Interfacial potential and photoelectronic properties of manganite heterojunction La0.7Ce0.3MnO3/SrTiO3:Nb

The interfacial potential and photoelectronic properties of a heterojunction composed of La0.7Ce0.3MnO3 and SrTiO3:Nb have been experimentally studied. A two-dimensional spatial distribution of the electrostatic potential across the La0.7Ce0.3MnO3∕SrTiO3:Nb interface is obtained by the holography technique of the transmission electron microscope, which reveals the presence of a depletion layer of 8 nm in thickness at 120 K and 3 nm at 296 K and a built-in electric field within this layer. Consequently, a complex yet significant photovoltaic effect is observed. It is found that the transient photocurrent is composed of two distinctive processes with the charging-like behavior, and the time constants are surprisingly larger than that expected for a photoelectronic process, ∼30 and ∼260μs, respectively. It seems to be an intrinsic property of the manganite junction, and has nothing to do with external circuit and thermolelectric effect arising from light illumination.