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Designer germanium quantum dot phototransistor for near infrared optical detection and amplification
(2015-02-06)
Kuo, M. H.
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Lai, W. T.
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Hsu, T. M.
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Chen, Y. C.
;
Chang, C. W.
We demonstrated a unique CMOS approach for the production of a high-performance germanium (Ge) quantum dot (QD) metal-oxide-semiconductor phototransistor. In the darkness, low off-state leakage (I-off similar to 0.27 pA mu m(-2)), a high on-off current ratio (I-on/I-off similar to 10(6)), and good switching behaviors (subthreshold swing of 175 mV/dec) were measured on our Ge-QD phototransistor at 300 K, indicating good hetero-interfacial quality of the Ge-on-Si. Illumination makes a significant enhancement in the drain current of Ge QD phototransistors when biased at both the on-and off-states, which is a great benefit from Ge QD-mediated photoconductive and photovoltaic effects. The measured photocurrent-to-dark-current ratio (I-photo/I-dark) and the photoresponsivities from the Ge QD phototransistor are as high as 4.1 x 10(6) and 1.7 AW(-1), respectively, under an incident power of 0.9mW at 850 nm illumination. A superior external quantum efficiency of 240% and a very fast temporal response time of 1.4 ns suggest that our Ge QD MOS phototransistor offers great promise as optical switches and transducers for Si-based optical interconnects.
Ultrafast Multi-Level Logic Gates with Spin-Valley Coupled Polarization Anisotropy in Monolayer MoS2
(2015-02-06)
Wang, Yu-Ting
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Luo, Chih-Wei
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Yabushita, Atsushi
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Wu, Kaung-Hsiung
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Kobayashi, Takayoshi
The inherent valley-contrasting optical selection rules for interband transitions at the K and K' valleys in monolayer MoS2 have attracted extensive interest. Carriers in these two valleys can be selectively excited by circularly polarized optical fields. The comprehensive dynamics of spin valley coupled polarization and polarized exciton are completely resolved in this work. Here, we present a systematic study of the ultrafast dynamics of monolayer MoS2 including spin randomization, exciton dissociation, free carrier relaxation, and electron-hole recombination by helicity- and photon energy-resolved transient spectroscopy. The time constants for these processes are 60 fs, 1 ps, 25 ps, and, similar to 300 ps, respectively. The ultrafast dynamics of spin polarization, valley population, and exciton dissociation provides the desired information about the mechanism of radiationless transitions in various applications of 2D transition metal dichalcogenides. For example, spin valley coupled polarization provides a promising way to build optically selective-driven ultrafast valleytronics at room temperature. Therefore, a full understanding of the ultrafast dynamics in MoS2 is expected to provide important fundamental and technological perspectives.
Microwave-granular activated carbon (MW-GAC) system for carbofuran degradation: Analysis of characteristics and recyclability of the spent GAC
(2015-02-06)
Remya, Neelancherry
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Lin, Jih-Gaw
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環境工程研究所
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Institute of Environmental Engineering
Granular activated carbon (GAC) is frequently used to remove pollutants from wastewater. However, the mechanism of pollutant removal by GAC is by adsorption and hence spent GAC should be regenerated and used for several cycles for minimizing the cost of treatment. In the present study, the characteristics of GAC and carbofuran removal mechanism were explored in a microwave-GAC (MW-GAC) system. Carbofuran removal by adsorption was 52% at a GAC loading of 0.8g/L. However, complete carbofuran degradation from aqueous solution as well as from GAC surface was obtained within 30min in a MW-GAC system. In addition, A COD removal efficiency of 72% was observed in the MW-GAC system at pH 8 and 80 degrees C after 30min. The degradation occurred mainly through cleavage of carbamate group and oxidation of furan ring. Carbofuran removal by adsorption was enhanced with MW exposed GAC due to the improvement in the surface property on exposure to MW. On the other hand, recyclability of MW exposed GAC in the MW-GAC system indicated > 99% degradation of carbofuran in all the three cycles tested. As a whole, complete degradation of carbofuran and the effective recycling of the spent GAC could be achieved in the MW-GAC system.
Improvement of light quality by DBR structure in white LED
(2015-02-09)
Lin, Huang-Yu
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Chen, Kuo-Ju
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Wang, Sheng-Wen
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Lin, Chien-Chung
;
Wang, Kuan-Yu
This study demonstrates the application of DBR structure into the remote phosphor structure to improve the angular correlated color temperature (CCT) deviation in white light-emitting diodes (WLEDs). In the experiment, the LED device with DBR structure yielded a higher luminous efficiency than a conventional structure. The CCT deviation can be improved from 1758K to 280K in a range of -70 to 70 degree and the luminous flux increases more than 10% due to the enhancement of the light extraction of the blue light. Moreover, the reflectance of the different DBR structures is analyzed with different angles to reveal the reasons of such improvements. As the result, this LED device with DBR structure shows the great potential to use as the next generation lighting source. (C) 2014 Optical Society of America
Approaching conversion limit with all-dielectric solar cell reflectors
(2015-02-09)
Fu, Sze Ming
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Lai, Yi-Chun
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Tseng, Chi Wei
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Yan, Sheng Lun
;
Zhong, Yan Kai
Metallic back reflectors has been used for thin-film and wafer-based solar cells for very long time. Nonetheless, the metallic mirrors might not be the best choices for photovoltaics. In this work, we show that solar cells with all-dielectric reflectors can surpass the best-configured metal-backed devices. Theoretical and experimental results all show that superior large-angle light scattering capability can be achieved by the diffuse medium reflectors, and the solar cell J-V enhancement is higher for solar cells using all-dielectric reflectors. Specifically, the measured diffused scattering efficiency (D.S.E.) of a diffuse medium reflector is >0.8 for the light trapping spectral range (600nm-1000nm), and the measured reflectance of a diffuse medium can be as high as silver if the geometry of embedded titanium oxide(TiO2) nanoparticles is optimized. Moreover, the diffuse medium reflectors have the additional advantage of room-temperature processing, low cost, and very high throughput. We believe that using all-dielectric solar cell reflectors is a way to approach the thermodynamic conversion limit by completely excluding metallic dissipation. (C) 2015 Optical Society of America
Design and demonstration of high efficiency anti-glare LED luminaires for indoor lighting
(2015-02-09)
Chiang, Che-Wen
;
Hsu, Yu-Kai
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Pan, Jui-Wen
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光電系統研究所
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照明與能源光電研究所
An anti-glare luminaire design is proposed to reduce the effect of glare and the multi-shadow while preserving high optical efficiency, high illumination uniformity and low unified glare rating (UGR). Comparison to the traditional direct light emitting diode (LED) luminaire in optical simulations showed an enhancement of the illumination uniformity from 64.9% to 80.0%. The optical efficiency was 79.5%, and the UGR value was controlled under 18.8. For the actual measurement, the finished product had an illumination uniformity of 77.0%, optical efficiency of 76.0%, UGR value of 19.0, and efficacy of 81.4 lm/w. Through this design, the lighting performance was greatly enhanced. (C) 2014 Optical Society of America
Anisotropic exciton relaxation in nanostructured metal (Zn and F16Zn)-phthalocyanine
(2015-02-09)
Ahn, Hyeyoung
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Liou, Wei-Hyun
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Chen, Huang-Ming Philip
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Hsu, Chia-Hung
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光電工程學系
We report ultrafast excited state dynamics of zinc phthalocyanine and zinc hexadecafluoro phthalocyanine thin films which have nanorod-like structures. Excitons in the singlet states undergo multi-exponential relaxation processes to the ground state and the singlet lifetime within a few tens of picoseconds is attributed to the diffusion-limited exciton annihilation process. Diffusive migration of the singlet excitons shows the anisotropic lifetimes depending on the polarization of probe beam. Similar anisotropy is observed in the X-ray diffraction data which exhibits long-range alignment of molecular columns along the long axis of nanorod, whereas disordered arrangement in lateral direction to the axis of nanorod. (C) 2015 Optical Society of America
Simultaneous dual-wavelength imaging of nonfluorescent tissues with 3D subdiffraction photothermal microscopy
(2015-02-09)
Miyazaki, Jun
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Tsurui, Hiromichi
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Kawasumi, Koshi
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Kobayashi, Takayoshi
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電子物理學系
Multi-wavelength microscopic imaging is essential to visualize a variety of nanoscale cellular components with high specificity and high spatial resolution. However, previous techniques are based on fluorescence, and thus cannot visualize nonfluorescent species, which are much less suffered from photodamage or photobleaching and hence are intrinsically useful in wider range of optical microscopy. Here, we show that simultaneous multi-wavelength imaging of nonfluorescent species can be achieved with the use of a photothermal microscope. Dual-wavelength subdiffraction imaging of biological tissues stained with hematoxylin and eosin is demonstrated. Three-dimensional label-free imaging of mouse melanoma tissue section is also presented to demonstrate the effectiveness of the enhanced spatial resolution. Our technique can be implemented using cost-effective and compact laser diodes and is applicable for various types of both fluorescent and nonfluorescent tissues. (C) 2015 Optical Society of America
Electric connecting structure comprising preferred oriented Cu6Sn5 grains and method for fabricating the same
(2015-02-10)
Chen Chih
;
Lin Han-Wen
An electric connecting structure comprising preferred oriented Cu6Sn5 grains and a method for fabricating the same are disclosed. The method of the present invention comprises steps: (A) providing a first substrate; (B) forming a first nano-twinned copper layer on part of a surface of the first substrate; (C) using a solder to connect the first substrate with a second substrate having a second electrical pad, in which the second electrical pad comprises a second nano-twinned copper layer, and the solder locates between the first nano-twinned copper layer and the second nano-twinned copper layer; and (D) reflowing at the temperature of 200° C. to 300° C. to transform at least part of the solder into an intermetallic compound (IMC) layer, in which the IMC layer comprises plural Cu6Sn5 grains with a preferred orientation; wherein at least 50% in volume of the first and second nano-twinned copper layer comprises plural grains.
Submicron connection layer and method for using the same to connect wafers
(2015-02-10)
Chen Kuan-Neng
;
Chang Yao-Jen
A submicron connection layer and a method for using the same to connect wafers is disclosed. The connection layer comprises a bottom metal layer formed on a connection surface of a wafer, an intermediary diffusion-buffer metal layer formed on the bottom metal layer, and a top metal layer formed on the intermediary diffusion-buffer metal layer. The melting point of the intermediary diffusion-buffer metal layer is higher bottom metal layers may form a eutectic phase. During bonding wafers, two top metal layers are joined in a liquid state; next the intermediary diffusion-buffer metal layers are distributed uniformly in the molten top metal layers; then the top and bottom metal layers diffuse to each other to form a low-resistivity eutectic intermetallic compound until the top metal layers are completely exhausted by the bottom metal layers.
License plate recognition system and method
(2015-02-10)
Wu Bing-Fei
;
Chen Yen-Lin
;
Huang Hao-Yu
;
Lin Hsin-Yu
A license plate recognition system and method recognizes a license plate attached to a vehicle and bears a license plate number. The system includes a database module, a reducing module, an image capturing unit, a sorting unit, and a recognizing module. The database module stores license plate position sample type-related data and license plate number sample type-related data whose quantity is reducible by the reducing module. The image capturing unit captures license plate images at different imaging resolutions to generate license plate position image eigenvalue and license plate number image eigenvalue. The sorting unit computes the license plate position image eigenvalue to generate license plate position type-related data and computes the license plate number image eigenvalue to generate license plate number type-related data. The recognizing module compares the license plate number type-related data with the license plate number sample type-related data, thereby recognizing the license plate number.
Outlier detection from vehicle trajectories to discover roaming events
(2015-02-10)
Shen, Minxin
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Liu, Duen-Ren
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Shann, Shi-Han
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資訊管理與財務金融系註：原資管所+財金所
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Department of Information Management and Finance
Roaming, referring to the behavior of repeated observation of intended crime scenes before committing crimes, is a suspicious pattern often mentioned by experienced police investigators, but still remains a vague concept which needs to be well realized in video surveillance systems. This work first describes the scenario of roaming behaviors related to planned crimes, and then derives formal specifications for detecting suspicious roaming events from vehicle trajectories. Consequently, algorithms are designed for rapidly sorting out potential outliers and thoroughly examining their suspicious intention through circling activities, relative driving speed and time dispersion. Roaming trajectories and relevant trajectories are finally grouped into events and appropriately ranked. Furthermore, preliminary experiments and illustrative examples on synthetic data demonstrate the feasibility of our methods. The proposed approach enhances conventional vehicle plate analysis so that it becomes capable of discovering complex criminal behaviors and hence increasing investigation performance and decision quality. (C) 2014 Elsevier Inc. All rights reserved.
Exploring the Impacts of Cognitive and Metacognitive Prompting on Students\' Scientific Inquiry Practices Within an E-Learning Environment
(2015-02-11)
Zhang, Wen-Xin
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Hsu, Ying-Shao
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Wang, Chia-Yu
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Ho, Yu-Ting
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教育研究所
This study explores the effects of metacognitive and cognitive prompting on the scientific inquiry practices of students with various levels of initial metacognition. Two junior high school classes participated in this study. One class, the experimental group (n = 26), which received an inquiry-based curriculum with a combination of cognitive and metacognitive prompts, was compared to the other class, the comparison group (n = 25), which received only cognitive prompts in the same curriculum. Data sources included a test of inquiry practices, a questionnaire of metacognition, and worksheets. The results showed that the mixed cognitive and metacognitive prompts had significant impacts on the students\' inquiry practices, especially their planning and analyzing abilities. Furthermore, the mixed prompts appeared to have a differential effect on those students with lower level metacognition, who showed significant improvement in their inquiry abilities. A combination of cognitive and metacognitive prompts during an inquiry cycle was found to promote students\' inquiry practices.
The muon system of the Daya Bay Reactor antineutrino experiment
(2015-02-11)
An, F. P.
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Balantekin, A. B.
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Band, H. R.
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Beriguete, W.
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Bishai, M.
The Daya Bay experiment consists of functionally identical antineutrino detectors immersed in pools of ultrapure water in three well-separated underground experimental halls near two nuclear reactor complexes. These pools serve both as shields against natural, low-energy radiation, and as water Cherenkov detectors that efficiently detect cosmic muons using arrays of photomultiplier tubes. Each pool is covered by a plane of resistive plate chambers as an additional means of detecting muons. Design, construction, operation, and performance of these muon detectors are described. (C) 2014 Elsevier By. All rights reserved.
人體通道傳輸方法以及系統
(2015-02-11)
桑梓賢
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周世傑
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張添烜
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孫致晴
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許碩文
一種人體通道傳輸方法包含以下步驟：使一第一人體通道傳輸裝置透過數種人體通道傳輸方式，分別傳送一測試訊號。藉由一第二人體通道傳輸裝置透過人體通道傳輸方式，分別接收測試訊號。根據透過各人體通道傳輸方式所接收之測試訊號，計算各人體通道傳輸方式之一訊噪比。選擇人體通道傳輸方式中，其訊噪比最大者。使第一人體通道傳輸裝置以及第二人體通道傳輸裝置間，以所選擇之人體通道傳輸方式傳輸資料。
電流刺激裝置
(2015-02-11)
林群祐
;
李易儒
;
柯明道
本發明提供一種電流刺激裝置，包括高壓輸出模組、電壓控制模組及電荷幫浦模組，高壓輸出模組係包含複數個電晶體且相疊接而成，用以接收控制電流刺激裝置之啟/閉之一輸入控制訊號及一第一電壓，第一電壓經疊加每一電晶體之輸出電壓後，據以轉換為一第二電壓並輸出予電壓控制模組，其根據第二電壓及一負載阻抗變化以輸出一電壓控制訊號，據以提供穩定之一刺激電流予負載，電荷幫浦模組根據電壓控制訊號以調整第一電壓之電壓值大小予高壓輸出模組，以適應性穩定刺激電流的輸出狀態。
可溶性二甲基矽氧烷修飾之聚（２－羥基乙基丙烯酸甲酯－甲基丙烯酸）雙性共聚物及其製備方法
(2015-02-11)
劉典謨
;
黃筠淳
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許仲育
本發明係揭露一種可溶性二甲基矽氧烷修飾之聚(2-羥基乙基丙烯酸甲酯-甲基丙烯酸)雙性共聚物及其製備方法，其係基於2-羥基乙基丙烯酸甲酯(HEMA)、甲基丙烯酸(MAA)和末端3-丙基胺聚二甲基矽氧烷(PDMS)以化學鍵結方式在水溶液中合成。此可溶性二甲基矽氧烷修飾之聚(2-羥基乙基丙烯酸甲酯-甲基丙烯酸)雙性共聚物更可完全溶於醇類溶劑，以利後續之加工需求，並具可調整之親疏水性及良好的生物相容性，故可應用於防沾附或藥物釋放等之應用。
Structural Evolution of Crystalline Conjugated Polymer/Fullerene Domains from Solution to the Solid State in the Presence and Absence of an Additive
(2015-02-12)
Su, Yu-Wei
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Liu, Chih-Ming
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Jiang, Jian-Ming
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Tsao, Cheng-Si
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Cha, Hou-Chin
The power conversion efficiencies of polymer/fullerene solar cells are critically dependent on the nanometer-scale morphologies of their active layers, which are typically processed from solution. Using synchrotron wide- and small-angle X-ray scattering, we have elucidated the intricate mechanism of the structural transitions from solutions to solid films of the crystalline polymer poly[bis(dodecyl)thiophene-thieno[3,4-c]pyrrole-4,6-dione] (PBTTPD) and [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM), including the effect of the solvent additive 1,6-diiodohexane (DIH). We found that the local assembly of rigid-rod PBTTPD segments that formed in solution instantly and then relaxed within several hundred seconds upon cooling to room temperature from 90 degrees C could re-emerge and develop into seeds for subsequent crystallization of the polymer in the solid films. At room temperature (25 degrees C), the presence of DIH in chlorobenzene slightly enhanced the formation of local assembly PBTTPD segments in the supersaturated PBTTPD in PBTTPD/PC71BM blend solution. Two cases of films were subsequently developed from these blend solutions with drop-casted and spin-coated methods. For spin-coated thin films (90 nm thick), which evolve quickly, polymers crystallinity and the fullerene packing in the solid-state thin films were enhanced in the case of involving DIH. Regarding the effect of DIH for processing the drop-casted thick films (2.5 mu m thick), which evolve slowly, DIH has no observable effect on PBTTPD/PC71BM structure. Our results provide some understanding of the mechanism behind the structural development of polymer/fullerene blends upon their transitions from solution to the solid state, as well as the key functions of the additive.
Chitosan-PEG Hydrogel with Sol-Gel Transition Triggerable by Multiple External Stimuli
(2015-02-12)
Tsao, Ching Ting
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Hsiao, Meng Hsuan
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Zhang, Mengying Y.
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Levengood, Sheeny Lan
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Zhang, Miqin
Smart hydrogels play an increasingly important role in biomedical applications, since materials that are both biocompatible and multi-stimuli-responsive are highly desirable. A simple, organic solvent-free method is presented to synthesize a biocompatible hydrogel that undergoes a sol-gel transition in response to multiple stimuli. Methoxy-poly(ethylene glycol) (mPEG) is modified into carboxylic-acid-terminated-methoxy-poly(ethylene glycol) (mPEG-acid), which is then grafted onto chitosan via amide linkages yielding mPEG-g-chitosan. Grafting of mPEG onto hydrophobic chitosan imparts hydrophilic properties to the resultant polymer. The mPEG-g-chitosan gel exhibits a controllable multi-stimuli-responsive property. The balance between hydrophilicity and hydrophobicity is believed to confer mPEG-g-chitosan with stimuli-responsive behavior. The effect of salt concentration, solute concentration, temperature, and pH on the sol-gel transition of mPEG-g-chitosan is evaluated and the underlying mechanisms of mPEG-g-chitosan polymer packing and gelation property is discussed.
Direct kinetic measurement of the reaction of the simplest Criegee intermediate with water vapor
(2015-02-13)
Chao, Wen
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Hsieh, Jun-Ting
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Chang, Chun-Hung
;
Lin, Jim Jr-Min
;
應用化學系
Carbonyl oxides, or Criegee intermediates, are important transient species formed in the reactions of unsaturated hydrocarbons with ozone. Although direct detection of Criegee intermediates has recently been realized, the main atmospheric sink of Criegee intermediates remains unclear. We report ultraviolet absorption spectroscopic measurements of the lifetime of the simplest Criegee intermediate, CH2OO, at various relative humidity levels up to 85% at 298 kelvin. An extremely fast decay rate of CH2OO was observed at high humidity. The observed quadratic dependence of the decay rate on water concentration implied a predominant reaction with water dimer. On the basis of the water dimer equilibrium constant, the effective rate coefficient of the CH2OO + (H2O)(2) reaction was determined to be 6.5 (+/-0.8) x 10(-12) cubic centimeters per second. This work would help modelers to better constrain the atmospheric concentrations of CH2OO.