Spectroscopic characterization of carbon chains in nanostructured tetrahedral carbon films synthesized by femtosecond pulsed laser deposition

摘要

A comparative study of carbon bonding states and Raman spectra is reported for amorphous diamondlike carbon films deposited using 120 fs and 30 ns pulsed laser ablation of graphite.The presence of sp1 chains in femtosecond carbon films is confirmed by the appearance of a broad excitation band at 2000-2200 cm-1 in UV-Raman spectra.Analysis of Raman spectra indicates that the concentrations of sp1-,sp2-,and sp3-bonded carbon are approx=6%,approx=43%,and approx=51%,respectively,in carbon films prepared by femtosecond laser ablation.Using surface enhanced Raman spectroscopy,specific vibrational frequencies associated with polycumulene,polyyne,and trans-polyacetylene chains have been identified.The present study provides further insight into the composition and structure of tetrahedral carbon films containing both sp2 clusters and sp1 chains.