Browsing by Author "Wu, CT"

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An electro-thermally driven microactuator with two dimensional motion
(2002-03-01)
Wu, CT
;
Hsu, W
;
機械工程學系
;
Department of Mechanical Engineering
In previous literatures, most of the microactuators were designed to deflect in one dimension only. Here, an electro-thermally driven microactuator with out-of-plane and in-plane two dimensional motion is designed, fabricated and tested. This microactuator comprised of a series of bimorph beams, a moving plate, a lateral driven unit, and contact pads. The out-of-plane motion is produced due to the bimorph effect and residual stress between the layers of Au and polysilicon when they are heated. The in-plane motion is obtained by heating the lateral driven unit which consists of two adjacent beams with different cross sections but the same length, then the asymmetrical thermal expansions in two adjacent beams lead to lateral deflection. The microactuator proposed here is fabricated by surface micromaching technique. A twostep releasing method is used here to free the microactuator successfully. The testing results show that the lateral driven unit can produce 10 mum lateral displacements at input voltages of 5 V, and bimorph structures at the same voltage can produce about 12 mum downward displacement. It is also found that this two dimensional motion can be controlled almost independently.
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.
Deposition of silicon carbon nitride films by ion beam sputtering
(1999-11-01)
Wu, JJ
;
Wu, CT
;
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.
Design and fabrication of a three-dimensional long-stretch micro drive by electroplating
(2003)
Wu, CT
;
Tai, WC
;
Hsu, CP
;
Hsu, W
;
機械工程學系
Although lots of works have been devoted to develop the microactuators or microstructures, few researches have been done on three-dimensional microactuators. Here the feasibility investigation on a three-dimensional electrothermally driven long-stretch micro drive (LSMD) is proposed by integrating the LSMD and mechanical hinge mechanism. The LSMD (about 2000 mum x 500 mum) consists of two cascaded compliant structures in parallel. Each cascaded structure is formed by connecting several basic actuation units in series. The mechanical hinge is used to allow the LSMD to be lifted as a three-dimensional structure. One of the important issues in fabricating the three-dimensional microactuator is the conducting circuit to actuate the microactuator. Here the Ni electroplating process is used to fabricate the mechanical hinge structure and the LSMD, then the mechanical hinge itself can act as the conductive circuit easily. From the LSMD simulation results, several design parameters are found to have significant influence on the output displacements. Larger out-stretching displacements are feasible by proper choice of design parameters. Preliminary fabrication results of nickel-made LSMD exhibit output displacement of 190 mum at input voltage of 3 volts. Fabrication results of nickel-made three-dimensional LSMD are also presented.
Design and fabrication of an electrothermal microactuator for multi-level conveying
(2006-03-01)
Wu, CT
;
Hsu, WY
;
機械工程學系
;
Department of Mechanical Engineering
During the past years, a variety of microactuators developed for micro-conveyors have been presented. However, such micro-conveyors can only provide conveying motion in a single plane. Here an electrothermally driven microactuator with a capability of adjustable height is proposed, which may act as a basic unit for multi-level conveyors. This microactuator is based on the principle of thermal bimorph actuation with two long conveying fingers to exert out-of-plane bending motions in the transversal direction, which are connected and lifted by an initially curved height adjuster in the longitudinal direction. The devices can provide conveyance of micro-objects between two plane levels of different heights. The testing results show that the two fingers and a height adjuster can be actuated simultaneously and individually with little thermal crosstalk. The proposed device with a dimension of 900x100x4.5 mu m(3) can provide 5 mu m vertical displacements by the height adjuster at 1 V and 18 mu m lateral displacements by the conveying finger at 2 V. Simulations by finite-element program ANSYS 5.7 have been performed and widely match with testing results.
Generally applicable self-masked dry etching technique for nanotip array fabrication
(2004-03-01)
Hsu, CH
;
Lo, HC
;
Chen, CF
;
Wu, CT
;
Hwang, JS
Well-aligned nanotip arrays were fabricated by electron cyclotron resonance (ECR) plasma process using gas mixtures of silane, methane, argon, and hydrogen. The resultant tips have nanoscale apexes (similar to1 nm) with high aspect ratios (similar to50), which were achieved by simultaneous SiC nanomask formation and dry etching during ECR plasma process. This technique was applied to a variety of substrates such as silicon, polycrystalline silicon, gallium nitride, gallium phosphide, sapphire, and aluminum, indicating its general applicability. High-resolutiontransmission electron microscopy and Auger depth profile analyses revealed that the SiC cap, with Si:C ratio of 1:1, exhibited 3C-SiC and 2H-SiC structure on Si and GaP, respectively, with heteroepitaxial relationship. This one-step self-masked dry etching technique enables the fabrication of uniform nanotip arrays on various substrates over large area at low process temperatures, thereby demonstrating a high potential for practical industrial application.
Local displacement measurement and physical modeling
(2003)
Huang, AB
;
Wu, CT
;
Hsu, HH
;
土木工程學系
;
Department of Civil Engineering
The importance and value of local displacement measurement in physical modeling and/or field tests have been well recognized. This paper describes two cases where local displacement was monitored for cone penetration tests (CPT) in a calibration chamber and model foundation load tests. In the CPT chamber calibration tests, local displacement measurement was used as part of a scheme to minimize boundary effects. In the model foundation load tests, the local displacement measurement was used to monitor the distribution of displacement in the rock mass. This paper describes the techniques implemented in these two cases and discuses their performances.
Nano-carbon nitride synthesis from a bio-molecular target for ion beam sputtering at low temperature
(1999-03-01)
Wu, JJ
;
Lu, TR
;
Wu, CT
;
Wang, TY
;
Chen, LC
Nano-crystalline carbon nitride has been successfully synthesized at a temperature below 100 degrees C from an adenine(C5N5H5) target sputtered by an Ar ion beam. Because adenine possesses a ring structure similar to the hypothetical beta-C3N4 phase, the use of this bio-molecular compound as the target is believed to reduce the energy barrier of carbon-nitride growth. The effect of Ar ion-sputtering voltage on the film growth and the effect of extra-N-atom incorporation on the carbon-nitride film growth are examined in this study. Only a carbon film is formed with an ion energy of 500 V. For the ion-beam energy above 750 V, carbon nitride films are deposited, and there is some hydrogen incorporation in the films. The N/C composition ratio in the films could reach 1:1 and is independent on the ion beam voltage. The nitrogen is bonded with carbon within the films, as determined by the IR and XPS measurements. However, the films deposited at a higher ion voltage could possess some original functional groups of adenine. A strong and broad peak at a d-spacing of 0.32 nm, comparable to the calculated d-spacing of the beta-C3N4(110), is observed in the XRD spectra of the carbon nitride films. The TEM results indicated that the film contained nano-crystalline grains. Several d values are also in good agreement with those of adenine and the calculated values of beta-C3N4. The C/N ratios of the films are still kept at almost 1:1 with N atoms added during deposition. The XRD spectra and IR spectra of these films are all similar to the film deposited without nitrogen source. (C) 1999 Elsevier Science S.A. All rights reserved.
PPD: A practical parallel loop detector for parallelizing compilers
(1996)
Wu, CT
;
Yang, CT
;
Tseng, SS
;
資訊工程學系
;
Department of Computer Science
PPD: A practical parallel loop detector for parallelizing compilers on multiprocessor systems
(1996-11-01)
Yang, CT
;
Wu, CT
;
Tseng, SS
;
交大名義發表
;
資訊工程學系
It is well known that extracting parallel loops plays a significant role in designing parallelizing compilers. The execution efficiency of a loop is enhanced when the loop can be executed in parallel or partial parallel, like a DOALL or DOACROSS loop. This paper reports on the practical parallelism detector (PPD) that is implemented in PFPC (a portable FORTRAN parallelizing compiler running on OSF/1) at NCTU to concentrate on finding the parallelism available in loops. The PPD can extract the potential DOALL and DOACROSS loops in a program by invoking a combination of the ZIV test and the I test for verifying array subscripts. Furthermore, if DOACROSS loops are available, an optimization of synchronization statement is made. Experimental results show that PPD is more reliable and accurate than previous approaches.
PPD: A practical parallel loop detector for parallelizing compilers on multiprocessor systems
(1996-11-01)
Yang, CT
;
Wu, CT
;
Tseng, SS
;
資訊工程學系
;
Department of Computer Science
It is well known that extracting parallel loops plays a significant role in designing parallelizing compilers. The execution efficiency of a loop is enhanced when the loop can be executed in parallel or partial parallel, like a DOALL or DOACROSS loop. This paper reports on the practical parallelism detector (PPD) that is implemented in PFPC (a portable FORTRAN parallelizing compiler running on OSF/1) at NCTU to concentrate on finding the parallelism available in loops. The PPD can extract the potential DOALL and DOACROSS loops in a program by invoking a combination of the ZIV test and the I test for verifying array subscripts. Furthermore, if DOACROSS loops are available, an optimization of synchronization statement is made. Experimental results show that PPD is more reliable and accurate than previous approaches.
Self-aligned tantalum oxide nanodot arrays through anodic alumina template
(2006-04-01)
Wu, CT
;
Ko, FH
;
Hwang, HY
;
材料科學與工程學系奈米科技碩博班
;
Graduate Program of Nanotechnology , Department of Materials Science and Engineering
A novel strategy for fabricating the ordered nanodot arrays of tantalum oxide with anodic alumina film is proposed to serve the template. Anodic oxidation of Al on TaN film has been performed in oxalic acid and sulfuric acid electrolytes at various applied voltages for porous alumina formation. Anodising reaction proceeds in the sequence of growth of porous anodic alumina when the aluminum layer is consumed up to the underlying TaN, and the growth of tantalum oxide under the bottoms of the alumina pores occurred simultaneously. The nanostructure of the nanodot arrays was studied by scanning electron microscopy, and the chemical composition of nanodots was analyzed by X-ray photoelectron spectroscopy. The nanodots are composed of nonstoichiometric TaOx. The nanodot diameter demonstrated here ranges between 15 nm and 70 nm and density ranges between 10(11) /cm(2) and 10(10)/cm(2). (c) 2006 Elsevier B.V. All rights reserved.
Tdesign and fabrication of a three-dimensional long-stretch micro drive by electroplating
(2004)
Tai, WC
;
Wu, CT
;
Hsu, CP
;
Hsu, W
;
機械工程學系
Here a three-dimensional micoractuator is proposed by integrating an electro-thermal long stretch micro drive (LSMD) and mechanical hinge mechanism. The mechanical hinge is used to allow the LSMD to be lifted. One of the important issues in fabricating the lifted microactuator is the conducting circuit to actuate the microactuator. Here the electroplating process is used to fabricate the mechanical hinge structure and the LSMD, and then the mechanical hinge itself can act as the conductive circuit easily. The fabrication and testing result show that the three-dimensional LSMD of 2000 mum wide and 500 mum high can stand vertically with output displacement up to 56 mum at input voltage of 2 volts. However, it is found that the output displacement of three-dimensional LSMD is smaller than planar LSMD with substrate beneath due to the lacking of heat conduction at the same input voltage.
The design and fabrication of a movable O-shape micro-clamper
(2001)
Wu, CT
;
Hsu, WS
;
機械工程學系
;
Department of Mechanical Engineering
With the demanding of handling micro objects, the development of micro-clamper has emerged. Here an electro-thermally driven micro-clamper with adjustable vertical position is proposed. This micro-clamper is consisted of an adjusting unit and a clamping unit. The adjusting unit formed by four bimorph beams in the longitudinal direction can move the clamping unit vertically. The clamping unit formed by a pair of bimorph beams at the end of the adjusting unit is in the transversal direction. Due to the residual stress difference in the bimorph beam, at initial state, the adjusting unit in the longitudinal direction will bend upward, and the other two bimorph beams will also curl up to become a clamper. When the adjusting unit is heated, the whole device will move downwards. When the clamper unit is heated, two sides of the clamping unit will open up to a waiting state. It is hoped that the capability of adjusting the clamper in vertical position will provide larger operating range for the micro-clamper. The micro-clamper proposed here is batch-fabricated by surface micromachining. The testing results show that the adjusting unit can produce 8 mum downward displacement at input voltage of 2V and the clamping unit can be fully flattened around 5 V.
Using knowledge-based systems for research on parallelizing compilers
(2001-03-01)
Yang, CT
;
Tseng, SS
;
Fann, YW
;
Tsai, TK
;
Hsieh, MH
The main function of parallelizing compilers is to analyze sequential programs, in particular the loop structure, to detect hidden parallelism and automatically restructure sequential programs into parallel subtasks that are executed on a multiprocessor. This article describes the design and implementation of an efficient parallelizing compiler to parallelize loops and achieve high speedup rates on multiprocessor systems. It is well known that the execution efficiency of a loop can be enhanced if the loop is executed in parallel or partially parallel, such as in a DOALL or DOACROSS loop. This article also reviews a practical parallel loop detector (PPD) that is implemented in our PFPC on finding the parallelism in loops. The PPD can extract the potential DOALL and DOACROSS loops in a program by verifying array subscripts. In addition, a new model by using knowledge-based approach is proposed to exploit more loop parallelisms in this paper. The knowledge-based approach integrates existing loop transformations and loop scheduling algorithms to make good use of their ability to extract loop parallelisms. Two rule-based systems, called the KPLT and IPLS, are then developed using repertory grid analysis and attribute-ordering tables respectively, to construct the knowledge bases. These systems can choose an appropriate transform and loop schedule, and then apply the resulting methods to perform loop parallelization and obtain a high speedup rate. For example, the IPLS system can choose an appropriate loop schedule for running on multiprocessor systems. Finally, a runtime technique based on the inspector/executor scheme is proposed in this article for finding available parallelism on loops. Our inspector can determine the wavefronts of a loop with any complex indirected array-indexing pattern by building a DEF-USE table. The inspector is fully parallel without any synchronization. Experimental results show that the new method can resolve any complex data dependence patterns where no previous research can. One of the ultimate goals is to construct a high-performance and portable FORTRAN parallelizing compiler on shared-memory multiprocessors. We believe that our research may provide more insight into the development of a highperformance parallelizing compiler Copyright (C) 2001 John Wiley & Sons, Ltd.