Field emission measurements with micrometre resolution on carbon nanostructures

The field emission properties of carbon nanostructures grown in a microwave plasma chemical vapour deposition system under bias conditions were invest igated. Different carbon nanostructures, namely nanocrystalline diamond fil ms (sample A) and nanotubes (sample B), were grown under conditions similar to those employed during the bias pretreatment for diamond growth. Morphol ogical and structural properties of the carbon nanostructures were investig ated by scanning electron microscopy, Raman and photoelectron spectroscopy. The field emission properties of the samples were measured by means of a f ield emission scanning microscope using resolutions of 3 and 40 mu m, respe ctively. 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 t o an improved emission behaviour, while on sample B the application of high er currents can be detrimental in some cases. The average onset field stren gth (measured at a current of 0.5 nA) was as low as 55 V/mu m (sample A) an d 9 V/mu m (sample B), respectively, compared with 200 V/mu m and more for CVD diamond films. (C) 1999 Elsevier Science S.A. All rights reserved.