An optical absorption and electron spin resonance study in hydrogenated amorphous carbon prepared by radio frequency sputtering

In this work, we investigated different hydrogenated amorphous carbon (a-C: H) films grown by radio frequency (RF) magnetron sputtering covering a larg e variety of films from polymer-like carbon (PLC) to diamond-like carbon (D LC). Photothermal deflection spectroscopy (PDS), transmission spectroscopy in the visible and near infrared (IR) region were combined ir with electron spin resonance (ESR) measurements. The optical absorption spectra were ana lysed assuming a distribution of two overlapping Gaussian bands near the Fe rmi lever in order to deduce the density of states (DOS) at the Fermi level . From the DOS and the density of paramagnetic states a correlation energy for midgap states is derived. (C) 2000 Elsevier Science S.A. All rights res erved.