The mystery of the 1140 cm(-1) Raman line in nanocrystalline diamond films

A strong and distinct Raman peak around 1140 cm(-1) is often taken as a simple criterion for a nanocrystalline diamond phase in deposited diamond films. However, the observation that (i) this mode is always accompanied by a mode around 1480 cm(-1) (seen around 1490 cm(-1) as a shoulder of the G-mode), (ii) both of these modes show (similar) dispersions while the diamond mode around 1332 cm(-1) does not, and (iii) these both modes vanish after thermal annealing but the diamond mode not, made this assignment doubtful. By performing a thin film preparation with deuterium and H-D substituted hydrocarbon sources we provide direct evidence that these two modes originate from trans-polyacetylene in the diamond film. (C) 2004 Elsevier Ltd. All rights reserved.