Field emission measurements with micrometre resolution on carbon nanostructures

Abstract The field emission properties of carbon nanostructures grown in a microwave plasma chemical vapour deposition system under bias conditions were investigated. Different carbon nanostructures, namely nanocrystalline diamond films (sample A) and nanotubes (sample B), were grown under conditions similar to those employed during the bias pretreatment for diamond growth. Morphological and structural properties of the carbon nanostructures were investigated by scanning electron microscopy, Raman and photoelectron spectroscopy. The field emission properties of the samples were measured by means of a field emission scanning microscope using resolutions of 3 and 40 μm, respectively. The local emission follows the Fowler–Nordheim law up to 1 mA/mm 2 (3 mA/mm 2 ) for sample A (sample B). Higher currents lead for sample A to an improved emission behaviour, while on sample B the application of higher currents can be detrimental in some cases. The average onset field strength (measured at a current of 0.5 nA) was as low as 55 V/μm (sample A) and 9 V/μm (sample B), respectively, compared with 200 V/μm and more for CVD diamond films.