Raman characteristics and intrinsic stress of tetrahedral amorphous carbon films with different film thicknesses

To investigate the effects of film thickness on Raman characteristics and intrinsic stress of tetrahedral amorphous carbon (ta-C) and to ascertain the correlations between stress and Raman spectra, ta-C films with different film thickness were deposited on a polished P-type ( 100) monocrystalline silicon substrate by a filtered cathodic vacuum arc technology. The film thickness was measured by a surface profiler and AFM, and stress was calculated according to the curvature of samples examined by the surface profiler while the microstructure of the films was characterized by Raman spectra. It is found that the stress drops continuously and then levels off with the increase of film thickness. When the film thickness exceeds 30 nm, the compressive stress is less than 5 GPa. The intensity of the first and second order peak of the monocrystalline silicon substrate in the Raman spectra gradually decreases with the increase of thickness. For film thicknesses from 50 nm to 80 nm, the full width at half maximum of the peak is a minimum, the intensity of the peak is a maximum, and the clearest Raman signals can be acquired. Additionally, the position of the broad peak gradually shifts to a lower wave number with the increase of thickness and the decease of intrinsic stress.