Keywords: field emission, luminescent screen imaging, scanning microscopes, carbon nanotubes, cathodes
Field emission measurement techniques for the optimisation of carbon nanotube cathodes
We have developed advanced measurement techniques for the investigation of the field emission (FE) properties of high-technology materials. Flat samples up to 30 mm in diameter can be optimised either for strong or weak electron emission, i.e., cold FE cathodes operating at field levels below 10 V/μm or high-voltage vacuum devices preventing FE up to 200 V/μm. The integral measurement system with luminescent screen (IMLS) provides a quick overview of the microscopic distribution and long- and short-term stability of the emission current, and facilitates a controlled conditioning of cold cathode samples at various pressures. The field emission scanning microscope (FESM) is incorporated within a UHV surface analysis system and enables high-resolution emitter distributions and local FE investigations down to the nanoscale. Exemplary results on carbon nanotube samples will be given to demonstrate that the combination of both instruments yields a very effective means for an improved understanding and tailoring of materials for cold cathode applications.