Photovoltaic effect in the La_(0.67)Ca_(0.33)MnO_3/LaMnO_3/SrTiO_3:Nb heterojunctions with variant LaMnO_3 layers

摘要

Influence of LaMnO_3 layer, 0-12 nm in thickness, on photovoltaic effect (PVE) has been experimentally studied for the La_(0.67)Ca_(0.33)MnO_3/SrTiO_3:Nb junction. Presence of LaMnO3 causes an obvious weakening of the PVE, demonstrated by the reduction in the carrier density excited by each photon. The interfacial barrier deduced from the PVE shows a rapid growth, from ～1.22 to～ 1.45 eV, as the layer thickness increases from 0 to 2 nm, and saturates at ～1.5 eV above 2 nm. On the contrary, current-voltage characteristics suggest a smooth reduction in interfacial barrier with layer thickness. These results can be quantitatively understood assuming the occurrence of a notch and a spike in the conduction band edges at the interface of the junction.