Origin of ultraviolet photovoltaic effect in Fe3O4 thin films

摘要

We have investigated the transport and ultraviolet photovoltaic properties of Fe3O4 thin films grown on glass substrates by facing-target sputtering technique. The nonlinear dependence of current-density on voltage suggests that the transport process is most likely the tunnelling process and grain boundaries act as barriers. Furthermore,nonequilibrium electron-hole pairs are excited in the grains and grain boundary regions for Fe3O4 film under ultraviolet laser, since the energy gap of Fe3O4 is smaller than the ultraviolet photon energy. And then the built-in electric field near the grain boundaries will separate carriers, leading to the appearance of an instant photovoltage.