Browsing by Author "Wang, WH"

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Effect of thin film coating of Au on joint strength in Invar-Invar packages
(1996-11-01)
Wang, SC
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Wang, CM
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Wang, C
;
Chang, HL
;
Tu, YK
The effect of a thin film coating of Au on the joint strength, weld width, and penetration depth in laser welding techniques for Invar-Invar packages is investigated experimentally. It is found that the joint strength, weld width, and penetration depth are strongly dependent on the coating of Au thickness on the Invar material. The welded joints with thick Au coating show narrower weld width, shallower penetration, and hence less joint strength than those of the packages with thin Au coating. The increase in both the thermal conductivity and the vapor volume in the welded joints as the coating of Au thickness increases are the possible mechanisms for the reduction. Detailed knowledge of the effect of thin film coatings of Au on the welded materials, which gives both the highest joint strength and good adhesion, is essential for practical design and fabrication of reliable optoelectronic packaging.
Effects of buffer layer materials and process conditions on growth mechanisms of forming networks of SWNTs by microwave plasma chemical vapor deposition
(2005-11-01)
Wang, WH
;
Peng, YR
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Kuo, CT
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材料科學與工程學系
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Department of Materials Science and Engineering
This study investigates the growth mechanism of 1C compatible processes and to the feasibility of synthesizing networks of single-walled carbon nanotubes (SWNT-) at lower temperatures (similar to 610 degrees C) on Si wafer using microwave plasma chemical vapor deposition (MPCVD) with CH4 and H-2 as source gases. The effects of the buffer layer materials (ZnS-SiO2, Al2O3, AlON, and AlN) and process conditions on growth of carbon nanostructures with Co as catalyst were also examined, where the buffer layers and Co catalyst were deposited in sequence by physical vapor deposition (PVD), followed by H-plasma pretreatment before deposition of carbon nanostructures. Additionally, the morphologies and bonding structures of carbon nanostructures were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and Raman Spectroscopy. Analytical results demonstrate that networks of SIANTs are more favorable to be synthesized by selecting proper buffer layer material (e.g., AION), and under higher temperatures, thinner catalyst thickness (e.g., 5 run) and lower CH4/H-2 ratio (e.g., 5/100 sccm/sccm). The networks of SWNTs can be fabricated at temperatures as low as similar to 610 degrees C by manipulating these parameters. In conclusion, the growth mechanism determines the conditions for the formation of nano-sized extrusions on catalyst particles surface. (c) 2005 Elsevier B.V. All rights reserved.
Effects of the Sb2Te3 crystallization-induced layer on crystallization behaviors and properties of phase change optical disk
(2004-01-30)
Wang, WH
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Chung, LC
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Kuo, CT
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材料科學與工程學系
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Department of Materials Science and Engineering
The conventional phase-change optical disk is generally fabricated by the sputtering process, which has a drawback of requiring an initialization process to change the as-deposited recording layer in the disk from amorphous to crystalline phases before the disk can be used for reading or writing. In order to develop an initialization-free process, the Sb2Te3, alloy was used as an additional layer below or above the recording Ge2Sb2Te5 layer to study its effect on crystallization behaviors of the recording layer. The layer structures were deposited on substrates of Si wafer, Cu-mesh to examine crystal structure (XRD), amorphous-to-crystal transformation (DSC) and microstructure (TEM). The complete disk specimens were prepared on PC board to measure their dynamic properties, such as reflectivity, jitter and modulation (dynamic tester); and to examine the effects of laser pulse duration time, position and thickness of Sb2Te3, layer on static reflectivity of the disk (static tester), where Avrami coefficient 'q' in J-M-A rate equation can be derived. The results show that effect of Sb2Te3 layer is essentially to induce crystallization of Ge2Sb2Te5, recording layer from (110) plane of Sb2Te3 crystals. This is due to the fact that the crystallization temperature of Sb2Te3 crystal is 85 degreesC below that of Ge2Sb2Te5 crystal, in addition to a lower lattice mismatch between two crystals. The is in agreement with the J-M-A kinetic analyses that the rate controlling step for amorphous-crystal transformation in disk specimens with Sb2Te3 layer over 15-nm thickness is mainly governed by nucleation with q = 2.53-2.79 > 2.5 in J-M-A equation. Regarding the effects of Sb2Te3 layer on disk properties, the results show that under the 10 nm Ge2Sb2Te5, layer thickness, the Sb2Te3 assisted disks with lower Sb2Te3 layer thickness between 13 and 20 nm show the best combination of reflectivity and modulation. The most important advantage of this process is that the Sb2Te3-assisted disks require no initialization process, because the as-deposited disks can be directly written and erased. (C) 2003 Elsevier B.V. All rights reserved.
Growth mechanism and properties of the well-aligned-carbon-coated Si nanocones by MPCVD
(2005-11-01)
Chuang, PK
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Teng, IJ
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Wang, WH
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Kuo, CT
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材料科學與工程學系
in order to clarify the possibility to form Si nanocones under the same gas sources (CH4 and H,) and deposition system (microwave plasma chemical vapor deposition (MPCVD)), a process were successfully developed to synthesize the well-aligned amorphous carbon-coated Si nanocones (a:C-SNCs), and their growth mechanism is proposed. This process includes depositing 10 nm Co-catalyst on Si wafer by physical vapor deposition (PVD) and then followed by H-plasma pretreatment to form Co nanoparticles. The pretreated specimens were then used to synthesize various nanostructures under a higher negative Substrate bias. The deposited nanostructures and their compositions were characterized by SEM, HRTEM, ED, EDS and Raman spectroscopy. The results indicate that the most important parameters for forming a:C-SNCs include a lower CH4/H-2 ratio, a higher negative substrate bias and assistance of the carbon-soluble nano-sized catalysts, such as Co. Under a higher enough negative substrate bias (>= 240 V), the etching rates of the catalyst particles and the substrate by the positive species are greater than the carbon deposition rate; a:C-SNCs can be formed. We propose that the cone shape of the nanostructures is essentially resulted from a progressive reduction in catalyst particle sizes under the conditions of higher etching rate than deposition rate on the catalyst surfaces, which may be partially due to a reduction in the Co melting temperature by the presence of carbon in the Co matrix. This mechanism is supported by the facts that a:C-SNCs find no catalysts or very small catalysts on the tips; the catalyst sizes show no significant reduction in sizes after the same a:C-SNCs deposition conditions except no presence of carbon; the diameter of the cone base has no significant differences in size as the original catalyst size after H-plasma pretreatment. Our mechanism gives the guideline to form the nanocone structures by MPCVD with same gas sources (CH4 and H-2). (c) 2005 Published by Elsevier B.V.
Hot-carrier-induced degradation for partially depleted SOI 0.25-0.1 mu m CMOSFET with 2-nm thin gate oxide
(2002-12-01)
Yeh, WK
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Wang, WH
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Fang, YK
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Chen, MC
;
Yang, FL
Hot-carrier-induced degradation of partially depleted SOI CMOSFETs was investigated with respect to body-contact (BG-SOI) and floating-body (FB-SOI) for channel lengths ranging from 0.25 down to 0.1 mum with 2 nm gate oxide. It is found that the valence-band electron tunneling is the main factor of device degradation for the SOI CMOSFET. In the FB-SOI nMOSFET, both the floating body effect (FBE) and the parasitic bipolar transistor effect (PBT) affect the hot-carrier-induced degradation of device characteristics. Without apparent FBE on pMOSFET, the worst hot-carrier stress condition of the 0.1 mum FB-SOI pMOSFET is similar to that of the 0.1 mum BG-SOI pMOSFET.
Nanofabrication and properties of the highly oriented carbon nanocones
(2005-03-01)
Wang, WH
;
Lin, YT
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Kuo, CT
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材料科學與工程學系
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Department of Materials Science and Engineering
A process to fabricate Co-assisted carbon nanocones (CNCs) was successfully developed by using microwave plasma chemical vapor deposition (MP-CVD). The nanostructures could be manipulated by adjusting the ratios of the source gases (CH4/H-2=5/80-15/80 sccm/sccm) and the substrate bias (0 similar to-300 V). The properties of deposited nanostructures were characterized by field emission scanning electron microscopy (FESEM), Raman Spectroscopy, auger electron spectroscopy (AES) spectra. The results show that the nanostructures with cone shape are resulted from competition between the ion bombardment rate and the growing speed of the nanostructures in the plasma, where ion bombardment is drove by the presence of negative substrate bias. In other words, a higher substrate negative bias (>-150 V) and a lower concentration of carbon species in the plasma are favorable conditions to grow highly oriented CNCs due to a greater ion bombardment energy and lower lateral growth rate of the nanostructures, respectively. The results indicate that CNCs synthesized under the applied bias of -300 V show an excellent performance in field emission current density (up to similar to 173 mA/cm(2) at 10 V/mu m). (c) 2004 Elsevier B.V. All rights reserved.
Nanofabrication and the structure-property analyses of phase-change alloy-ended CNTs
(2006-02-24)
Wang, WH
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Chao, KM
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Teng, IJ
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Kuo, CT
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材料科學與工程學系
In order to cap the tip cavities of the open-ended carbon nanotubes (CNTs) with the phase-change alloy for potential applications as the nano-resolution storage media, the Co-assisted CNTs were first synthesized by electron cyclotron resonance chemical vapor deposition (ECR-CVD) with H-2 and CH4 as the gas sources. Then, the as-grown CNTs were post-treated in H-plasma atmosphere to remove the carbon layers covered on catalysts, and subsequently immersed in HNO3 solution to remove the catalysts from the tips. The open-ended CNTs with a bowl-like-shape tips were followed by coating with a phase-change alloy layer of GeSbTeSn via sputtering process, and then heat treated in vacuum for 30 min to trim the alloy off from the sidewalls of CNTs to obtain the alloy-ended CNTs. The structures and properties in each processing step were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and Auger electron spectroscopy (AES). The experimental results show that the well-oriented phase-change alloy-ended CNTs over a large area are fabricated successfully. Furthermore, the Auger analyses show the compositions of the phase-change alloys may be changed from Te-rich to Ge-rich after being capped on the tips of CNTs. (c) 2005 Elsevier B.V. All rights reserved.
Surface contact analysis for a spatial cam mechanism
(1997-06-01)
Wang, WH
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Tseng, CH
;
Tsay, CB
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交大名義發表
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機械工程學系
This paper proposes and analyzes a new meshing condition between a modified hyperboloidal roller follower and a spatial cam surface. This new geometrical model can be utilized to avoid the edge contact phenomenon between a cylindrical roller follower and its mating cam surface. In the new model a modified hyperboloidal roller follower is selected to replace the original cylindrical roller follower. Once the new spatial cam mechanism is modeled by means of surface contact analysis (SCA), the contact condition between the modified hyperboloidal roller follower and the cam surface is clearly derived. Errors in the displacement function and the contact path arising from assembly errors are also analyzed. This study assists the manufacture and assembly of more accurate and higher quality spatial cam mechanisms.
Surface contact analysis for a spatial cam mechanism
(1997-06-01)
Wang, WH
;
Tseng, CH
;
Tsay, CB
;
機械工程學系
;
Department of Mechanical Engineering
This paper proposes and analyzes a new meshing condition between a modified hyperboloidal roller follower and a spatial cam surface. This new geometrical model can be utilized to avoid the edge contact phenomenon between a cylindrical roller follower and its mating cam surface. In the new model a modified hyperboloidal roller follower is selected to replace the original cylindrical roller follower. Once the new spatial cam mechanism is modeled by means of surface contact analysis (SCA), the contact condition between the modified hyperboloidal roller follower and the cam surface is clearly derived. Errors in the displacement function and the contact path arising from assembly errors are also analyzed. This study assists the manufacture and assembly of more accurate and higher quality spatial cam mechanisms.