(Color online) (a) Top view SEM micrograph of a typical CNS cathode. The outboard edges terminate in one to seven graphene layers (average is three layers) and are ideal electron emission sites under an applied field. (b) A schematic cross section of a CNS film grown on a Si substrate. (c) A computational contrast analysis of the SEM micrograph in (a) highlighting topographical features furthest from the substrate that may better represent the actively etched area.
(Color online) Schematic of the UHV diode apparatus used for field emission testing and simultaneous reaction-product measurement by a RGA in line of sight to the gap in the parallel plate testing geometry.
(Color online) Analog RGA survey (not calibrated) before and during field emission testing at a total emission current of . Before testing the total pressure (ion gauge). During testing, clear increases in the , , CO, and signals can be observed (dashed line).
(Color online) By adjusting the applied field up to , a stepwise field emission current is observed. Simultaneous measurements by the RGA show a corresponding response in the hydrogen and methane products. Similar responses were observed for both CO and .
(Color online) behavior during field emission of CNS dot samples in a diode geometry. The inset shows the corresponding Fowler–Nordheim plot.
(Color online) Linear least mean square fits (dashed) of RGA data as a function of current with 95% confidence bounds (dotted). The inset shows a linear plot of the data points in the high current regime.
(Color online) Observed gas flow rates at total field emission current with a Cu anode and with a Au-coated anode. The background data are taken with no field emission and a total pressure of .
(Color online) Raman spectra of the CNS cathode before and after 300 h dc field emission testing in a diode configuration. The ratio is used as a gauge of the relative defect density in the film. After testing the ratio has increased from 0.57 to 0.81 indicating that ESD-generated ions and neutrals have significantly reacted with and created further defect sites in the CNS.
(Color online) SEM micrographs of CNS cross sections before and after dc field emission testing for 200 h at a current density of . A clear reduction in the mean height of the CNS corresponds to an etching rate of .
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