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Item type:Item, Effects of substrate pretreatments and catalyst applications on Si-C-N films and nanotube formations(2001-12-01) ;Chang, HL ;Kuo, CT ;材料科學與工程學系Department of Materials Science and EngineeringThe Si-C-N films were synthesized on Si substrates by a microwave plasma chemical vapor deposition (MPCVD) system with CH4, H-2 and N-2 as the source gases. Metal coating on Si columns were placed around the specimen and acted as catalyst and additional source of Si. Some of the Si substrates were mechanically polished or chemically etched with HF-KIO3-H2O solutions to obtain different surface roughness before film depositions. Effects of the substrate pretreatment and the action of catalysts on surface morphologies, compositions, band structure, field emission of the films were examined. Nanotubes or nanowires structures were found for films deposited on no-treatment substrate using Fe, Co and Pt catalysts. However, chemical etching substrate can enhance formation of crystals and film nucleation with or without the addition of catalyst. This was the first work to demonstrate the possibility of fabricating the Si-C-N nanotubes through use of the catalysts and by controlling the deposition conditions by MPCVD. Under the present deposition conditions and by using Fe catalyst, the lowest turn-on voltage of the films can be as low as 1.3 V/mum, while the corresponding emission current density at field strength of 20 V/mum can go beyond 2000 muA/cm(2).Item type:Item, Field emission, structure, cathodoluminescence and formation studies of carbon and Si-C-N nanotubes(2002-03-01) ;Chang, HL ;Lin, CH ;Kuo, CT ;材料科學與工程學系Department of Materials Science and EngineeringCatalyst growth carbon and Si-C-N nanotubes have been synthesized successfully by microwave plasma chemical vapor deposition (MPCVD) method using CH4 + H-2 or CH4 + N-2 as gas sources, Si columns as additional Si solid sources, and Fe, Fe-Y, Co-Ni as catalysts. Nanotubes consisting of Si, C and N were made under process gases of CH4 + N-2, and with or without additional Si columns. Well-aligned and nested nanotubes were observed dependent on the catalyst materials. Besides, Si-C-N nanotubes were observed as bamboo-Eke structure. The as-grown nanotubes were purified in an air furnace to investigate their CL signal shift for potential application involving blue light emission. The field emission results indicate that the emission current densities can be above 10 mA/cm(2) at 10 V/mum, and aligned nanotubes belong to better current stability at a constant electric field than nested nanotubes. Nanotubes with a low I-D/I-G ratio (=0.23) via Raman analysis are achieved. The mechanisms of formation for carbon nanotubes and Si-C-N nanotubes are also discussed. (C) 2002 Elsevier Science B.V. All rights reserved.Item type:Item, Growth of the large area horizontally-aligned carbon nanotubes by ECR-CVD(2002-12-02) ;Hsu, CM ;Lin, CH ;Chang, HL ;Kuo, CT材料科學與工程學系For potential applications of carbon nanotubes (CNTs) as connectors in microelectronic devices, the process to synthesize the large area horizontally-aligned CNTs on 100 mm (4 inch) Si wafers was developed, using electron cyclotron resonance chemical vapor deposition, with CH, and H, as the source gases and Co as the catalyst. The results show that vertical and horizontal CNTs can be obtained by manipulating the electric field applied on the substrate and flow direction of the gases. In the present deposition conditions, the horizontal CNTs show better field emission properties than vertical CNTs. This may be due to the blocking effect of catalysts at the tips and to the diminishment of the effective emission area from defects of vertical CNTs body. (C) 2002 Elsevier Science B.V. All rights reserved.Item type:Item, Iron and cobalt silicide catalysts-assisted carbon nanostructures on the patterned Si substrates(2002-12-02) ;Chang, HL ;Lin, CH ;Kuo, CT ;材料科學與工程學系Department of Materials Science and EngineeringCatalyst-assisted carbon nanotubes (CNTs) and carbon nano-rods were synthesized on the patterned or un-patterned Si wafer by microwave plasma chemical vapor deposition, using iron or cobalt silicide catalysts. Controllable carbon nanostructures were achieved by manipulating carbon and nitrogen concentration in the source gases, catalyst materials, and patterned wafer application. CNTs were synthesized under a high ratio of CH4/H-2 = 0.1, while carbon nano-rods were synthesized under a low ratio of CH4/H-2=0.01. Introducing N-2 gas into CH4/H-2 source gases gives rise to bamboo-like CNTs formation. Selective CNTs depositions were applied on (a) parallel Fe-coated line arrays, (b) CoSix-coated hole arrays. This is a novel method that is compatible with Si microelectronic device manufacturing. The field emission results indicate that the emission current density can be above 1 mA/cm(2) at 3.97 V/mum, and hollow like CNTs belong to better emission current than bamboo-like CNTs. Growth models of different carbon nanostructures are proposed. (C) 2002 Elsevier Science B.V. All rights reserved.