Browsing by Author "Kuo, C. T."

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A bio-inspired two-layer multiple-walled carbon nanotube-polymer composite sensor array and a bio-inspired fast-adaptive readout circuit for a portable electronic nose
(2011-07-15)
Wang, L. C.
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Tang, K. T.
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Chiu, S. W.
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Yang, S. R.
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Kuo, C. T.
We report a fully integrated, portable, battery-operated electronic nose system comprising a bio-inspired two-layer multiple-walled carbon nanotube (MWNT)-polymer composite sensor array, a bio-inspired fast-adaptive readout circuit, and a microprocessor embedded with a pattern recognition algorithm. The two-layer MWNT-polymer composite sensor is simple to operate, and the membrane quality can be easily controlled. These two-layer membranes have improved sensitivity and stability. The fast-adaptive readout circuit responds to the sensor response, while tuning out the long-term constant background humidity, temperature, and odors. This portable electronic nose system successfully classified four complex alcohol samples 40 times for each sample; these samples were sake, sorghum liquor, medical liquor, and whisky. (C) 2011 Elsevier B.V. All rights reserved.
A High-Performance Nanocomposite Material Based on Functionalized Carbon Nanotube and Polymer for Gas Sensing Applications
(2009)
Wang, L. C.
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Tang, K. T.
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Kuo, C. T.
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Yang, S. R.
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Sung, Yuh
The aim of this study is to develop a novel chemical gas sensing nanocomposite material. The traditional use for carbon nanotube in gas sensing polymer is to increase the composite's conductivity. However, we added functionalized carbon nanotube to fill the free volume of the sensing polymer films and enhance the gas absorption/desorption response time of these nanocomposites. These sensing materials were prepared by mixing functionalized multiwalled carbon nanotubes (MWNTs) and Poly (n, n dimethylamino propylsilsequioxane) SXNR polymer. These new materials were coated on the Surface Acoustic Wave (SAW) device, which is expected to increase its sensitivity in analyzing specific classes of vapors. The proposed materials showed an enhanced sensitivity upon exposure to ethanol and dimethyl methylphosphonate (Dmmp) vapors. Additionally, the performances of our nanocomposite film are much higher than those polymers without functionalized carbon nanotubes.
Effect of substrate bias on growth and properties of carbon nanotubes deposited under no hydrogen introduction by MPCVD
(2006-04-01)
Chuang, P. K.
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Teng, I. J.
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Wang, W. H.
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Kuo, C. T.
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材料科學與工程學系
In order to examine the consequence of replacing hydrogen gas with high substrate bias, processes were successfully demonstrated to fabricate various carbon catalyst-assisted nanostructures, including carbon nanotubes (CNTs), by microwave plasma chemical vapor deposition (MPCVD), under the pure CH4 as the only source gas and without additional H-2 gas introduction. The Si wafers were first deposited with catalyst by physical vapor deposition (PVD), and then followed by H-plasma pretreatment to obtain the well-distributed catalyst particles on wafer. The pretreated specimens were then deposited in MPCVD to manipulate the various carbon nanostructures. The main process parameters include catalyst material (Co, Ni and Fe), the substrate bias (0 to - 320 V), and deposition time (1 to 20 min). The as-deposited nanostructures were characterized by SEM, HRTEM, Raman spectroscopy, and field emission I-V measurement. The results indicate that the various nanostructures on Si wafers can be manipulated under sufficient high negative substrate bias (>-200 V) without the additional hydrogen introduction. These results also improve our understanding on growth mechanisms of CNTs or other nanostrucrures, where the most of the proposed mechanisms in the literature were too much emphasis on the role of hydrogen. On important process parameters, except the substrate bias, it is interesting to note that effect of deposition time on nanostructures is essentially to extend the more CNTs into the plasma zone, which can result in different purification effect on CNTs, vary the alignment and sizes of CNTs, and expose the more nanostructures near the substrate surface. Under the present deposition 2 conditions, the best nanostructures with the best field emission properties (Turn-on field = 5 V/mu m, maximum current density > 35 mA/cm(2)) are the well-aligned CNTs with proper tube number densities, purities and sizes. (c) 2005 Elsevier B.V. All rights reserved.
Low-temperature growth mechanism of SW-NTs networks by buffer layer-assisted MPCVD
(2006-04-01)
Wang, W. H.
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Peng, Y. R.
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Chuang, P. K.
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Kuo, C. T.
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材料科學與工程學系
We present the microstructures and growth mechanism of networks of single-walled carbon nanotubes (SWNTs) fabricated by buffer layer-assisted microwave plasma chemical vapor deposition (MPCVD) at relatively low temperatures. 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. Additionally, the surface roughness of buffer layer and its bonding structures with catalyst atom are analyzed by atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. Analytical results demonstrate that networks of CNTs are formed by bundles or individual SWNTs. We suggest that the formation of SWNTs networks at low temperature may follow the root-growth mechanism. The differences comparing with previous growth mechanism are that the nuclei formation resulted from the rough surface of the buffer layer, and dissolution of carbon in catalyst will be enhanced due to the surface diffusion of the buffer layer. These unique effects from the buffer layer can provide favorable conditions to grow SWNTs at relatively low process temperatures. (c) 2005 Elsevier B.V. All rights reserved.
Luminance enhancement of flip-chip light-emitting diodes by geometric sapphire shaping structure
(2008-01-01)
Lee, C. E.
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Kuo, H. C.
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Lee, Y. C.
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Tsai, M. R.
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Lu, T. C.
The flip-chip light-emitting diodes (FC-LEDs) with geometric sapphire shaping structure were investigated. The sapphire shaping structure was formed on the. bottom side of the sapphire substrate by a chemical wet etching technique for light extraction purpose. The crystallography-etched facets were (1010) M-plane, (1102) R-plane, and (1120) A-plane against the (0001) c-axis with the angles range between 29 degrees similar to 60 degrees. These large slope oblique sidewalls are useful for light extraction efficiency enhancement. The light-output power of sapphire shaping FC-LEDs was increased 55% (at 350-mA current injection) compared to that of conventional FC-LEDs.
Mechanical properties and fracture mechanism of porous SiOCH low-k dielectrics
(2011-07-01)
Chang, H. L.
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Kuo, C. T.
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Liang, M. S.
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材料科學與工程學系
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高階主管管理碩士學程
A series of low-k dielectric films with various mechanical properties were prepared for a 32-nm back-end-of-line technology node. Various precursors were used, and the porogen removal treatment was performed using the H(2) or E-beam-assisted method. This study presents a novel approach for determining the loss of materials during treatment. This approach includes determining yield strength, fracture toughness, bonding structure, and fracture mechanism of a series of low-k silica films. The results show that a low-k film formed using the precursor trimethylsilane has higher yield strength and fracture toughness than the low-k films formed using the precursor tetramethylsilane or octamethylcyclotetrasiloxane. The residual gas analysis was conducted to determine the loss of materials and predict the bonding structure: the results show that the E-beam treatment rearranges the structure more effectively than the H(2) treatment by using the H radial to decompose the methyl group. Finally, the fracture mechanism of these low-k films was determined by relating the crack patterns of the indents on these films to their indentation load-displacement curves. (C) 2011 Elsevier B.V. All rights reserved.
Nanostructured Material Formation for Beyond Si Devices
(2015)
Chang, H. L.
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Chang, C. T.
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Kuo, C. T.
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材料科學與工程學系
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Department of Materials Science and Engineering
Beyond Si CMOS technology is the current challenging for next generation transistor. As demand for nano-scaled devices increase, the ability to manipulate the building blocks of electronic is essential. Catalytic-assisted CNTs are integrated into trenches, holes, parallel plates under CH4/H-2 gases by microwave plasma chemical vapor deposition or electron cyclotron resonance deposition. The trench and parallel plates are used to fabricate for gate electrodes, while the holes are used to make interconnections. Results indicate the orientation of grown CNTs is dominated by pattern geometry. The field emission results show that the CNTs exhibit robust electronic properties with emission densities of over 1mA/cm(2) at 3.97 and 6.30 V/mu m indicating the high electron emission efficiency as the CNT field effect transistor application. The growth models of Fe, Ni and CoSi2 and application for nanoclectronics are purposed.
One-step growth process of carbon nanofiber bundle-ended nanocone structure by microwave plasma chemical vapor deposition
(2006-11-01)
Teng, I. J.
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Chuang, P. K.
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Kuo, C. T.
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材料科學與工程學系
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Department of Materials Science and Engineering
In this work, we report a simple one-step growth process to synthesize a novel and distinct carbon nanostructure, called a carbon nanofiber bundle-ended nanocone (CNFNC) structure, by using microwave plasma chemical vapor deposition (MPCVD) method with CH4 and H, as source gases and Fe catalyst. The nanostructures and their properties after each processing step were characterized by FESEM, HRTEM, ED, AES, and Raman spectroscopy. The preliminary results have demonstrated that the CNFNC structures exhibit excellent field emission properties. The results also show that the favored conditions to form the CNFNC structures include a combination of lower CH4/H-2 flow ratio, higher substrate negative bias, and proper working pressure and deposition time. The possible growth mechanism of the CNFNC structures is proposed. (c) 2006 Elsevier B.V. All rights reserved.
Study of Conduction Modes of Time to Dielectric Breakdown Reliability in Cu Damascene Structures
(2013)
Chang, H. L.
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Chang, C. T.
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Kuo, C. T.
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材料科學與工程學系
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Department of Materials Science and Engineering
Low k time-dependent dielectric breakdown is increasingly becoming a major issue at the 45 nm technology node and beyond. Although TDDB models, such as the root E model, the v E model and the 1/E model, have been extensively explored, determining the back end of line processing direction for TDDB warrants further study. This study attempts to determine whether the thickness of the etching stop layer film influences the electron conduction mechanism. Cu damascene structures were designed following three approaches with various thickness of the etching stop layer : Co/ESL = 0 A-550 A (low-k: SiCO k = 3.1), Cu/ESL = 0 A-275 A (low-k: SiCO k = 2.5) and Co/ESL = 0 A-275 A (low-k: SiCO k = 2.5). The application of capping material Co is warranted for electron emission suppression, but the oxygen attacking from subsequent low-k deposition is a concern. In addition, greater ESL thickness offers paths for electron conduction which worsens TDDB; i.e., less ESL thickness is better. Therefore, the combination of Co with SiH4 treatment addresses optimized conditions to achieve an ESL-less application for TDDB enhancement. (C) 2013 The Electrochemical Society. All rights reserved.
Study of InGaN-GaN Light-Emitting Diodes With Different Last Barrier Thicknesses
(2010-06-15)
Chen, Jun-Rong
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Lu, Tien-Chang
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Kuo, Hao-Chung
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Fang, K. L.
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Huang, K. F.
This work reports a theoretical and experimental study on the device performance of blue InGaN-GaN light-emitting diodes (LEDs) with different last barrier thicknesses. The experimental results show that the employment of a 25-nm-thick p-type GaN last barrier in GaN LEDs can improve the light output power from 35.6 to 40.2 mW at 50 mA. By using advanced device simulation, it is shown that the effective energy barrier created by the p-type AlGaN electron blocking layer (EBL) is significantly decreased due to the band bending at the interface between GaN last barrier and AlGaN EBL. The use of a p-type GaN last barrier before the growth of AlGaN EBL can provide a higher energy barrier to suppress the electron overflow and then enhance the light output power.
Super growth of vertically aligned SWCNTs using self-assembled nanoparticles from CoCrPtO(x) ultra-thin film
(2007-01-01)
Wang, W. H.
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Hong, T. H.
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Kuo, C. T.
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材料科學與工程學系
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Department of Materials Science and Engineering
The self-assembly of catalytic nanoparticles by the decomposition of an as-deposited oxidized CoCrPt thin film is investigated, and the feasibility of its use in fabricating vertically aligned SWCNT films at a low synthesis temperature (similar to 600 degrees C) by microwave plasma CVD is described. The XPS results indicate that small nanoparticles with the diameters of 3-3.5 nm were formed in the explosion associated with the reduction of PtO(2) in the CoCrPtO(x) film. Cr(2)O(3) is employed to inhibit the agglomeration of nanoparticles and Co is typically involved in the dissolution and precipitation of carbon species for SWCNT growth. These small, self-assembled catalytic nanoparticles obtained from the CoCrPtO(x) ultra-thin film can be used to fabricate an extremely dense and highly oriented SWCNT film oil a silicon wafer at a temperature of similar to 600 degrees C. (c) 2006 Elsevier Ltd. All rights reserved.
Super growth of vertically aligned SWCNTs using self-assembled nanoparticles from CoCrPtOx ultra-thin film
(2007-01-01)
Wang, W. H.
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Hong, T. H.
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Kuo, C. T.
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材料科學與工程學系
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Department of Materials Science and Engineering
The self-assembly of catalytic nanoparticles by the decomposition of an as-deposited oxidized CoCrPt thin film is investigated, and the feasibility of its use in fabricating vertically aligned SWCNT films at a low synthesis temperature (similar to 600 degrees C) by microwave plasma CVD is described. The XPS results indicate that small nanoparticles with the diameters of 3-3.5 nm were formed in the explosion associated with the reduction of PtO2 in the CoCrPtOx film. Cr2O3 is employed to inhibit the agglomeration of nanoparticles and Co is typically involved in the dissolution and precipitation of carbon species for SWCNT growth. These small, self-assembled catalytic nanoparticles obtained from the CoCrPtOx ultra-thin film can be used to fabricate an extremely dense and highly oriented SWCNT film oil a silicon wafer at a temperature of similar to 600 degrees C. (c) 2006 Elsevier Ltd. All rights reserved.