Field emission arrays from graphite fabricated by laser micromachining

Laser microstructuring allows the manufacturing of conical shaped emitters on a graphitized carbon substrate without any additional treatment. Integral field emission measurements were performed in a diode configuration with a 50 μm mica spacer and a metalized Si-grid in a vacuum chamber at pressures of about 10⁻⁹ mbar. Emission currents up to 10 μA at a voltage of 1000 V (11 MV/m) with a positive current drift were observed for an array of 16 emitters. A strong modification of the emitter tip is noticeable after individual measurements. A comparable alteration of the surface is also achieved by an electrochemical treatment of the samples with a potassium hydroxide solution. However, the IV-measurements of such samples show not only higher onset voltages but also higher integral emission currents. For all arrays, an ideal Fowler–Nordheim (FN) behavior is only noticeable at applied voltages below 625 V (7 MV/m). Numerical calculations indicate that the deviation in the FN-plot for higher voltage values is caused by the change of the effective work function.