Browsing by Author "Chen, KH"

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3-port polarization-independent optical quasi-circulator with holographic spatial walk-off polarizers
(2004)
Chen, JH
;
Chen, KH
;
Hsieh, PJ
;
Su, DC
;
光電工程學系
An alternative type of 3-port polarization-independent optical quasi-circulator by utilizing a pair of holographic spatial walk-off polarizers (HSWPs). is proposed. This device consists of a reflection Prism, three polarization beamsplitter cubes, a pair of HSWPs, a Faraday rotator, and a half-wave, plate. The operating principles, the characteristics, and the performances: of this device and HSWPs are discussed. In order to show the validity, the prototype device operating in 1300nm is assembled and tested, experimentally. The merits of this design include polarization-independence, compactness, high isolation, and easy fabrication. It should also be possible to design the device operating at 1550 nm wavelength range.
A method for measuring the complex refractive index and thickness of a thin metal film
(2003-12-01)
Chen, KH
;
Hsu, CC
;
Su, DC
;
光電工程學系
;
Department of Photonics
A circularly polarized heterodyne light beam is incident on a thin metal film, causing successive reflections and refractions to occur at the two sides of the thin film. The phase difference between p- and s-polarizations of the multiple-beam interference signal can be measured accurately with an analyzer and heterodyne interferometry. The phase difference depends on the azimuth angle of the analyzer, the complex refractive index and the thickness of the thin metal film. The measured values of the phase differences under three different azimuth angles of the analyzer can be substituted into the special equations derived from Fresnel's equations and multiple-beam interference. Hence, the complex refractive index and the thickness of the thin metal film can be estimated by using a personal computer with a numerical analysis technique. Because of its common-path optical configuration and its heterodyne interferometric phase measurement, this method has many merits, such as high stability against surrounding vibrations, high resolution and easy operation.
A method for measuring the concentration of a solution
(2003)
Su, DC
;
Chen, KH
;
Hsu, CC
;
交大名義發表
;
National Chiao Tung University
When a linearly polarized light beam enters a surface-plasmon-resonanse (SPR) apparatus and is incident on the boundary surface with tested solution at the resonant angle, the phase difference between s- and p- polarizations is changed with the concentration of the solution. And the phase difference can be measured accurately by the heterodyne interferometry. Based on these effects, a method for measuring the concentration of a solution is presented.
Alternative method for measuring both the refractive indices and the thickness of silver-halide holographic plates
(2005-05-01)
Hsu, CC
;
Lin, JY
;
Chen, KH
;
Su, DC
;
光電工程學系
First, the phase differences between s- and p-polarizations of a circularly polarized heterodyne light beam reflected from the emulsion layer, and that from its substrate, are measured, respectively. The measured data are substituted into specially derived equations, so the refractive indices of the emulsion layer and its substrate can be calculated. Second, the variations of phase differences between s- and p-polarizations due to the wavelength shifts and the extraction of the holographic plate in a modified Michelson interferometer are measured. Then, the thickness of the emulsion layer and its substrate can be estimated based on the measured values of refractive indices, the wavelength shifts, and the phase difference variations. This method has some advantages, such as high resolution and easy operation in only one optical configuration. (c) 2005 Society of Photo-Optical Instrumentation Engineers.
Bidirectional current-mode capacitor multiplier in DC-DC converter compensation
(2005)
Chang, CJ
;
Chen, KH
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Bidirectional current-mode capacitor multipliers for on-chip DC-DC converter compensation are presented in this paper. The increasing demand for portable devices is a driving force toward higher integration. Reducing physical area with the same or better performance is carried out. Based on TSMC 0.35 mu m technology, we demonstrate that a small capacitor is multiplied by a factor about 200. It allows the control system compensating circuit of DC-DC converter be easily integrated on a chip and occupy less silicon area. The experimental results show that the DC-DC converter with proposed architecture is stable for wide loading conditions from 10mA to 400mA while input voltage is 3.3 V and output voltage is 2.0V. The quiescent current consumed is 9 mu A by single-ended capacitor multiplier and 19 mu A by two-ended capacitor multiplier.
Comparative studies on field emission properties of carbon-based materials
(2000-04-01)
Chen, KH
;
Wu, JJ
;
Chen, LC
;
Wen, CY
;
Kichambare, PD
Comparative studies on field emission properties of various carbon-related materials including diamond, amorphous carbon, SiCN films, SiCN nanorods, and carbon nanotubes are presented. While diamond is well known for its potential use in cold cathodes, the emission current of a hydrogen-treated diamond film is relatively small compared to that of amorphous carbon or diamond-like-carbon film. Meanwhile, carbon nanotubes have demonstrated large emission currents at much lower threshold voltages, showing their potential for applications. However, the emission from carbon nanotubes is subjected to significant decay under long-term operation. The emission current and long-term stability can be improved using a new SiCN compound with nanorod morphology. The effective barrier height and the held enhancement factor derived from the Fowler-Nordheim equation are discussed in this paper. (C) 2000 Elsevier Science S.A. All rights reserved.
Comparison of the electronic structures of AIN nanotips grown on p- and n-type Si substrates
(2005-12-07)
Chiou, JW
;
Tsai, HM
;
Pao, CW
;
Dong, CL
;
Chang, CL
At and N K-edge x-ray absorption near-edge structure (XANES), scanning photoelectron microscopy (SPEM) and x-ray emission measurements were performed on AIN nanotips grown on p- and n-type Si substrates (p-AIN and n-AIN). Features and intensities in the Al and N K-edge XANES spectra of these AIN nanotips overall are similar. In contrast, the intensities of the valence-band SPEM spectra of p-AIN are apparently larger than those of n-AIN, which indicates that the valence-band density of states of p-AIN exceeds that of n-AIN. This result may be related to the observed enhancement of field-emission intensity of AIN nanotips grown on the p-type Si substrate.
Controlling steps during early stages of the aligned growth of carbon nanotubes using microwave plasma enhanced chemical vapor deposition
(2002-10-01)
Chen, LC
;
Wen, CY
;
Liang, CH
;
Hong, WK
;
Chen, KJ
Vertically aligned carbon nanotubes (CNTs) with controllable length and diameter fabricated by microwave plasma enhanced chemical vapor deposition (MPECVD) are of continuing interest for various applications. This paper describes the role of process gas composition as well as the pre-coating catalytic layer characteristics. It is observed that nucleation of CNTs was significantly enhanced by adding nitrogen in the MPECVD process, which also promoted formation of bamboo-like structures. The very first key step toward growth of aligned CNTs was the formation of high-density fine carbon onion encapsulated metal (COEM) particles under a hydrogen plasma. Direct microscopic investigation of their structural evolution during the very early stages revealed that elongation, necking, and splitting of the COEM particles occurred accompanying the growth of CNTs, such that one of the split portions rode on the top of the growing tube while the remaining one resided on the root. Our results suggest that CNTs grow via the "tip-growth" as well as "root-growth" mechanisms.
Crystalline SiCN: a hard material rivals to cubic BN
(1999-11-01)
Chen, LC
;
Chen, KH
;
Wei, SL
;
Kichambare, PD
;
Wu, JJ
Growth and mechanical properties of SiCN materials prepared by microwave plasma enhanced chemical vapor deposition (CVD) as well as electron cyclotron resonance plasma CVD are reported. Large (several tens of microns), well-faceted ternary SiCN crystals were grown by microwave plasma-enhanced chemical vapor deposition. whereas amorphous SiCN films were deposited by ECR-CVD. The ternary crystalline compound (C; Si)(x)N-y exhibits a hexagonal structure and consists of a network wherein the Si and C are substitutional elements. While the N content of the crystalline compound is about 50 at.%, the extent of Si substitution varies and can be as low as 10 at.%. The amorphous SIGN films contain only about 30 at.% N. Nano-indentation studies were employed to investigate the mechanical properties of the SiCN materials. From the load versus displacement curves. we estimated the hardness and the effective modulus of the SIGN crystals to be around 30 and 321.7 GPa, respectively. The corresponding values for the amorphous SiCN were around 22 and 164.4 GPa, respectively. These values are well above most reported values for CN films. (C) 1999 Elsevier Science S.A. All rights reserved.
Deposition of silicon carbon nitride films by ion beam sputtering
(1999-11-01)
Wu, JJ
;
Wu, CT
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Liao, YC
;
Lu, TR
;
Chen, LC
Silicon carbon nitride films have been successfully synthesized at a temperature below 100 degrees C from an adenine(C5N5H5)-silicon-mixed target sputtered by Ar ion beam. The effects of Ar ion sputtering voltage, area ratio of Si to adenine in the mixed target and nitrogen atom addition during deposition on the film growth are investigated. XPS, XRD, and ellipsometry were employed to characterize the composition, chemical bonding, structure, and optical property of the films. The growth characteristic and film properties of the silicon carbon nitride films are also compared with those of the carbon nitride films deposited from an adenine target to elucidate the effect of silicon incorporation. The silicon content of the resultant films increased significantly as the area ratio of Si to adenine increased, whereas a higher Ar ion voltage led to a lower level of silicon incorporation, presumably due to differential sputtering yield of Si and adenine. XPS chemical stare analysis revealed multiple bonding structures for every element in the SiCN films, of which possible implications are given. XRD studies showed that only amorphous films for Si-rich SiCN were obtained, while the films with low Si incorporation and deposited at high Ar ion beam voltage contained nanocrystallites. Furthermore, the: refractive index of the SiCN films increased with increasing silicon content. The appearance of the nanocrystalline structure in the films led to a reduction in the refractive index. (C) 1999 Elsevier Science S.A. All rights reserved.
Effect of target materials on crystalline carbon nitride film preparation by ion beam sputtering
(1999-08-01)
Kuo, CT
;
Chen, LC
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Chen, KH
;
Chen, TM
;
Lu, TR
In order to provide abundant chemical information, two novel bio-molecular target materials, instead of the conventional graphite target, were successfully developed to determine the possible formation mechanisms of carbon nitride during ion beam deposition. The azaadenine and adenine targets consist of carbonitro bonding, high N/C ratio as well as a six-fold carbonitro ring structure similar to that in hypothetical C3N4. Mass spectroscopy was used to determine the possible mechanisms of these two target materials. A lower electron beam energy at 75 eV was adopted to generate as abundant fragmental ions during the decomposition of these targets. Mass spectroscopy study on these two different targets indicates that the adenine target exhibits a more complex decomposition mechanism than the azaadenine target. However, the seven common hydrogenated carbonitro-species may suggest the same predominant mechanism during the decomposition of these two targets under the present deposition condition. The good correlation is one reason why two different targets can make almost the same quality crystalline carbon nitride films, including bonding, composition and structure. (C) 1999 Elsevier Science S.A. All rights reserved.
Effects of high-density oxygen plasma posttreatment on field emission properties of carbon nanotube field-emission displays
(2005-11-01)
Juan, CP
;
Tsai, CC
;
Chen, KH
;
Chen, LC
;
Cheng, HGC
The effects of oxygen plasma posttreatment (PPT) on the morphology and field emission properties of carbon nanotube (CNT) arrays grown on silicon substrates are proposed and experimental results are reported. Oxygen PPT led to an enhancement in the emission properties of CNTs, which showed an increase in total emission current density and a decrease in turn-on field after plasma treatment. Scanning electron microscopy (SEM) images showed reduced densities of the CNTs, which resulted in a decrease of the screening effect in the electric field. Raman spectra showed an increase in the number of defects which served as field-emission sites when the plasma power or treatment time with the plasma increased. Transmission electron microscopy (TEM) images were used to identify the quality of the nanotubes, so that we could clearly find evidences of improvement in the field emission properties after plasma treatment. The measurement of electrical characteristics revealed improved field emission properties under proper plasma conditions. The turn-on field decreased from 4.8 to 2.5 V/mu m, and the emission current density increased from 78.7 mu A/cm(2) to 18 mA/cm(2) at an applied field of 5.5 V/mu m.
Electromigration in eutectic SnPb solder bumps with Ni/Cu UBM
(2005)
Chiu, SH
;
Liang, SW
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Chen, C
;
Lin, SS
;
Chou, CM
This study investigates the electromigration behavior of eutectic SnPb solder bumps with Ni/Cu UBM, in which the thickness of the Ni and Cu layer is 3 pm and 5 pm, respectively. It was found that the SnPb solderjoints have better electromigration resistance than that of SnAg bumps with thin film UBM. The thermal characteristic of SnPb solder joints under current stressing was measured by infrared technique. The Joule heating effect was less serious due to the wide Al trace of 100 mu m. Besides, a three-dimensional simulation on current density distribution was performed to examine the current crowding behavior in the joint. The results show that the current crowding occurs at the entrance point of the Al trace, which caused higher formation rate of intermetallic compounds there, and thus open failure occurred.
Enhancement in field emission of silicon microtips by bias-assisted carburization
(2000-11-01)
Kichambare, PD
;
Tarntair, FG
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Chen, LC
;
Chen, KH
;
Cheng, HC
Ultrathin carbon layers with thicknesses below 50 Angstrom have been deposited on silicon microtip arrays by bias-assisted carburization (BAC) using microwave plasma chemical vapor deposition. The tip radius of these silicon tips is reduced below 55 nm under low deposition temperature. The field emission characterization has been performed in a high-vacuum environment. An enhancement in the field emission is observed of about 3 orders of magnitude in BAC silicon microtips over untreated silicon microtips. With an applied voltage of 1100 V, emission currents of 80 and 120 muA have been achieved for the films grown (at de bias of -200 V for 40 min) with 15% and 25% CH4/H-2 gas ratio, respectively. An emission current of 40 muA has been achieved for the film grown (at de bias of -300 V for 30 min) with 3.5% CH4/H-2 ratio. The BAC silicon emitter has good emission stability at a constant voltage of 1100 V. These investigations indicate that further improvement of this technology will lead to simple and inexpensive field emission display devices. (C) 2000 American Vacuum Society. [S0734-211X(00)10706-1].
Experimental realization of breaking diffraction limit by planar negative-index metamaterials in free space
(2005-02-01)
Lih, JS
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Wang, YS
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Lu, MC
;
Huang, YC
;
Chen, KH
The sharpness of the image formed by a conventional lens is always limited by the wavelength of light. Recently, Pendry proposed a superlens, with a negative refractive index. such that the resolution is not limited by wavelength. Herein, we report direct experimental evidence of Pendry's superlens breaking the diffraction limit, in the microwave range of the X band (8-12 GHz), with a periodic array of split ring resonators and continuous wires; i.e. a meta-material with negative index of refraction.
Fabrication and characterization of carbon nanotube triodes
(2001-05-01)
Hong, WK
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Chen, KH
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Chen, LC
;
Tarntair, FG
;
Chen, KJ
To achieve high emission current density, carbon nanotube triodes have been proposed using recessed oxide as the insulator between the gate and the carbon nanotubes to replace the conventional spacer. An anode current of 10 muA was achieved with a gate voltage of 98 V for a nanotube sample prepared with a growth time of 12 min. Carbon nanotubes synthesized with various growth times were analyzed using a scanning electron microscope and Raman spectroscopy. By increasing the growth time, longer carbon nanotubes were obtained. Effects of the length of the carbon nanotubes on the field emission of the triodes are discussed, Enhanced luminance was obtained as the anode voltage increased from 600V to 1000V. Such carbon nanotube triodes are promising for utilization in future field-emission displays.
Fabrication and characterization of lateral field emission device based on carbon nanotubes
(2003)
Tsai, CC
;
Juan, CP
;
Chen, KJ
;
Chen, KH
;
Chen, LC
Fabrication and characterization of lateral field emission device based on carbon nanotubes
(2005-04-01)
Juan, CP
;
Tsai, CC
;
Chen, KH
;
Chen, LC
;
Cheng, HC
We have proposed and fabricated a vertical lateral field emission device (LFED) based on carbon nanotubes (CNTs). It combines high-performance nanomaterials with mature solid-state fabrication technology to produce miniaturized vacuum devices with superior field emission characteristics. The techniques employed are very simple and allow for good reproducibility in controlling the short distance from the polysilicon anode to the CNTs cathode inter-electrode distance. The inter-electrode gap can be easily fabricated to be less than 1 mu m by a wet etching process without using fine lithography. The CNTs were selectively grown using a microwave-plasma enhanced chemical vapor deposition system (MPCVD). The anode-to-emitter gap distance and the length of carbon nanotubes are well controlled to enable investigation of their effect on the field emission properties. The turn-on voltage of the fabricated device with an inter-electrode gap of 0.53 mu m is as low as 0.2V, and the emission current is as high as 9.72mA at 10V. The emission current fluctuation is approximately +/- 3.5% for 1500s.
Fabrication and characterization of low turn-on voltage carbon nanotube field emission triodes
(2001-08-01)
Cheng, HC
;
Chen, KJ
;
Hong, WK
;
Tantair, FG
;
Lin, CP
Based on selective growth, carbon nanotubes (CNTs) for low turn-on voltage field emission triodes have been grown via microwave plasma-enhanced chemical vapor deposition. The triode devices fabricated with standard integrated circuit process contain 4 x 4 emitting cells with extraction gates and each individual cell is 4 mum in diameter. With the phosphor-coated indium tin oxide glass as the anode away from the CNTs triodes with similar to1 mm above, the triode devices achieved low turn-on gate voltage of 30 V and high emission current density of 0.7 A/cm(2) at 50 V. The results exhibit CNTs for potential application in field emission display. (C) 2001 The Electrochemical Society.
Far-infrared resonance in split ping resonators
(2004-02-01)
Hsu, AC
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Cheng, YK
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Chen, KH
;
Chern, JL
;
Wu, SC
We experimentally investigated the resonance effect of planar metallic split ring resonators (SRRs) in the far-infrared region (FIR) (similar to10.6 mum). Experimental results indicated that they exhibit resonance around 10.6 mum, implying negative permeability in the FIR region. Furthermore, the ratio of effective dimensions of the SRR cell and the wavelength of the incident beam was around I which suggested a wide scale independence. This size tolerance is useful in realizing the meta-materials with negative indices of refraction in the optical wavelength domain.