Field emissionmeasurements of grass-like leaveswere performed in
a vacuum chamber with a pressure of 1.2×10−6 Pa at room temperature.
A rod-like stainless steel probe (1mm in diameter) of 0.78mm2
in area was used as an anode and product was used as cathode. The
spacing between these two electrodes was 200 μm. By definition, the
turn-on field is the electric fields required to produce emission current
density of 0.01 mA cm−2 where as threshold fields is the electric fields
required to produce emission current density of 1 mA cm−2 [9].