Browsing by Author "Chen, Yen-Chun"

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All-Color Plasmonic Nanolasers with Ultralow Thresholds: Autotuning Mechanism for Single-Mode Lasing
(2014-08-01)
Lu, Yu-Jung
;
Wang, Chun-Yuan
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Kim, Jisun
;
Chen, Hung-Ying
;
Lu, Ming-Yen
We report on the first demonstration of broadband tunable, single-mode plasmonic nanolasers (spasers) emitting in the full visible spectrum. These nanolasers are based on a single metal oxide semiconductor nanostructure platform comprising of InGaN/GaN semiconductor nanorods supported on an Al2O3-capped epitaxial Ag film. In particular, all-color lasing in subdiffraction plasmonic resonators is achieved via a novel mechanism based on a property of weak size dependence inherent in spasers. Moreover, we have successfully reduced the continuous-wave (CW) lasing thresholds to ultrasmall values for all three primary colors and have clearly demonstrated the possibility of "thresholdless" lasing for the blue plasmonic nanolaser.
All-Color Plasmonic Nanolasers with Ultralow Thresholds: Autotuning Mechanism for Single-Mode Lasing
(2014-08-01)
Lu, Yu-Jung
;
Wang, Chun-Yuan
;
Kim, Jisun
;
Chen, Hung-Ying
;
Lu, Ming-Yen
We report on the first demonstration of broadband tunable, single-mode plasmonic nanolasers (spasers) emitting in the full visible spectrum. These nanolasers are based on a single metal oxide semiconductor nanostructure platform comprising of InGaN/GaN semiconductor nanorods supported on an Al2O3-capped epitaxial Ag film. In particular, all-color lasing in subdiffraction plasmonic resonators is achieved via a novel mechanism based on a property of weak size dependence inherent in spasers. Moreover, we have successfully reduced the continuous-wave (CW) lasing thresholds to ultrasmall values for all three primary colors and have clearly demonstrated the possibility of "thresholdless" lasing for the blue plasmonic nanolaser.
Antibacterial gold nanoparticle-based photothermal killing of vancomycin-resistant bacteria
(2018-06-01)
Wang, Sin-Ge
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Chen, Yen-Chun
;
Chen, Yu-Chie
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應用化學系
;
Department of Applied Chemistry
Aim: The extensive use of vancomycin has given rise to vancomycin-resistant bacterial strains, such as vancomycin-resistant Enterococci (VRE). We aim to explore potent medical treatments that can inhibit the growth of VRE. Materials & methods: Vancomycin-immobilized gold nanoparticles (Au@Van NPs) with polygonal shapes from one-pot reactions were generated within approximately 7 min. Results & discussion: The as-prepared Au NPs exhibit not only antibacterial capability but also photothermal competence. The temperature of the sample solution containing the as-prepared Au@Van NPs can be raised by approximately 15 degrees C under irradiation by a near-infrared laser (lambda = 808 nm) within 5 min. Conclusion: The required amount of vancomycin on the as-prepared Au@Van NPs combined with near-infrared irradiation for inhibiting VRE is approximately 16-fold lower than that of free-form vancomycin.
Carbon Fiber Ionization Mass Spectrometry for the Analysis of Analytes in Vapor, Liquid, and Solid Phases
(2017-12-19)
Wu, Min-Li
;
Chen, Te-Yu
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Chen, Yen-Chun
;
Chen, Yu-Chie
;
應用化學系
Various ionization methods in mass spectrometry (MS) are available for the analysis of analytes with different properties. Nonetheless, the use of a single ionization method to analyze mixtures containing analytes with different polarities and volatilities in different phases at atmospheric pressure remains a challenge. Exploring an ionization method that can ionize small organics and large biomolecules with different properties for MS analysis is advantageous. Carbon fiber ionization mass spectrometry (CFI-MS), which uses a carbon fiber bundle as the ion source, is useful for the analysis of small organics with low polarities. Voltage needs to be applied on the carbon fiber bundle to initiate corona discharge for ionization of analytes. In this study, we explore the suitability of using CFI-MS in the analysis of analytes in vapor, liquid, and solid phases using a single carbon fiber (length : similar to 1 cm; diameter: similar to 10 mu m) as the ion source. Furthermore direct electric contact on the carbon fiber is not required. We demonstrate that CFI-MS is useful for analyzing not only small and low-polarity organics but also polar biomolecules, such as peptides and proteins. The limits of detection for analytes with high polarities such as dodecyl trimethylammonium bromide and bradykinin are estimated to be similar to 16 and similar to 53 pM, respectively. Ionization mechanisms, including corona discharge and electrospray, are involved in the ionization of analytes with the polarity from low to high. Furthermore, sesame oil containing aromatic volatiles and compounds with different polarities is used as a model sample to demonstrate the capability of the developed ionization method to provide comprehensive chemical information from a complex sample. In addition, the feasibility of using the developed method for quantitative analysis of nonpolar as well as medium and high polarity analytes is also demonstrated. The sensitivity of the developed method toward analytes with high polarity is higher than those with low polarity. The method precision was estimated to be similar to 7.8%.
Design of multifold Ge/Si/Ge composite quantum-dot heterostructures for visible to near-infrared photodetection
(2015-05-15)
Kuo, Ming-Hao
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Lai, Wei-Ting
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Lee, Sheng-Wei
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Chen, Yen-Chun
;
Chang, Chia-Wei
We demonstrate an effective approach to grow high-quality thin film (>1 mu m) ofmultifold Ge/Si/Ge composite quantum dots ( CQDs) stacked heterostructures for near infrared photodetection and optical interconnect applications. An otherwise random, self-assembly of variable-fold Ge/Si CQDs has been grown on Si through the insertion of Si spacer layers to produce micron-scale-thick, stacked Ge/Si CQD layers with desired QD morphology and composition distribution. The high crystalline quality of these multifold Ge CQD heterostructures is evidenced by low dark current density of 3.68 pA/mu m(2), superior photoresponsivity of 267 and 220 mA/W under 850 and 980 nm illumination, respectively, and very fast temporal response time of 0.24 ns measured on the Ge/Si CQD photodetectors. (C) 2015 Optical Society of America
Direct large-area growth of graphene on silicon for potential ultra-low-friction applications and silicon-based technologies
(2020-08-14)
Tseng, Wei-Shiuan
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Chen, Yen-Chun
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Hsu, Chen-Chih
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Lu, Chen-Hsuan
;
Wu, Chih-, I
Deposition of layers of graphene on silicon has the potential for a wide range of optoelectronic and mechanical applications. However, direct growth of graphene on silicon has been difficult due to the inert, oxidized silicon surfaces. Transferring graphene from metallic growth substrates to silicon is not a good solution either, because most transfer methods involve multiple steps that often lead to polymer residues or degradation of sample quality. Here we report a single-step method for large-area direct growth of continuous horizontal graphene sheets and vertical graphene nano-walls on silicon substrates by plasma-enhanced chemical vapor deposition (PECVD) without active heating. Comprehensive studies utilizing Raman spectroscopy, x-ray/ultraviolet photoelectron spectroscopy (XPS/UPS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical transmission are carried out to characterize the quality and properties of these samples. Data gathered by the residual gas analyzer (RGA) during the growth process further provide information about the synthesis mechanism. Additionally, ultra-low friction (with a frictional coefficient similar to 0.015) on multilayer graphene-covered silicon surface is achieved, which is approaching the superlubricity limit (for frictional coefficients <0.01). Our growth method therefore opens up a new pathway towards scalable and direct integration of graphene into silicon technology for potential applications ranging from structural superlubricity to nanoelectronics, optoelectronics, and even the next-generation lithium-ion batteries.
Distributed Bragg Reflectors as Broadband and Large-Area Platforms for Light-Coupling Enhancement in 2D Transition-Metal Dichalcogenides
(2018-05-16)
Chen, Yen-Chun
;
Yeh, Han
;
Lee, Chien-Ju
;
Chang, Wen-Hao
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電子物理學系
Two-dimensional (2D) semiconductors, particularly the direct-gap monolayer transition metal dichalcogenides (TMDs), are currently being developed for various atomically thin optoelectronic devices. However, practical applications are hindered by their low quantum efficiencies in light emissions and absorptions. While photonic cavities and metallic plasmonic structures can significantly enhance the light-matter interactions in TMDs, the narrow spectral resonance and the local hot spots considerably limit the applications when broadband and large area are required. Here, we demonstrate that a properly designed distributed Bragg reflector (DBR) can be an ideal platform for light-coupling enhancement in 2D TMDs. The main idea is based on engineering the amplitude and phase of optical reflection from the DBR to produce optimal substrate-induced interference. We show that the TMDs photoluminescence, Raman, and second harmonic generation signals of monolayer WSe2 can be enhanced by a factor of 26, 34, and 58, respectively. The proposed DBR substrates pave the way for developing a range of 2D optoelectronic devices for broadband and large-area applications.
Efficient modulation of subwavelength focusing via meta-aperture-based plasmonic lens for multifunction applications
(2018-09-11)
Chang, Kai-Hao
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Chen, Yen-Chun
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Chang, Wen-Hao
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Lee, Po-Tsung
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電子物理學系
Subwavelength focusing is crucial for many applications in photonics including super-resolution micro/nanoscopy, nanolithography, and optical trapping. However, most nanostructures exhibit poor ability to modulate focusing spot, which makes them hard to achieve ultra-small resolution. Here, we propose three kinds of plasmonic lens (PL) by utilizing different meta-aperture designs for efficient subwavelength focusing modulation. The shape of nanoaperture strongly influences the diffraction properties. Spatial modulation of focusing spot by employing a circular array of proposed nanoapertures is explored. The best focusing performance among these PLs is the design of T-shape nanoaperture, which has great resolution achieving ultra-small focusing spot of 0.14.2 and 0.20.2 (lambda = 633 nm) for simulation and experiment respectively, better than lots of focusing devices especially by using linear polarization. Multiple-object trapping can be realized by using T-shape nanoaperture-based PL. Our designed PLs with different nanoapertures demonstrate the capability to broaden and integrate different functionalities for on-chip nanotechnologies development.
Efficient single photon sources based on nanodiamonds on a plasmonic platform
(2014)
Chen, Yen-Chun
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Tsai, Cheng-Yen
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Wang, Chun-Yuan
;
Gwo, Shangir
;
Wen-HaoChang
We report on an efficient room-temperature source of single photons based on single nitrogen-vacancy centers in nanodiamonds (NDs) placing on a large-area plasmonic platform formed by crystalline gold flakes covered with a thin dielectric layer. Due to the strongly confined plasmonic fields in the thin dielectric layer, the NDs show a large enhancement in the fluorescence intensity without significant degradation in single photon purity. According to the deduced fluorescence lifetime from g((2)) measurements, the Purcell factor is estimated to be similar to 1.4. The plasmonic platform is very ideal for large-area fluorescence enhancement without the needs of sophisticated nanopositioning schemes for locating NDs at local hot spots in conventional plasmonic nanostructures.
Fabricating GaN-based LEDs on (-201) beta-Ga2O3 substrate via non-continuous/continuous growth between low-temperature undoped-GaN and high-temperature undoped-GaN in atmospheric pressure metal-organic chemical vapor deposition
(2019-10-01)
Lan, Yu-Pin
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Chen, Yen-Chun
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Yeh, Yi-Yun
;
Hung, Shun-Ming
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光電系統研究所
This study demonstrates two approaches to the growth of GaN-based LEDs on (-2 0 1)-oriented beta-Ga2O3 single crystal substrates using metalorganic CVD under atmospheric pressure. One approach induces non-continuous growth between low-temperature undoped-GaN (u-GaN) and high-temperature u-GaN, whereas the other approach induces continuous growth. We observed the following reduction in the FWHM of X-ray diffraction rocking curves: GaN (0 0 2) on (-2 0 1) beta-Ga2O3 substrate (from 464 to 342 arcsec) and GaN (1 0 2) (from 886 to 493 arcsec). An LED with six pairs of InGaN/GaN multiple quantum wells was successfully fabricated on the (-2 0 1) beta-Ga2O3 single crystal substrate. (C) 2019 The Japan Society of Applied Physics
Femtosecond-Laser Ablation of Monolayer Tungsten Diselenide (WSe2) on Sapphire
(2018-01-01)
Chen, Yu-Ling
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Tseng, Ya-Hsin
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Chen, Yen-Chun
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Chang, Wen-Hao
;
Her, Tsing-Hua
Near-IR femtosecond laser ablation of monolayer tungsten diselenide WSe2 on sapphire is demonstrated. The ablation threshold is found low (below 10 mJ/cm(2)), due to its low dimensionality and weak coupling to substrates. Substrate-dependent ablation threshold is predicted and will be discussed.
Investigation of the spectral characteristics of silicon-vacancy centers in ultrananocrystalline diamond nanostructures and single crystalline diamond
(2020-01-21)
Kunuku, Srinivasu
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Chen, Yen-Chun
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Chen, Chien-Hsu
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Kandasami, Asokan
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Chang, Wen-Hao
Silicon-vacancy (SiV) centers were produced in single crystalline diamond (SCD) and ultrananocrystalline diamond (UNCD) nanostructures via Si ion implantation or in situ Si doping. SiV-embedded UNCD (SiV-UNCD) was fabricated by both top-down and bottom-up methods. The spectral properties of the SiV centers, including the zero phonon line (ZPL) width and decay time, were investigated in the SCD and UNCD nanostructures. All the SiV-UNCD nanostructures showed bright emission regardless of the preparation method. However, the decay time of the SiV centers was affected by the synthesis procedure. A SiV decay time of tau similar to 0.19 ns was observed for UNCD nanostructures formed by in situ doping, whereas the SiV decay time was similar to 0.43 ns for SiV-UNCD clusters prepared by Si ion implantation into UNCD deposited on Ti/sapphire substrates. The ultrasonication of UNCD clusters on Ti/sapphire pyramids produced bright SiV-UNCD nanoclusters with sizes of similar to 50 nm, a ZPL width of 13.5 nm, and a decay time of 0.35 ns, suggesting promising potential in bioimaging applications. SiV-containing SCD (type Ia or type IIa) showed enhanced SiV spectral properties with a ZPL width of 6.08 nm and longer decay time of 1.3 ns. Published under license by AIP Publishing.
Low-Threshold Plasmonic Lasers on a Single-Crystalline Epitaxial Silver Platform at Telecom Wavelength
(2017-06-01)
Lee, Chien-Ju
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Yeh, Han
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Cheng, Fei
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Su, Ping-Hsiang
;
Her, Tsing-Hua
We report on the first demonstration of metal insulator semiconductor-type plasmonic lasers at the telecom wavelength (similar to 1.3 mu m) using top-down fabricated semiconductor waveguides on single-crystalline metallic platforms formed using epitaxially grown Ag films. The critical role of the Ag film thickness in sustaining. plasmonic lasing at the telecom wavelength is investigated systematically. Low-threshold (0.2 MW/cm(2)) and continuous-wave operation of plasmonic lasing at cryogenic temperatures can be achieved on a 150 nm Ag platform with minimum radiation leakage into the substrate. Plasmonic lasing occurs preferentially through higher-order surface-plasmon-polariton modes, which exhibit a higher mode confinement factor, lower propagation loss, and better field gain coupling. We observed plasmonic lasing up to 200 K under pulsed excitations. The plasmonic lasers on large-area epitaxial Ag films open up a scalable platform for on-chip integrations of plasmonics and optoelectronics at the telecom wavelength.
Magnetic hyperthermia enhance the treatment efficacy of peri-implant osteomyelitis
(2017-07-25)
Fang, Chih-Hsiang
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Tsai, Pei-I
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Huang, Shu-Wei
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Sun, Jui-Sheng
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Chang, Jenny Zwei-Chieng
Background: When bacteria colony persist within a biofilm, suitable drugs are not yet available for the eradication of biofilm-producing bacteria. The aim of this study is to study the effect of magnetic nano-particles-induced hyperthermia on destroying biofilm and promoting bactericidal effects of antibiotics in the treatment of osteomyelitis. Methods: Sixty 12-weeks-old male Wistar rats were used. A metallic 18G needle was implanted into the bone marrow cavity of distal femur after the injection of Methicillin-sensitive Staphylococcus aureus (MSSA). All animals were divided into 5 different treatment modalities. The microbiological evaluation, scanning electron microscope examination, radiographic examination and then micro-CT evaluation of peri-implant bone resorption were analyzed. Results: The pathomorphological characteristics of biofilm formation were completed after 40-days induction of osteomyelitis. The inserted implants can be heated upto 75 degrees C by magnetic heating without any significant thermal damage on the surrounding tissue. We also demonstrated that systemic administration of vancomycin [VC (i.m.)] could not eradicate the bacteria; but, local administration of vancomycin into the femoral canal and the presence of magnetic nanoparticles hyperthermia did enhance the eradication of bacteria in a biofilm-based colony. In these two groups, the percent bone volume (BV/TV: %) was significantly higher than that of the positive control. Conclusions: For the treatment of chronic osteomyelitis, we developed a new modality to improve antibiotic efficacy; the protection effect of biofilms on bacteria could be destroyed by magnetic nanoparticles-induced hyperthermia and therapeutic effect of systemic antibiotics could be enhanced.
Original method of GaN and InGaN quantum dots formation on (0001)AlN surface by ammonia molecular beam epitaxy
(2017-01-01)
Zhuravlev, K. S.
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Gulyaev, D. V.
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Aleksandrov, I. A.
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Malin, T. V.
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Mansurov, V. G.
We report original method of formation Ga(In)N/AlN quantum dots with low density by ammonia MBE on the (0001)AlN surface by using a decomposition process of Ga(In)N thin layer. Low density of quantum dots have been obtained in the range 10(7)-10(9) cm(-2). Single quantum dots photoluminescence lines corresponding to exciton and biexciton transitions were observed in micro-photoluminescence spectra.
Plasmonic whispering-gallery modes in a semiconductor-insulator-metal hybrid structure
(2015)
Lee, Chien-Ju
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Yeh, Han
;
Chen, Yen-Chun
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Wang, Chun-Yuan
;
Gwo, Shangir
We demonstrate a plasmonic cavity based on a hybrid semiconductor-insulator-metal structure, which can support plasmonic whispering-gallery modes (WGMs) in the insulator layer. The hybrid structure consists of a semiconductor microdisk with embedded gain medium on top of a single-crystalline gold flake with a nanometer-thick dielectric gap in between. By optimizing the dielectric gap thickness, it is possible to form coupled modes consisting of both photonic WGM in the microdisk and plasmonic WGM in the dielectric gap, by which a high field-gain overlap and an efficient cavity feedback can be achieved for investigating strong light-matter interactions and laser applications.
Synthesis of SiV-diamond particulates via the microwave plasma chemical deposition of ultrananocrystalline diamond on soda-lime glass fibers
(2016-10-01)
Kunuku, Srinivasu
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Chen, Yen-Chun
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Yeh, Chien-Jui
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Chang, Wen-Hao
;
Manoharan, Divinah
Wereport the synthesis of silicon-vacancy (SiV) incorporated spherical shaped ultrananocrystalline diamond (SiV-UNCD) particulates (size similar to 1 mu m) with bright luminescence at 738 nm. For this purpose, different granular structured polycrystalline diamond films and particulates were synthesized by using three different kinds of growth plasma conditions on the three types of substrate materials in the microwave plasma enhanced CVD process. The grain size dependent photoluminescence properties of nitrogen vacancy (NV) and SiV color centers have been investigated for different granular structured diamond samples. The luminescence of NV center and the associated phonon sidebands, which are usually observed in microcrystalline diamond and nanocrystalline diamond films, were effectively suppressed in UNCD films and UNCD particulates. Micron sized SiV-UNCD particulates with bright SiV emission has been attained by transfer of SiV-UNCD clusters on soda-lime glass fibers to inverted pyramidal cavities fabricated on Si substrates by the simple crushing of UNCD/soda-lime glass fibers in deionized water and ultrasonication. Such a plasma enhanced CVD process for synthesizing SiV-UNCD particulates with suppressed NV emission is simple and robust to attain the bright SiV-UNCD particulates to employ in practical applications.
Three-Dimensional Resolvable Plasmonic Concentric Compound Lens: Approaching the Axial Resolution from Microscale to Nanoscale
(2018-03-01)
Chang, Kai-Hao
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Chen, Yen-Chun
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Chang, Wen-Hao
;
Lee, Po-Tsung
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電機學院
We propose the design and working principle of a plasmonic concentric compound lens (CCL) comprising inner circular nanoslits and outer circular nanogrooves. Dual-wavelength operations have been achieved for 650 and 750 nm at nanoscale and microscale focal lengths along with their depth of focus (DOF). By tuning the arrangement of nanogrooves, the axial resolution can be modulated and the narrowest DOF is achieved by a design of gradually decreasing groove width. For the ultrahigh tunability of axial resolution, DOF over 400 nm for both working wavelengths is also achieved. We not only developed an approximate-perturbed-focus model for explaining the performance of DOF but also found an extraordinary way to improve the resolution. The enhanced resonance of central disk as nannoantenna in CCL also has great influence on nanofocusing with different deigns of outer nanogrooves. This work provides new sight of focusing ability governed by the general optical nanogrooves. The optimized CCL shows excellent focusing performance with a lateral resolution down to 0.32 lambda (lambda= 650 nm), which is the best resolving ability achieved thus far in the near field region with a long focal length up to 500 nm.