Electrochemical characterization on semiconductors p-type CVD diamond electrodes

Abstract

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-1 decreases 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 of μA 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 Ufb 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 1018 and 1021 cm-3. These values agree with the estimated concentration obtained by Raman measurements.