Among all the allotropic forms of carbon, diamond has attracted a broad scientific and technological interest for its extreme and unique properties rarely matched by other materials in nature. In a rapid rise from a technological point of view, much has been achieved in the study of obtaining this material through CVD technique. Studies of CVD diamond growth parameters of monocrystalline structure, underway in the team, are very expensive and time-consuming requiring in-depth studies of CVD diamond growth parameters of polycrystalline structure. So, this work presents an analysis focused on obtaining CVD diamond films with polycrystalline structure through the 2.45 GHz microwave plasma activation method (MWPACVD) in high power regime using a modified substrate holder to find a set of parameters appropriated for getting uniform quality and growth rate of thick films. The films were characterized using Raman scattering spectroscopy and scanning electron microscopy. The results point to optimized conditions for depositing films with growth rates of up to 20 µm/h with low levels of intrinsic stress, good structural quality and uniform microcrystalline morphology along the deposition surface.

Semiconductor boron-doped CVD diamond films were prepared on Si substrates by the hot filament technique. The surface morphology analysis by SEM presented continuous and well faceted films. The samples were grown with different boron concentrations by controlling the B/C ratio in the feeding gas. Raman results showed a drastic change of diamond films for different doping levels. The characteristic line at 1332 cm-1decreases and shifts to lower energy as a function of the film resistivity. It was also observed a broad peak around 1220 cm-1 caused by the incorporation of boron in the diamond lattice. Photocurrent-voltage behaviour of undoped and boron-doped diamond electrodes was investigated in dark and UV visible irradiation. The voltammograms showed that doped electrodes illuminated with a xenon lamp exhibited currents significatively higher because of the increased conductivity. For undoped electrodes it was observed a small photocurrent for anodic and cathodic polarization in the order ofmuA for the potential range of +1.0 V and -1.0 V (Ag/AgCl), for 1.0 M KCl. Mott-Schottky plots studied the interfacial processes at diamond-electrolyte junction. The flatband potential Uf b was found between 0.6 and 0.8 V (Ag/AgCl) which varies with the presence of sp² -type carbon as an impurity. From the curve slope the acceptor concentrations were found in the range of 10(18) and 10(21) cm-3 .These values agree with the estimated concentration obtained by Raman measurements.