Enhancement of electron emission efficiency of Mo tips by diamondlike carbon coatings

Abstract

The effect of diamondlike carbon (DLC) films coated by pulsed laser deposition technique on the electron emission characteristics of Mo tips is examined. Turn-on voltage (V0) was lowered from 40 V for Mo tips to 22 V for DLC coated Mo tips and maximum anode current (IA) was increased from ∼44 μA for Mo tips to ∼2.0 mA for DLC coated Mo tips. Maximum anode current (IA) for the DLC coated Mo tips, however, decreased during operation. Raman spectroscopy and selected area diffraction (SAD) in transmission electron microscopy (TEM) revealed that the degradation of electron emission behavior can be ascribed to the conversion of sp3-bonds, characteristic for diamond, to sp2-bonds, characteristics for graphite. The transformation of the structure is assumed to be induced by the local heat from the DLC coatings.

Carbon cone arrays by double-bias assisted hot filament plasma chemical vapor deposition

“…Due to super hardness and chemical inertness, the surfaces of diamond/DLC films are difficult to be modified, and the cones were conventionally fabricated via depositions in the inverted holes pre-patterned on the substrates [4,12], or on silicon, tungsten, and molybdenum tips [13][14][15], which had already been found to enhance effectively the emission properties. However, those approaches involve complex procedures, and also depend strongly on the micro-fabrication techniques such as photolithography, reactive ion etching, and wet etching.…”

Electron field emission and surface morphology of a-C and a-C:H thin films

“…The coefficient b, determined from the slope of straight lines in Fig. 1, was found to be similar (between 70 and 120) for the three types of carbon films investigated (assuming that u=1.5 eV [11]). On the basis of these data, the curvature radius of emitting centers can be assumed to be similar for the three types of samples.…”

Electron field emission characteristics of planar diamond film array synthesized by chemical vapor deposition process

“…The planar diamond film array described above possesses the same order of emission current density as that of the diamond coated Mo tip 19 array. However, in diamond coated tip array, only the grains sitting on top of the tips are responsible for electron field emission.…”

“…However, in diamond coated tip array, only the grains sitting on top of the tips are responsible for electron field emission. Those diamond grains degraded rapidly due to thermal instability, 19 since the current density which flew through them is enormously large. By contrast, each grain in the planar array shares only a small fraction of emission current that significantly reduces the degradation of diamonds.…”