Enhancement of the stability of electron field emission behavior and the related microplasma devices of carbon nanotubes by coating diamond films.

Abstract

The enhanced lifetime stability for the carbon nanotubes (CNTs) by coating hybrid granular structured diamond (HiD) films on Au-decorated CNTs/Si using a two-step microwave plasma enhanced chemical vapor deposition process was reported. Electron field emission (EFE) properties of HiD/Au/CNTs emitters show a low turn-on field (E0) of 3.50 V/μm and a high emission current density (Je) of 0.64 mA/cm(2) at an applied field of 5.0 V/μm. There is no notable current degradation or fluctuation over a period of τ(HiD/Au/CNTs) = 360 min for HiD/CNTs EFE emitters tested under a constant current of 4.5 μA. The robustness of the HiD/CNTs EFE emitter is overwhelmingly superior to that of bare CNTs EFE emitters (τ(CNTs) = 30 min), even though the HiD/Au/CNTs do not show the same good EFE properties as CNTs, which are E0 = 0.73 V/μm and Je = 1.10 mA/cm(2) at 1.05 V/μm. Furthermore, the plasma illumination (PI) property of a parallel-plate microplasma device fabricated using the HiD/Au/CNTs as a cathode shows a high Ar plasma current density of 1.76 mA/cm(2) at an applied field of 5600 V/cm with a lifetime of plasma stability of about 209 min, which is markedly better than the devices utilizing bare CNTs as a cathode. The CNT emitters coated with diamond films possessing marvelous EFE and PI properties with improved lifetime stability have great potential for the applications as cathodes in flat-panel displays and microplasma display devices.