Morphology of crystalline nitrogenated carbon films prepared by HF-CVD

A hot filament chemical vapour deposition (HF-CVD) process has been used fo r fabrication of crystalline nitrogenated carbon (C:N) films without hydrog en additions. Decomposition of methane (CH4) in nitrogen (N-2) atmosphere r esults in a new type of him growth characterised by various polymorphs incl uding worm- or needle-like microstructures. Therefore these films show a la rge surface area. Under certain deposition conditions thigh filament and su bstrate temperature, small distance, r, between filament and substrate) ver y high deposition rates up to 2000 nm/min were achieved and the formation o f a cauliflower structure was observed. Additionally coiled carbon fibres a nd chains of nanobeads were produced which shape, diameter and length depen d on the lateral distance from the filament. These tubular structures show an interesting feathered surface. The structure and the chemical compositio n of the deposited C:N films were studied by scanning electron microscopy ( SEM), transmission electron microscopy (TEM), and electron energy loss spec troscopy (EELS). The crystallinity of the films is derived from the lattice planes clearly seen in high resolution (HR) TEM. By Raman spectroscopy the vibrational properties were observed showing a disordered graphitic-like s tructure. (C) 2000 Elsevier Science B.V. All rights reserved.