A screen printed carbon nanotube-based field emission device

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonField emission devices have the potential to replace thermionic cathode electron sources in x-ray scanners and microwave devices. This study aims to exploit the high aspect ratio, small size and ballistic conductivity of carbon nanotubes (CNTs) to produce a field emission cathode with high current density and low turn-on field. A method of screen-printing CNT-containing inks has been developed and used to fabricate field emission cathodes on a variety of substrates. Increases in emission current density have been achieved by optimisation of CNT concentration and selection of CNT species. The device has the advantage over thermionic cathodes of requiring fewer connections, has no warm-up time and can be fabricated on several substrate materials. Additionally, a test setup has been developed to evaluate the performance of field emission devices capable of delivering high current densities in a diode configuration, featuring an adjustable anode-cathode gap, a current limiting resistor and the option of a phosphor-coated glass anode to assess emitter uniformity.UK Engineering and Physical Sciences Research Council, TMD Technologies Lt