Direct observation of sp(3) bonding in tetrahedral amorphous carbon using ultraviolet Raman spectroscopy

The vibrational modes of the sp(3) sites in tetrahedral amorphous carbon (ta-C) thin films are revealed directly using ultraviolet Raman spectroscopy at 244 nm excitation and are shown to produce a Raman peak centered around 1100 cm(-1). In addition, the main Raman peak associated with sp(2) vibrational modes is shifted upward in frequency by 100 cm(-1) relative to its position in spectra excited at 514 nm. The spectra are interpreted in terms of the bonding in ta-C. (C) 1997 American Institute of Physics.