Si-doped and nanocomposite Si-diamond films: cathodoluminescence and ohotoluminescence characterizations of Si centers

technique. These films are of great interest for optoelectronic applications, but it has been experienced that the structural and optical properties of such composite materials depend dramatically on both concentration and distribution of Si defects. In this work Micro-Raman spectroscopy, Scanning Electron Microscopy (SEM), Photoluminescence (PL), and Cathodoluminescence (CL) techniques have been employed to explore the 1.68 eV Si-related centers in polycrystalline CVD diamond films. The spatial distribution of these defects inside the diamond lattice has been studied by performing a series of CL, PL and Raman mapping with a sub- and micrometric resolution. The results allowed to correlate the emission features with the crystallographic orientation, evidencing more intense luminescence signals from (100) faces of diamond crystallites. As regards the Si distribution, the PL analysis evidenced that Si centers are preferentially located in proximity of the dislocations in the diamond crystal lattice. Moreover, the Raman signal shift of diamond peak position indicates that the Si centers give rise to a slight compressive stress, dependent on the Si concentration. Overall, the investigations carried out confirm that this CVD approach affords versatility with regards the insertion of Si centers inside the diamond lattice together with the insertion of Si nanoparticles in the diamond matrix and is suitable for production of purpose-designed optical layers.