New forms of hydrogen-free amorphous carbon films Original Research Article

Amorphous carbon films free of hydrogen, deposited at room temperature by magnetron sputtering, were found to exhibit amorphous diamond character. The films were studied during deposition with real time and in situ spectroscopic ellipsometry (SE), from which the transparency, spectral dependence and composition were determined. Raman spectroscopy and X-ray reflectivity were also used to investigate the film type, bonding formation and density. In addition, stress measurements conducted with the cantilever technique prove that the internal stresses in the films are compressive and above 4 GPa. The results from the above techniques show that films rich in sp3 CC bonds are dense, highly stressed and metastable. These films do not exhibit in Raman spectra the characteristic G and D bands of DLC films, but instead a new band appears at about 1120 cm−1. This band disappears when the spectra are recorded with higher laser intensities and the film undergoes a phase transformation. Electron diffraction patterns obtained from specimens after chemical etching reveal amorphous highly deformed sp2 and sp3 CC sites, whereas the same specimens prepared with Ar ion bombardment exhibit polycrystalline diamond structure.