Ultraviolet and visible Raman spectroscopy characterization of diamond-like carbon film growth by pulsed laser deposition

Diamond-like carbon (DLC) films were prepared by pulsed laser deposition at various substrate temperatures. These films have been studied using ultraviolet (UV, 244 nm) and visible (514 nm) micro-Raman scattering. The Raman characteristics and structural changes in the films are found as a function of deposition temperature. The total sp³ fraction in the film remains almost constant at a temperature not greater than 200 °C and shows a sharp decrease at a temperature greater than 200 °C. In the visible Raman spectra, only vibrational modes of sp²-bonded carbon (G and D peaks) are observed. A wide peak, called the T peak, located at 1080-1260 cm^-1, associated with the vibrational mode of sp³-bonded carbon, appears in the UV Raman spectra from DLC films deposited at temperatures from 25 to 200 °C. In the visible Raman spectra, the G-peak width and the intensity ratio I(D)/I(G) are sensitive to the structural changes induced by the change of the deposition temperature. In the UV Raman spectra, both G peak and T peak positions are sensitive to these structural changes.