A novel semi-metallic allotrope of carbon

A previously unknown allotrope of 3-dimensional crystalline carbon has been synthesized via CVD. Formation occurs when specific hydrocarbons react with certain metal or metal-oxide catalysts such as copper or aluminum oxide at temperatures above 800°C. The material has been characterized by XRD, Raman, FTIR and XPS. Raman spectra indicate the material consists of a mixture of sp₂ and sp₃ bonded carbon. X-ray diffraction shows distinct peaks which do not correlate with graphite or diamond. Upon annealing at 1,100°C the diffraction peaks show considerable sharpening indicating the formation of larger domains. This is also reflected in the Raman spectrum which also shows a sharpening of the D and G carbon peaks. XPS analysis did not indicate the presence of any element beside carbon. The material has a high reflectivity from far UV to mid IR and visually appears mirror-like when deposited on smooth substrates. The temperature dependent conducitvity has a negative temperature coefficient suggesting the material is most likely a semi-metal as opposed to a true metal; something not unexpected with carbon.