Tailoring the diameter of decorated C–N nanotubes by temperature variations using HF-CVD Original Research Article

Patterned films of decorated nitrogenated carbon (C–N) nanotubes were catalytically synthesised by hot filament chemical vapour deposition (HF-CVD) in a nitrogen–methane–ammonia environment. The systematic study of a transition between different kinds of C–N nanostructures as a function of the local substrate temperature ranging from 700 up to 820°C is presented. The morphology, the diameter as well as the properties of the generated tubular structures showed strong dependence on this parameter. By means of electron microscopy a new type of decoration covering all tubular structures was observed. Buckled lattice fringes revealed the disordered graphitic-like character of the hollow C–N nanotubes. Raman spectroscopy confirmed a transition in the microscopic order as a function of temperature. Furthermore field emission in vacuum was studied and showed a spectacular correlation to the deposition temperature and therefore the diameter of the C–N tubes. For arrays of tubes thinner than 50 nm an onset field below 4 V/μm was observed.