Large Field Emission from Vertically Well-aligned Carbon Nanotubes
- PDF / 1,823,570 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 67 Downloads / 227 Views
Large Field Emission from Vertically Well-aligned Carbon Nanotubes Jung Inn Sohn and Seonghoon Lee* Dept. of Materials Science and Engineering, Kwangju Institute of Science and Technology (K-JIST), Kwangju, Korea 500-712. Yoon-Ho Song, Sung-Yool Choi, Kyoung-Ik Cho, Kee-Soo Nam, Young-Il Kang Micro-Electronics Tech. Labs., ETRI, Taejon, Korea 305-350. ABSTRACT We have grown well-aligned carbon nanotube arrays by thermal chemical vapor deposition at 800ºC on Fe nanoparticles deposited by a pulsed laser on a porous Si substrate. Porous Si substrates were prepared by the electrochemical etching of p-Si(100) wafers with resistivities of 3 to 6 Ωcm. These well-aligned carbon nanotube field emitter arrays are suitable for electron emission applications such as cold-cathode flat panel displays and vacuum microelectronic devices like microwave power amplifier tubes. Field emission characterization has been performed on the CNT-cathode diode device at room temperature and in a vacuum chamber below 10-6 Torr. The anode is maintained at a distance of 60µm away from the carbon nanotube cathode arrays through an insulating spacer of polyvinyl film. The measured field emitting area is 4.0x10-5cm2. Our carbon nanotube field emitter arrays emit 1mA/cm2 at the electric field, 2V/µm. And they emit a large current density as high as 80mA/cm2 at 3V/µm. The open tip structure of our carbon nanotubes and their good adhesion through Fe nanoparticles to the Si substrate are part of the reason why we can attain a large field emission current density within a low field. The field emitter arrays in our diode device are vertically well-aligned carbon nanotubes on the Si-wafer substrate. INTRODUCTION Carbon nanotubes are known for their superior mechanical strength and low weight(tensile modulus ~1Tpa)[1], good heat conductance(heat conductivity of MWNT bundles ~1200W/m•K) [2], varying electronic properties depending on their helicity and diameter[3], large surface area useful for adsorption of hydrogen or other gases(H2 can be stored on 98wt% pure SWNTs up to ~7wt%.)[4], and their ability to emit a cold electron at a relatively low voltages due to high A14.9.1
aspect ratios and nanometer size tips[5]. Therefore, carbon nanotubes can be applied to field emitters for flat-panel displays[6] and vacuum microelectronic devices like microwave power amplifier tubes, nano-FETs[7], nano-Schottky diodes, ion storage for batteries, and mechanical structures requiring low weight and high strength. In this study, we’ll focus on the field emission properties of carbon nanotubes. The electric field ET at the tip of end radius r and voltage V with respect to a distant anode is given approximately by ET ~V/5r[8]. It is known that positive ions formed in the gate region sputter off the emitting diamond or Mo tip. Because of carbon nanotubes nanometer scale and their high aspect ratio more than ~300 and high mechanical strength and chemical stability, carbon nanotubes are very attractive as electron field emitters. Several groups have reported electron field e
Data Loading...
