Growth of Carbon Nanofibers on Electroless Ni-P Alloy Catalyst
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GROWTH OF CARBON NANOFIBERS ON ELECTROLESS Ni-P ALLOY CATALYST T.K. Tsai, W.L. Liu, S.H. Hsieh, and W.J. Chen Department of Materials Science and Engineering, National Huwei Institute of Technology, Huwei, Yunlin, Taiwan 632, Republic of China Abstrate Carbon nanotubes (CNTs) were grown by electroless Ni–P plated on silicon substrate in a microwave heating chemical vapor deposition (CVD) system with methane gas at . The CNTs grown on Ni–P catalyst showed random orientation and small 700 diameter around 15∼30 nm. Field emission test results indicated that the Ni–P catalyzed–CNTs exhibited excellent field emission properties. The turn–on field was about 0.56 V/µm with an emission current density 10 µA/cm2 and the threshold field was 4.4 V/µm with an emission current density 10 mA/cm2. These excellent field emission properties may be attributed to the random orientation and small diameter of CNTs.
1. Introduction Since the discovery of carbon nanotubes (CNTs) in 1991,1 this kind of carbon nanostructures has attracted extensive attention and study, due to their novel properties and potential applications, such as in high–performing nano–materials, nanoelectronics, high–efficiency energy storage and cold field emitter.2-5 One of the most potential applications of CNTs is as electron emitter for flat plane displays. Because CNTs have excellent field emission properties, i.e., good emission stability, long emitter lifetime and low voltage for operating. Therefore, many researchs have been done on the fabrication of field emission display (FED) and other electronic devices. Several synthesizing methods for the fabrication of CNTs have been developed by researchers, such as arc discharge, laser evaporation, pyrolysis of hydrocarbon gases and plasma–enhanced or thermal CVD.5-10 Among these methods, the CVD possessed simple process, selective growth, high purity, high yield and vertical alignment characteristics. Thus CVD was widely accepted by many investigators. In the CVD method, the transition metal, e.g., Ni, Co, Fe, plays an important and indispensable role for the growth of CNTs, because it works as a catalyst of the CNTs, growth. The chemical composition and nanoparticle size of the catalyst determine the structure, property and diameter of the CNTs. Since the catalyst nanoparticles are essential for both initial nucleation and subsequent growth of CNTs in CVD, many investigations have been developed to prepare catalyst nanoparticles. The techniques include filling metallic catalyst nanoparticle in nanoporous or mesoporous zeolite, 11 silicon5 and anodic alumina12 by evaporation or impregnation, chemically synthesized catalyst metal nanoparticle by reverse micelle method,13 and etching the catalyst metal–coated substrate by laser ablation,8 plasma9 or NH3 treatment.14 Choi et al.15 deposited Ni using rf magnetron sputtering on Si substrate. Sohn et al.16 deposited Fe on Si (100) substrate by pulse–laser deposition. Avigal et al.17 coated Co on n–type Si by e–beam, and Kim et al.14 coated Ni using electropl
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