Electron Emission of Vertically Aligned Carbon Nanotubes Grown on a Large Area Silicon Substrate by Thermal Chemical Vap
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Electron Emission of Vertically Aligned Carbon Nanotubes Grown on a Large Area Silicon Substrate by Thermal Chemical Vapor Deposition
Cheol J. Lee1, Jung H. Park1, Kwon H. Son1, Dae W. Kim1, Tae J. Lee1, Seung C. Lyu1, Seung Y. Kang2, Jin H. Lee2, Hyun K. Park3, Chan J. Lee3, and Jong H. You3 1
School of Electrical Engineering, Kunsan National University, Kunsan 573-701, Korea
Microelectronics Lab., Next Generation Semiconductor Dept., ETRI, Taejon 305-350, Korea
2
Flat display Labs., R&D Center, Samsung Information Display Co., Suwon 442-391, Korea
3
ABSTRACT We have grown vertically aligned carbon nanotubes on a large area of Co-Ni codeposited Si substrates by thermal chemical vapor deposition using C2H2 gas. The carbon nanotubes grown by the thermal chemical vapor deposition are multi-wall structure, and the wall surface of nanotubes is covered with defective graphite sheets or carbonaceous particles. The carbon nanotubes range from 50 to 120 nm in diameter and about 130 µm in length at 950 oC. Steric hindrance between nanotubes at an initial stage of the growth forces nanotubes to align vertically. The turn-on voltage was about 0.8 V/µm with a current density of 0.1 µA/cm2 and emission current reveals the Fowler-Nordheim mode.
INTRODUCTION Since the first observation of carbon nanotubes [1], extensive researches have been done for the synthesis using arc discharge [2-4], laser vaporization [5], pyrolysis [6], and plasmaenhanced chemical vapor deposition (CVD)[7]. Although massive production of carbon nanotubes has been realized by arc discharge and laser vaporization [5], controlling diameters,
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lengths, and preferable alignment of carbon nanotubes has never been easily accessible with such approaches. Synthesis of well-aligned carbon nanotubes with high quality on a large area is necessary for their applications, such as flat panel displays. Thermal CVD is a useful method to grow damageless carbon nanotubes on a substrate. We have grown carbon nanotubes on a large area substrates by thermal CVD using acetylene gas. In this work, we report the growth of well aligned carbon nanotubes on a large area of Co-Ni codeposited Si substrates, and also evaluate electron emission of vertically aligned carbon nanotubes.
EXPERIMENTAL The p-Si substrates with a resistivity of 15 were thermally oxidized with the layer thickness of 300 nm. Co-Ni (Co:Ni=1:1.5) metal alloys with 100 nm in thickness were thermally evaporated in a vacuum of 1.5 10-6 torr on oxidized Si(100) substrates. The samples were dipped for 100-200 sec in diluted HF solution and then loaded on a quartz boat inside the CVD quartz reactor. Argon(Ar) gas was flowed into the quartz reactor in order to prevent the oxidation of catalytic metal alloys while increasing the temperature. Samples were pretreated using NH3 gas with a flow rate of 50-200 sccm for 10-30 min at 850-950 oC. Carbon nanotubes were grown using C2H2 gas with a flow rate of 20-80 sccm for 10-20 min at the same temperature. The reactor was cooled down slowly to room temperat
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