Browsing by Author "Tsai, CL"

Now showing 1 - 12 of 12

Bias effect on the growth of carbon nanotips using microwave plasma chemical vapor deposition
(2002-07-22)
Tsai, CL
;
Chen, CF
;
Wu, LK
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Carbon nanotips with a high-aspect ratio were directly grown on Pt films. Carbon nanotips grew up to 5.4 mum length and 64 nm diameter under a -120 V bias. Compared to the hollow structure of carbon nanotubes, transmission electron microscopy images indicate its solid body, which is made of graphite. Carbon nanotips possess good field emission characteristics, that is, a turn-on field of 1.5 V/mum and 761 muA/cm(2) under 2.2 V/mum. The Pt films provide a good conduction path for electron transport from the cathode to the emission site and do not act as catalysts. (C) 2002 American Institute of Physics.
Characterization of bias-controlled carbon nanotubes
(2003-09-01)
Tsai, CL
;
Chen, CF
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this study, we focus on the immediately improving quality of growing carbon nanotubes without any pre- or post-treatment. The applied biases during the reaction can directly control the diameter and the quality of carbon nanotubes. This simple step skips additional treatments and is easily used in many deposition systems. The diameter of carbon nanotubes noticeably varies from 45 nm without any amorphous carbon (under + 80 V) to 120 nm (under - 120 V). Raman spectrums indicate that I-D/I-G ratio decreases with increasing positive bias. This implies applying positive bias could enhance the graphitization of carbon nanotubes. However, positive and negative bias effects slightly vary the field emission enhancement. In addition, carbon nanotubes grown under positive bias possess better field emission characterization. This results from the following reasons: (I) smaller diameter- (II) pure surface; (III) more graphitized structure; and (IV) higher field enhancement beta. (C) 2003 Elsevier Science B.V. All rights reserved.
Characterization of phosphorus-doped and boron-doped diamond-like carbon emitter arrays
(2001-11-01)
Tsai, CL
;
Chen, CF
;
Lin, CL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We synthesized phosphorus-doped and boron-doped emitters by using trimethylphosphite P(OCH3)(3) and trimethylborate B(OCH3)(3) as doping sources in a microwave plasma chemical vapor deposition system. Based on our experimental results from scanning electron microscopy and Raman spectra, there is much difference among undoped, phosphorus-doped, and boron-doped diamondlike material. In addition, doping both phosphorus and boron can enhance electric properties by reducing the turn-on voltage and can increase the emission current density. The turn-on voltages of undoped, boron-doped, and phosphorus-doped emitters in triode-type field emitter arrays are 15, 8, and 5 V, respectively. The emission currents of boron-doped and phosphorus-doped emitters are about 20 and 80 times larger than the undoped. (C) 2001 American Institute of Physics.
Electronic properties of phosphorus-doped triode-type diamond field emission arrays
(2001-11-01)
Chen, CF
;
Tsai, CL
;
Lin, CL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this work, we present a novel scheme that involves a new fabrication process of gate structure metal-insulator-semiconductor (MIS) diode using IC technology. We use a bias-assisted microwave plasma chemical vapor deposition (BAMPCVD) system to synthesize P-doped and B-doped diamond. Based on our experimental results, it showed dendrite-like diamond with non-doped and nanotube-like diamond with B- or P- doping. Doping phosphorus or boron can enhance its electric characteristic by reducing the turn-on voltage and enhancing the emission current density. The turn-on voltage of non-doped, B-doped and P-doped is 15, 8 and 5 V, respectively. The field emission current (I-a) of non-doped, B-doped and P-doped is 4 muA (at 45 V), 76 muA (at 77 V) and 322 muA (at 120 V), respectively. (C) 2001 Elsevier Science B.V. All rights reserved.
Evaluation of reinforced connections between steel beams and box columns
(2004-11-01)
Chen, CC
;
Lin, CC
;
Tsai, CL
;
土木工程學系
;
Department of Civil Engineering
This study elucidates the cyclic behaviour of connection between a steel beam and a welded box column. Distribution of stresses at the joint between beam and box column inherently differ from those of the joint to the H-shaped column, as confirmed by finite element analysis. Six large-scale specimens were designed. A specimen with an unreinforced connection was tested initially to clarify its performance. The test results indicated that brittle fracture occurs at the beam flange complete joint penetration weld and in the weld access hole region, because the stresses are concentrated in these regions. Nevertheless, specimens reinforced by vertical rib plates on beam flanges achieve an inelastic rotation of more than 3% rad prior to failure by forming a plastic hinge in the beam away from the beam-to-column interface. The test results also revealed that welding diaphragm inside the box column is crucial during the welding process to the integrity of the connection, ensuring that beam forces are transferred to the connection. (C) 2004 Elsevier Ltd. All rights reserved.
Fabrication and characterization of phosphorus-doped diamond field emitters in triode-type field emission arrays
(2001-03-01)
Chen, CF
;
Tsai, CL
;
Lin, CL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this work, we present a novel scheme that involves a new fabrication process for gate-structured metal-insulator-semiconductor (MIS) diodes using IC technology. Using a bias-assisted microwave-plasma chemical vapor deposition (BAMPCVD) system to synthesize P-doped emitters completes this process. A comparison of the held emission characteristics of two types of non-doped dendrite-like and P-doped nanotube-like diamond emitters with a 4-mum gate aperture is made. Phosphorus doping can enhance the electrical characteristics by reducing the turn-on voltage and enhancing the emission current density. The turn-on voltage of non-doped and P-doped emitters is 15 and 5 V, respectively. Phosphorus doping can enhance the electrical properties by increasing the emission current, since the field emission current (I-a) of non-doped and P-doped emitters is 4 muA (at V-gc = 45 V) and 322 muA (at V-gc = 120 V), respectively. The emission current of P-doped emitters is approximately 80-fold larger than that of non-doped diamond emitters. (C) 2001 Elsevier Science B.V. All rights reserved.
Field emission from well-aligned carbon nanotips grown in a gated device structure
(2002-03-11)
Tsai, CL
;
Chen, CF
;
Lin, CL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Vertically well-aligned, high-aspect-ratio carbon nanotips have been directly grown upward on the gated device structure with 4 mum gate aperture. The nanotips rapidly nucleate and grow without any catalyst. In addition, selected area deposition of nanotips is achieved by using a Pt layer as inhibitor in the bias-assisted microwave plasma chemical vapor deposition. The field emission current of nanotips on the gated structure is 154 muA (at a gate-to-cathode voltage of V-gc=50 V). This results from the following reasons: (i) short gate-tips spacing, (ii) small gate aperture, and (iii) the high-aspect ratio of nanotips. (C) 2002 American Institute of Physics.
Influence of the condenser on sample tracking via forward scattering pattern detection
(2004)
Tsai, CL
;
Chang, BJ
;
Huang, KL
;
Hsu, L
;
電子物理學系
Sample tracking with a high spatial sensitivity is highly desired in force measurement with optical tweezers. However, the trick that sample tracking via forward scattering pattern detection would provide a higher sensitivity than that via regular image detection has never been investigated. In this paper, we systematically study the influences of the position and the numerical aperture of the condenser on sample tracking via forward scattering pattern detection. In our experiment, a 60X condenser is used to form the forward scattering pattern of a sample bead upon a CCD camera. As the bead is transversely shifted at a step size of 30nm by a PZT XYZ stage, we measure the magnitude of the corresponding shift of the forward scattering pattern when the 60X condenser of different angular apertures is placed at various locations along the optical axis. Our result shows that the most sensitive forward scattering pattern occurs when the condenser collimates the forward scattering light from the sample bead. We also find that the larger the numerical aperture is, the higher the sensitivity of forward scattering pattern detection will be.
Modification of new carbon based nano-materials for field emission devices
(2003-05-01)
Chen, CF
;
Tsai, CL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Field emission display (FED) is evolving as a promising technique of flat panel displays in the future. In this paper, various carbon based nanostructures are acted as cathode materials for field emission devices. Dendrite-like diamond-like carbon emitters, carbon nanotubes, carbon nanotips are synthesized by microwave plasma chemical vapor deposition. Many factors affect the performance of field emitters, such as the shape, work function and aspect ratio of emission materials. Modified process of carbon based nano-materials for enhancing field emission efficiency are included intrinsic and extrinsic process. These reformations contain the p-type and n-type doping, carburization and new ultra well-aligned carbon nano-materials. It is found that carbon nano-materials grown on micropatterned diode show higher efficiency of FED. In addition, to achieve a low- turn-on field, the novel scheme involving a new fabrication process of gated structure metal-insulator-semiconductor (MIS) diode by IC technology is also presented.
Self-embedded nanocrystalline chromium carbides on well-aligned carbon nanotips
(2003-06-16)
Tsai, CL
;
Hsu, JH
;
Chen, CF
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Well-aligned carbon nanotips embedded with nanocrystalline chromium carbide were directly grown on a substrate by microwave plasma chemical vapor deposition. These nanomaterials grew up to about 1 mum long and 60 nm in diameter, yielding a high aspect ratio. In comparison between carbon nanotubes with hollow structure, transmission electron microscopy images show its solid body, which is made of graphite along with nanocrystalline chromium carbide on the tip. These nanomaterials perform well in field emission applications with a turn-on field of 1.38 V/mum and 565 muA/cm(2) at 2.2 V/mum. Our result confirms the possibility of the self-embedded nanocrystalline materials on the top of carbon nanotips. (C) 2003 American Institute of Physics.
Study of carbon nanoemitters using CO2-CH4 gas mixtures in triode-type field emission arrays
(2002-03-01)
Chen, CF
;
Tsai, CL
;
Lin, CL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this study. we used methane/carbon dioxide gas mixtures to deposit nanoemitters on the gate-structured metal-insulator-semiconductor (MIS) diodes. Due to the nanoemitters growing in a high carbon concentration gas source of CH4/CO2, the growth rate is better than conventional mixtures by using hydrocarbons diluted in hydrogen. Moreover, the bias also promotes the growth rate in the CH4/CO2 gas mixtures. In addition, selected area deposition (SAD) of emitters was successfully achieved by using the Pt layer as inhibitor in the bias assisted microwave plasma chemical vapor deposition (BAMPCVD). The field emission. current and the current density of nanoemitters on field emission arrays (FEAs) are 154 LA and 490 mA cm(-2), respectively. This may be due to the following reasons: (I) short gate-emitter spacing; (II) small gate aperture; and (III) emitter with a sharp feature. (C) 2002 Elsevier Science B.V. All rights reserved.
The characterization of boron-doped carbon nanotube arrays
(2003-09-01)
Chen, CF
;
Tsai, CL
;
Lin, CL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this study, we directly synthesized boron-doped carbon nanotubes (CNTs) by using trimethylborate (B(OCH3)(3)) as doping sources in a microwave plasma chemical vapor deposition system (MPCVD). Doping boron causes the growth rate of CNTs to decrease. This might be due to the high oxygen content contained in the doping source that induces oxidation of graphite. The bamboo-like nanostructure of the carbon tubes disappeared with boron doping. Raman spectrum shows the higher I-D/I-G ratio in boron-doped CNTs. This implies the decrease of graphitization in boron-doped CNTs. In addition, doping boron could enhance the field emission property by increasing the current density by more than 30% (from 350 to 470 mA/cm(2) at 2.2 V/mum). (C) 2003 Elsevier Science B.V. All rights reserved.