Influence of the dynamic lattice strain on the transport behavior of oxide heterojunctions

摘要

All-perovskite oxide heterojunctions composed of electron-doped titanate La_xSr_(1-X)TiO_3 (x = 0.1, 0.15) and hole-doped manganite La_(0.67)Ca_(0.33)MnO_3 films were fabricated on piezoelectric substrate of (001)-0.7Pb(Mg_(1/3)Nb_(2/3))O_3-0.3PbTiO_3 (PMN-PT). Taking advantage of the excellent converse piezoelectric effect of PMN-PT, we investigated the influence of the dynamic lattice strain on transport properties of the heterojunctions by applying external bias electric fields on the PMN-PT substrate. Photovoltaic experiments were carried out to characterize the interfacial barrier of the heterojunction. A linear reduction in the barrier height was observed with the increase of the bias field applied on PMN-PT. The value of the barrier height reduces from ～1.55 (～1.30) to 1.02 (1.08) eV as the bias field increases from 0 to 12kV/cm for the junction of La_(0.10)Sr_(0.9)TiO_3/La_(0.67)Ca_(0.33)MnO_3 (La_(0.15)Sr_(0.85)TiO_3/La_(0.67)Ca_(0.33)MnO_3). The observed dependency of barrier height on external field can be ascribed to the increasing release of trapped carriers by strain modulation, which results in a suppression of the depletion layer and increases the opportunity for electron tunneling across the depletion area.