Electric-field-induced resistance behavior in Ag/Pr1-x Cax MnO3/Pt (x=0,0.3,1.0) heterostructures

The resistance behaviors of three kinds of heterostructures, Ag/Pr1-xCaxMnO3/Pt (Ca doping level x=0,0.3,1.0), were investigated under electric excitation. It was found that there are huge differences in the resistance behaviours of the Ag/Pr1-xCaxMnO3/Pt heterostructures depending on the Ca doping level. The resistance of Ag/PrMnO3/Pt (x=0) decreased all along with increasing pulse voltage until breakdown. Ag/Pr0.7Ca0.3MnO3/Pt (x=0.3) showed resistance switching with a large resistance change ratio and better switching stability. For Ag/CaMnO3/Pt (x=1.0), after the initial resistance fluctuation, the resistance jumped up to a high level until breakdown. The I-V characteristics of the three structures exhibited different carrier conduction processes. For Ag/PrMnO3/Pt, the carriers were in a strong-trapping state with a weak-detrapping process related to the LRS (low-resistance state). For Ag/Pr0.7Ca0.3MnO3/Pt, the carriers' transport with a strong-trapping/detrapping process is related to the resistance switching between HRS (high-resistance state) and LRS. For Ag/CaMnO3/Pt, the carriers were in a weak-trapping/detrapping process related to the HRS. Furthermore, the dependences of the I-V characteristics on the sweep rate and temperature for the three kinds heterostructures were also studied. In the consideration of the distribution of Mn3+ and Mn4+ ions in Pr1-xCaxMnO3 and the electronic configuration of Mn3+ and Mn4+ ions, it is suggested that the coexistence of Mn3+ and Mn4+ ions together with the O2- ion is the origin of polarity-dependent resistance switching in the Ag/Pr0.7Ca0.3MnO3/Pt heterostructure; the itinerant electron existing in Mn3+ ions is responsible for the polarity-independent resistance decreasing in Ag/PrMnO3/Pt heterostructure; the absence of mobile electrons in Mn4+ ions is responsible for the high resistance level in the Ag/CaMnO3/Pt heterostructure. (orig.)