the have been ascribed to the sharp tips of the non aligned grass-like
nanostructured leaves which cause the strong screening effects.
Other factors which can affect the field emission properties are tip radius
of the emitters, density of emitters, aspect ratio, morphology, intrinsic
properties and dimensions of the emitters etc. [9].
The behavior of the emission current density (J) versus the applied
electric field (E) was analyzed using the Fowler-Nordheim (FN) equation
[14] which can be expressed as