Thin Multiwall Carbon Nanotube Field Emitters with Microchannel Plate for High Current Emission
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0891-EE07-05.1
Thin Multiwall Carbon Nanotube Field Emitters with Microchannel Plate for High Current Emission Raghunandan Seelaboyina, Jun Huang, Won Bong Choi Center for Nanomaterials and Devices, Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174, USA, [email protected]
ABSTRACT We report on a method to amplify the electron current of carbon nanotube field emitter cathode using an electron multiplier and synthesis of thin multiwall carbon nanotubes by thermal chemical vapor deposition. A commercial microchannel plate which is an array of microscopic electron multipliers was used for this purpose. A microchannel plate placed between the cathode and anode amplified the current 3 times and also acted as protection shield for nanotubes during vacuum arcing. The increase in current is attributed to the electron multiplication, and the increase in field enhancement factor from 9300 to 12800 (37%) with microchannel plate. The thin multiwall carbon nanotubes were synthesized using Mo/Fe catalyst solution. The inner and outer wall diameters of the nanotubes were in the range of 2.5-5 nm and 7-15 nm respectively, determined by Raman spectroscopy and transmission electron microscopy. The nanotubes had excellent field emission property which is attributed to their thin wall diameters ~10 nm, high aspect ratio of 800 and the resulting high field enhancement factor of 9300. The emission current was stable with an average fluctuation of 2%. INTRODUCTION Carbon nanotube field emitters have shown great promise as cathodes in many applications including field emission displays and high-power radio-frequency devices, [1-4]. Unique properties of carbon nanotubes (CNTs) include high current density [5], low threshold field for emission, instantaneous response to field variation, good on/off ratio, resistance to temperature fluctuations, high durability and power efficiency make them ideal candidate for many of these applications. Here we report a novel method of placing a microchannel plate, which is an array of microscopic electron multipliers on top of the CNT emitters. This new approach provides two benefits; it amplifies the electron current and protects CNTs from irreversible damage in the event of vacuum arcing. Microchannel plate (MCP) operates by avalanche multiplication of secondary electrons [6], secondary electrons are generated when incident electrons strike the channel walls of MCP. A voltage applied across the ends of the MCP creates a field which accelerates the secondary electrons along the channel generating more electrons leading to avalanche multiplication. Micro channel plates are used in many applications; one of them is in high efficiency field emission display as demonstrated by Lee et al. [7]. A commercial MCP made out of lead silicate glass obtained from Hamatsu was used for this study We synthesized thin multiwall carbon nanotubes which have shown good field emission properties in comparison with single and multiwall carbon nanotubes. Singlewall carbon nanotub
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