Structure and field emission properties of decorated C/N nanotubes tuned by diameter variations

We demonstrate here the possibility of tuning the field emission of nanotube emitters. Plasma enhanced hot filament chemical vapour deposition (PE-HF-CVD) combined with micro-contact printing of catalysts was performed in order to deposit patterned films of nitrogenated carbon (C/N) nanotubes. The systematic study is presented for transition between different kinds of twisted nanostructures as a function of the local substrate temperature ranging from 700 up to 820 degreesC. The morphology, the diameter, as well as the properties of the synthesised tubular structures showed a strong dependence on this parameter. The diameter of the twisted C/N tubes can be easily adjusted in a large range starting from 1 mum down to approximately 15 nm. By means of electron microscopy an interesting decoration covering all tubular structures was observed. Buckled lattice fringes revealed the crystalline but disordered graphitic-like character of the hollow C/N nanotubes. Furthermore, field emission in vacuum was studied resulting in a spectacular correlation to the deposition temperature and therefore, the diameter of the C/N tubes. For arrays of nanotubes thinner than 50 nm an onset field below 3 V/mum was observed and a field amplification factor beta of 1200 was determined in that case. In addition, very good long-term stability and the up-scalability of the fabricated nanotubes make them interesting for applications. (C) 2001 Elsevier Science B.V. All rights reserved.