Browsing by Author "Tseng, Wen-Shou"

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A High Efficiency Surface Modification Process for Multiwalled Carbon Nanotubes by Electron Cyclotron Resonance Plasma
(2008-11-27)
Tseng, Wen-Shou
;
Tseng, Chyuan-Yow
;
Chuang, Pi-Kai
;
Lo, An-Ya
;
Kuo, Cheng-Tzu
A novel process of surface modification for multiwalled carbon nanotubes (MWCNTs) by using electron cyclotron resonance plasma is proposed. The process uses a H(2)/O(2) gas mixture as etching gas and applies a bias voltage of -250 DCV to the process stage to extract and accelerate hydrogen and oxygen cations. The generated high density and high incident energy cations are employed to create defects on the surface of nanotubes through ion bombardment. The oxygen cations with high reduction potential are simultaneously applied, oxidizing the surface of the nanotubes so as to form functional groups on the side walls most effectively. Additionally, being far from the plasma sheath, the MWCNTs can be maintained at a lower temperature to prevent from being decomposed under the high energy plasma. The efficiency of this method was systematically analyzed using X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. The experimental results have shown that the proposed method is a highly effective way to functionalize MWCNTs, resulting in the nanotubes with high concentration of oxygen-containing functional groups and minimal structural damage within very short process time.
Effects of Gas Composition on Highly Efficient Surface Modification of Multi-Walled Carbon Nanotubes by Cation Treatment
(2009-03-01)
Tseng, Wen-Shou
;
Tseng, Chyuan-Yow
;
Kuo, Cheng-Tzu
;
材料科學與工程學系
;
Department of Materials Science and Engineering
High incident energy hydrogen and/or oxygen cations are generated by electron cyclotron resonance system, and then used to highly efficiently modify multi-walled carbon nanotubes (MWCNTs). The effects of various H(2)/O(2) gas compositions on the modification process are studied. A systematic characterization method utilizing a combination of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, Raman spectroscopy, and thermogravimetric analysis (TGA) is used to evaluate the effects of various H(2)/O(2) gas compositions on MWCNT functionalization. The Raman results show that the I (D)/I (G) ratio is directly affected by H(2) concentration in gas mixture, and the treatment applying a H(2)/O(2) gas mixture with ratio of 40/10 (sccm/sccm) can yield the nanotubes with the highest I (D)/I (G) ratio (1.27). The XPS results suggest that the gas mixture with ratio of 25/25 (sccm/sccm) is most effective in introducing oxygen-containing functional groups and reducing amorphous carbon. The TGA suggests that the structural change of the treated nanotubes is marginal by this method with any gas condition.
Formation of iridium nanocrystals with highly thermal stability for the applications of nonvolatile memory device with excellent trapping ability
(2010-10-04)
Wang, Terry Tai-Jui
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Chu, Chang-Lung
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Hsieh, Ing-Jar
;
Tseng, Wen-Shou
;
材料科學與工程學系
This paper presents the formation of iridium nanocrystals (Ir-NCs) embedded in SiO(2) matrix and it can be used for potential applications of nonvolatile memory devices. The NC formation is investigated by varying Ir film thickness; and the thermal agglomeration is also studied by applying various annealing temperatures and process time. The results of systematic characterization including capacitance-voltage, transmission electron microscopy, and x-ray photoelectron spectroscopy show that the high work-function (5.27 eV) metallic-NCs have a highly thermal stability (up to 900 degrees C) and the resulted Al/SiO(2)/Ir-NCs/SiO(2)/Si/Al stack can have a good retention ability and significant hysteresis window of 17.4 V. (C) 2010 American Institute of Physics. [doi:10.1063/1.3498049]
Formation of iridium nanocrystals with highly thermal stability for the applications of nonvolatile memory device with excellent trapping ability
(2010-10-04)
Wang, Terry Tai-Jui
;
Chu, Chang-Lung
;
Hsieh, Ing-Jar
;
Tseng, Wen-Shou
;
材料科學與工程學系
This paper presents the formation of iridium nanocrystals (Ir-NCs) embedded in SiO(2) matrix and it can be used for potential applications of nonvolatile memory devices. The NC formation is investigated by varying Ir film thickness; and the thermal agglomeration is also studied by applying various annealing temperatures and process time. The results of systematic characterization including capacitance-voltage, transmission electron microscopy, and x-ray photoelectron spectroscopy show that the high work-function (5.27 eV) metallic-NCs have a highly thermal stability (up to 900 degrees C) and the resulted Al/SiO(2)/Ir-NCs/SiO(2)/Si/Al stack can have a good retention ability and significant hysteresis window of 17.4 V. (C) 2010 American Institute of Physics. [doi:10.1063/1.3498049]
Functionalizing Multi-Walled Carbon Nanotubes Using ECR Plasma and a Mild Nitric Acid Treatment
(2009-12-01)
Tseng, Wen-Shou
;
Tseng, Chyuan-Yow
;
Kuo, Cheng-Tzu
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In the present work, a two-step process combining electron cyclotron resonance (ECR) plasma and 0.25 M nitric acid treatments is utilized to functionalize multi-walled carbon nanotubes (MWCNTs). In the process, high density and high incident energy hydrogen and oxygen cations generated by using ECR plasma system are used to bombard the MWCNTs for 5 min to break C-C bonds, creating free radical defects on the nanotube surface; the treated nanotubes are subsequently sonicated in the mild acid for 2 h, forming functional groups at the defects. Several characterization techniques, including X-ray photoelectron spectroscopy, scanning electron microscopy, Raman spectroscopy, and thermogravimetric analysis, are utilized to systematically evaluate the effect of the method. The results show that the MWCNTs treated by the presented method can contain a high concentration of oxygen-containing functional groups on the nanotube surface with the added advantage of high thermal stability and minimal destructive effects to the material structure.
Metal Oxide Film for Growing Vertically Aligned Single-Walled Carbon Nanotubes
(2009-08-01)
Tseng, Wen-Shou
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Wang, Wei-Hsiang
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Hong, Tasi-Hau
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Kuo, Cheng-Tzu
;
材料科學與工程學系
In the present study, we use a method that uses the oxidation state of platinum in Co-Cr-Pt oxide films to cause a volume expansion to form isolated nanoparticles through exposure to H(2) microwave plasma. The generated nanoparticles are then used to grow single-walled carbon nanotubes (SWCNTs) at similar to 600 degrees C without the application of a buffer layer using a microwave plasma chemical vapor deposition system. The effects of metal oxide film thickness on the growth of SWCNTs are investigated. The characterization techniques including X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy are carried out, with the results showing that this method used is highly efficient in generating very small and dense catalytic nanoparticles. The results also show that, when the metal oxide film thickness is no more than 2nm, the nanoparticles produced with diameters ranging from 2 to 3nm can be effective for growing vertically and densely aligned SWCNTs. (C) 2009 The Japan Society of Applied Physics
Optoelectronic properties in vertically aligned ZnO/Si-nanopillars
(2012)
Lee, Hsin-Yi
;
Chang, Yuan-Ming
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Tseng, Wen-Shou
;
Kao, Pin-Hsu
;
Wang, Hau-Wei
An effective method of fabricating vertically aligned silicon nanopillars (Si-NPs) was realized by using the self-assembled silver nanodots as natural metal-nanomask for subsequent etching process. Ultrathin (similar to 9 nm) ZnO films were deposited on the Si-NPs by atomic layer deposition to enhance the field emission property. The turn-on field defined by the 10 mu A/cm(2) current density criterion is similar to 0.74 V/mu m with an estimated beta similar to 1.33X10(4). The low turn-on field and marked enhancement in beta were attributed to the small radius of curvature, high aspect ratio, and perhaps more importantly, proper density distribution of the ZnO/Si-NPs. On the other hand, room-temperature ultraviolet (UV) luminescence was investigated for the atomic layer deposited ZnO films grown on Si nanowires fabricated by self-masking dry etching in hydrogen-containing plasma. For films deposited at 200 degrees C, an intensive UV emission corresponding to free-exciton recombination was observed with a nearly complete suppression of the defect-associated broad visible range emission peak.
Process and properties of the carbon nanotube assisted LiCoO(2) thin-film battery electrode by pulsed laser deposition
(2009-11-01)
Lo, An-Ya
;
Sun, Chuan-Shu
;
Tseng, Wen-Shou
;
Kuo, Cheng-Tzu
;
材料科學與工程學系
In this study, a pulsed laser deposition process was developed to deposit a carbon nanotube (CNT) assisted LiCoO(2) electrode to improve its power density. The electrodes were deposited on Pt-coated Si substrates with Ar and O(2) as sputtering gases and LiCoO(2)+C as the target. The results indicate that the working pressure is the most important parameter to control the composition of the electrode. Therefore, electrodes with a three-layer structure (i.e., LiCoO(2)-rich/CNT-rich/LiCoO(2)-rich) were fabricated by a three-step deposition process by varying the pressures from 13 to 1.3x10(4) Pa and then 13 Pa again, and it was found that the charge/discharge capacity became approximately 1.5 times greater than that in the corresponding electrode without a CNT-rich layer. The results also indicate that a higher substrate temperature is favorable for improving the crystallinity of the electrode to approach LiCoO(2) crystals.
Process and properties of the carbon nanotube assisted LiCoO2 thin-film battery electrode by pulsed laser deposition
(2009-11-01)
Lo, An-Ya
;
Sun, Chuan-Shu
;
Tseng, Wen-Shou
;
Kuo, Cheng-Tzu
;
材料科學與工程學系
In this study, a pulsed laser deposition process was developed to deposit a carbon nanotube (CNT) assisted LiCoO2 electrode to improve its power density. The electrodes were deposited on Pt-coated Si substrates with Ar and O-2 as sputtering gases and LiCoO2+C as the target. The results indicate that the working pressure is the most important parameter to control the composition of the electrode. Therefore, electrodes with a three-layer structure (i.e., LiCoO2-rich/CNT-rich/LiCoO2-rich) were fabricated by a three-step deposition process by varying the pressures from 13 to 1.3x10(4) Pa and then 13 Pa again, and it was found that the charge/discharge capacity became approximately 1.5 times greater than that in the corresponding electrode without a CNT-rich layer. The results also indicate that a higher substrate temperature is favorable for improving the crystallinity of the electrode to approach LiCoO2 crystals.