The spatial coexistence of magnetic and ferroelectric domains in multiferroic BiFe0.96Co0.04O3 film is confirmed by multimode scanning probe microscopy. The applied bias dependence of the surface potential in BiFe0.96Co0.04O3 indicates that surface potential is determined by the interplay of polarization and surface charges. It is also shown that multiferroic BiFe0.96Co0.04O3 can more easily trap surface charges than the well-known ferroelectric PbZr0.53Ti0.47O3. The time evolution of surface potential exhibits an exponential decay, which is closely related to the observed spread of surface charges. The study on BiFe0.96Co0.04O3 unveils the origin and evolution behavior of the surface potential in BiFeO3-based multiferroic films.

We report a bistable resistance switching behavior of CuO thin films. To understand the resistance switching mechanism, we have studied impedance spectroscopy and nanoscale electrical property. From the frequency-dependent impedance properties of CuO thin films in high resistance (ROFF) and low resistance (RON) states, we infer the formation of conducting paths generated by external bias as a possible origin of the bistable resistance states. In addition, the observation of inhomogeneous conducting path using a conducting atomic force microscope is also consistent with our inference.

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We report a bistable resistance switching effect in amorphous InGaZnO (a-IGZO) thin films deposited by a pulsed laser deposition method. The electrical properties of a-IGZO thin films were controlled by the oxygen partial pressure during deposition and this determined the resistance switching effect. We also observed the resistance switching effect with various electrodes such as Pt, Au, and Al. We suggest that the resistance switching effect is related to the formation of a conducting path by metal and/or oxygen vacancy defects in the a-IGZO matrix.