Nanocomposite Si/diamond layers: room temperature visible-light emitting systems

Visible-light emitting nanocomposite Si/diamond polycrystalline layers, produced by means of a hybrid CVD/powder-flowing technique, have been investigated by atomic force microscopy (AFM),reflection high energy electron diffraction (RHEED), Raman spectroscopy, photoluminescence(PL), and electron spin resonance (ESR). The room temperature emission of the layers at 1.7 eV and 2.0-2.4 eV is dominated by the optical properties of the inserted Si nanoparticles (mean diameter 3.3 +/- 0.5 nm). The density of the ESR active centers is N = (4 +/- 2) x 10(19) cm(-3) with g = 2.0025 (T = 300 K). A study of the temperature-dependent changes in the nature and localization of paramagnetic centers has been carried out by comparing the ESR signals taken at 300 K, 30 K, and 4.2 K. The ESR results suggest that the active centers originate from the dangling bonds induced in sp(3)-coordinated C atoms by insertion of the Si nanoparticles. The g-factor anisotropy, detected at 4.2 K, is consistent with the peculiarities of dipole-dipole interactions in structures with low dimensionality.