Carbon fibre production during hydrogen plasma etching of diamond films

Diamond thin films have showed outstanding performance when exposed to extreme conditions such as high power plasmas. However there are always concerns about the stability of the diamond structure in the presence of other materials deposited on the film surface by plasma diffusion. It is known that diamond films are etched by hydrogen plasma but in the presence of Si, carbon fibres are formed. In this report we show for the first time the effect of Si on the production of fibres under etching conditions and propose growth mechanisms based on the results of characterisation techniques. Carbon fibres have been synthesised on diamond films and characterised by scanning electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. In situ optical emission spectroscopy was performed during the experiments showing different concentration of growing species which may result in the observed variability of fibres growth rate and morphology. Furthermore, fibres varied in size and shape depending on the structure of the diamond films. The surfaces of the fibres contain silicon and are oxidised having COO and CO groups as seen by XPS analysis. Raman analyses revealed a spectrum typical for graphite combined with that from diamond that remains on the surface after hydrogen bombardment. The results of this study show the experimental conditions in which carbon fibres are produced under high hydrogen etching of diamond films and opens the possibility to other applications such as catalysis, sensors and the production of electrodes, since they combine the unmatchable properties of a diamond supporting substrate with the unique properties of carbon fibres.