Synthesis and characterization of diamond based systems for optoelectronic and biomedical applications

Thanks to the financial support of FBK Institute, the PhD program was aimed at the study of the electrical and optical properties of synthetic diamond containing impurities that behave as charge carriers or optically active defects. Polycrystalline diamond (PCD) films hosting Silicon-Vacancy ( ) and Si-Ni complexes color centers were produced on Si substrates coated by Ni by means of Hot Filament Chemical Vapor Deposition (HFCVD) technique. The Ni was deposited by both chemical and physical methods and the effects of Ni on the morphological, structural and surface features of the diamond systems were investigated as a function of substrate pretreatment, growth time, metal amount, etc. The involvement of Ni during the synthetic process supports the introduction of and Si-Ni color centers into the diamond matrix, providing a multi-wavelength emission, as evidenced by PL measurements. Moreover, the incorporation of Ni-related species gives diamond samples appealing electrical conductivity. Such conductive diamond characterized by more than one ZPL are therefore applicable in many advanced opto-electronic technologies. Noticeable charge transport properties were also found for Ti-doped PCD layers, grown on Titanium substrates and doped directly during the synthesis by gas phase reactions. Once the combination of surface polishing method of Ti substrates and the suitable synthetic process duration necessary to produce continuous, well-adhered good quality diamond coatings were disclosed, the effects induced by the Ti-doping on surface topography, chemistry, conductivity and biocompatibility of PCD layers were investigated. Ciclovoltammetry (CV) measurements showed that the materials assembled with Ti-doped diamond films behave as electrodes able to operate in harsh environments. For the assessment of the biocompatibility performance, MG-63 cell lines (Homo sapiens bone osteosarcoma) were cultured on various Ti-doped and undoped diamond samples. It was found that the incorporation of Ti entities into the lattice confers surface features suitable for cells adhesion and proliferation. These findings boost the interest to produce a conductive and biocompatible material that not only represents a promising scaffold for tissue engineering, but also opens the way to the fabrication of diagnostic and bio-stimulating innovative devices.