Instability of hydrogenated amorphous carbon films towards defect creation at high disorder

We report a complete characterization of hydrogenated amorphous carbon (a-C:H) thin films through Raman spectroscopy, photothermal deflection spectroscopy, and mechanical studies. The interpretation of the optical absorption data within the Dasgupta’s model offers an estimate of the disorder intensity through a characteristic energy scale of the model. The vibrational data (Raman spectra) and the stress data together with the optical absorption data give strong evidence for a sharp transition between a low disorder state dominated by aromatic rings and a strong disorder state likely in keeping with the creation of some topological defects, such as odd rings.