Voltage bias induced modification of the transport property of all oxide Pr_0.5Ca_0.5MnO₃/SrTi_0.95Nb_0.05O₃ junctions

Abstract

In this paper we report what happens to a virgin oxide junction Pr_0.5Ca_0.5MnO₃/SrTi_0.95Nb_0.05 O₃ (PCMO/Nb:STO), when it is subjected to cycling of voltage bias of moderate value (±4 V). It is found that the initial cycling leads to formation of a permanent state of lower resistance where the lower resistance arises predominantly due to the development of a shunt across the device film (PCMO). On successive voltage cycling with increasing magnitude, this state transforms into states of successive lower resistance that can be transformed back to the initial stable state on cycling to below a certain bias. A simple model based on p-n junction with shunt has been used to obtain information on the change of the junction on voltage cycling. It has been shown that the observation can be explained if the voltage cycling leads to lowering of the barrier at the interface and also reduction in series resistance. It is suggested that this lowering can be related to the migration of oxygen ions, which causes the vacancies at the junction region. Cross-sectional imaging of the junction shows formation of permanent filamentary bridges across the thickness of the PCMO after the virgin p-n junction is first taken through a voltage cycle, which would explain the appearance of a finite shunt across the p-n junction.