PHOTOLUMINESCENCE OF POLYMER-LIKE AMORPHOUS-CARBON FILMS GROWN IN DIFFERENT PLASMA REACTORS

The visible photoluminescence (PL) properties (emission and excitation spectra) of hydrogenated amorphous carbon (a-C:H) have been investiga ted for polymer-like thin films grown at low substrate temperature and small ion energies. For a large number of a-C:H films grown in three reactors (dual-mode plasma, radio frequency plasma and electron cyclot ron resonance plasma) the emission spectra appear as a sum of three pe aks with energies (a) 2.28 eV, (b) 2.65 eV and (c) 2.95 eV, being inde pendent of the excitation energy (3.54 eV or 4.13 eV). Their relative intensities depend on the growth parameters while their positions are almost independent. Preliminary picosecond time-resolved PL data indic ate a decrease of the decay time for increasing emission energies. A t wo-phase model of a-C:H is proposed to explain the PL excitation spect ra. (C) 1998 Elsevier Science B.V. All rights reserved.