Abstract
In this study, a simple, efficient, and economical process is reported for the direct synthesis of carbon nanotube (CNT) field emitters on metal alloy. Given that CNT field emitters can be customized with ease for compact and cold field emission devices, they are promising replacements for thermionic emitters in widely accessible X-ray source electron guns. High performance CNT emitter samples were prepared in optimized plasma conditions through the plasma-enhanced chemical vapor deposition (PECVD) process and subsequently characterized by using a scanning electron microscope, tunneling electron microscope, and Raman spectroscopy. For the cathode current, field emission (FE) characteristics with respective turn on (1 μA/cm2) and threshold (1 mA/cm2) field of 2.84 and 4.05 V/μm were obtained. For a field of 5.24 V/μm, maximum current density of 7 mA/cm2 was achieved and a field enhancement factor β of 2838 was calculated. In addition, the CNT emitters sustained a current density of 6.7 mA/cm2 for 420 min under a field of 5.2 V/μm, confirming good operational stability. Finally, an X-ray generated image of an integrated circuit was taken using the compact field emission device developed herein.
Highlights
Due to their strong C–C covalent bonds and high aspect ratio [1], carbon nanotubes (CNTs) exhibit extraordinary properties, such as high thermal conductivity, good chemical stability, and high mechanical strength
Given that catalyst seeds, such as Ni, Cr, Fe, Co, and Mo, are needed for the nucleation of CNTs, many reports emphasize the direct growth of CNTs on metal alloy substrates such as alloys of Ni, Fe, and the Cr (NFC alloy) system [7,8,9,10,11]
We have recently proposed a simpler and economical way to directly synthesize CNT emitters on a metal alloy substrate with sufficient field emission for a custom built, open type X-ray system that can be used for biomedical applications [12]
Summary
Due to their strong C–C covalent bonds and high aspect ratio [1], carbon nanotubes (CNTs) exhibit extraordinary properties, such as high thermal conductivity, good chemical stability, and high mechanical strength These properties make developing CNTs as cold field emitters very appealing for X-ray, microwave, and field emission display applications [2,3,4]. Given that catalyst seeds, such as Ni, Cr, Fe, Co, and Mo, are needed for the nucleation of CNTs, many reports emphasize the direct growth of CNTs on metal alloy substrates such as alloys of Ni, Fe, and the Cr (NFC alloy) system [7,8,9,10,11] By using these metal alloy substrates (with or without surface modification), separate processes involving the sputtering of the above mentioned active catalysts and/or reagents, such as HNO3 and HCl, can be avoided. The CNT emitters are custom developed for the assembly of a compact field emission device that can replace thermionic emitters in conventional electron guns, and can play a significant role in the development of multi X-ray source systems
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