Stability of electron field emission in Q-carbon
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Research Letter
Stability of electron field emission in Q-carbon Ariful Haque and Jagdish Narayan, Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695.7916, USA Address all correspondence to Ariful Haque at [email protected] (Received 9 May 2018; accepted 9 August 2018)
Abstract In this study, we have investigated electron field emission (EFE) characteristics of Q-carbon at room temperature and above. At room temperature the Q-carbon requires only ∼2.4 V/μm electric field to turn-on the EFE. The EFE properties of the Q-carbon composite structure improve with temperature by lowering the turn-on field and increasing the current density. At 500 K we observed a turn-on field of ∼2.34 V/μm, and a maximum current density was found to be ∼53 µA/cm2 at 2.66 V/μm. The Q-carbon field emitters also show very stable EFE characteristics (within 7% fluctuations) over time for current intensities between 7.5 and 47 µA/cm2.
Introduction Electron field emission (EFE) is considered as the only electron emission process compatible with the vacuum electronics due to the fast response time, low power consumption, cathoderay-tube-like colors, and wide viewing angles.[1,2] However, incorporation of cold field emitters in practical electronic devices is still quite challenging due to the stringent requirements of long cathode lifetime with high stability. Since the discovery of the excellent EFE properties of Q-carbon composite structure,[3] there has been a significant increase of interest in studying the emission stability of this material for practical device applications. The carbon-based field emitters such as carbon nanotubes, diamond, nano-diamond, and diamond-like carbon (DLC), have been investigated, however, reliable commercial devices such as field emission lighting elements, frictionless motors, flat panel displays, etc. are still challenging to develop due to several barriers.[4] Over the decades, diamond has been considered as one of the most promising materials for cold-cathode applications owing to its negative electron affinity (NEA).[5,6] However, the ideal single crystal diamond cannot provide the required amount of electrons for the field emission, and the band structure of diamond is unsuitable for the transport of those electrons to the surface. Usually, the diamond surface is terminated by hydrogen to obtain NEA for enhanced EFE properties. But exposing the hydrogen-terminated diamond surface to high fields and to oxygen ambient for several days is enough to replace some of the surface hydrogen with different oxygen groups. This diminishes the NEA and thereby reduces the percentage of the emitting surface area, and worsens the EFE performance.[7] Therefore, researchers have tried nanometer size or highly defective crystallites having much degraded physical properties than the crystalline diamond, such as polycrystalline diamond, nitrogen-incorporated ultrananocrystalline
diamond, and DLC.[8–11] The EFE characteristics from the DLC and amorphous carbon can be compared with vacuum breakd
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