Enhanced Photocurrent in GeSi NCs / TiO2Multilayers

Abstract

GeSi NCs / Ti02 multilayers with enhanced photocurrent properties were prepared and studied. Multilayers of Ti02 /(GeSi/Ti02)x2 /Si-p were deposited by magnetron sputtering and annealed by RTA at 700 °C for GeSi NCs formation. A post-annealing hydrogenation in plasma was performed on multilayers for healing of defects acting as traps and/or recombination centers and consequently producing the photocurrent enhancement. We studied the electrical and photoconductive properties of multilayers annealed by RTA and post-annealing hydrogenated. The current - temperature dependence reveals the conduction mechanisms in GeSi NCs / Ti02 multilayers RTA annealed, i.e. thermal activation of carriers to extended states (0.31 eV activation energy), the electron tunneling mechanism to nearest neighbors (T-1/2 behavior) and Mott variable range hopping (T−1/4 dependence). The photocurrent spectra made on multilayers structures hydrogenated for 10, 20 and 30 min evidence the photocurrent increasing up to 50%, showing that the hydrogenation is a suitable treatment for enhancing photocurrent. All photocurrent spectra present a dominant maximum (920 nm) and two shoulders (~770 and~ 10 60 nm).