Characterisation of Diamond-like Carbon by Raman Spectroscopy and Optical Constants

Abstract

AbstractCrystalline diamond coatings and, increasingly, diamond like amorphous carbon (DLC) films are used for tribological and protective layers for their hardness and chemical inertness. They are also under investigation for their electron emitting properties, with possible applications in field emission displays. DLC films were deposited by laser ablation using a KrF excimer laser and fluences between 0.5 and 2 J/cm2. FTIR measurements did not show the presence of hydrogen in the films. Raman spectra allowed for the determination of the nature of the graphitic and diamond bonds (sp2 and sp3) as well as information about the disorder and short range order in the films. For a better determination of the sp3-content, which is often hidden in the Raman spectra, a correlation with optical properties in the near IR to near UV region was established. These values depended strongly on the substrate temperature and the laser fluence. DLC formation could be demonstrated even at substrate temperatures close to room temperature. Vickers hardness values and first measurements on the electron emissivity of the films can be correlated to the diamond character and the preparation method of the films.