Low voltage electron emission from calcium carbonate whiskers coated with a thin layer of gold

Cold cathode electron field emission from aragonite CaCO3 whiskers coated with 10-nm-thick gold has been observed. The microstructure of the whiskers grown on a Ni substrate by electrochemical deposition has been examined by scanning electron microscope, energy dispersive x-ray spectrometer, x-ray diffraction spectrometer, and Raman spectroscopy. For a 220 μm anode-cathode gap, emission current densities in excess of ∼2×10−6 A/cm2 are observed for applied voltages of 660 V or greater. Although it is believed that the electric field is locally enhanced by the geometry of the whiskers, the voltage required increases roughly linearly with the anode-cathode spacing, corresponding to a turn-on field of approximately 3 V/μm, and an emission current density of 0.4 mA/cm2 has been obtained for an applied field of 5.5 V/μm.