We report a unipolar, nonvolatile resistive switching in polycrystalline YMnO₃ thin films grown by pulsed laser deposition and sandwiched between Au top and Ti/Pt bottom electrodes. The ratio of the resistance in the OFF and ON state is larger than 10³. The observed phenomena can be attributed to the formation and rupture of conductive filaments within the multiferroic YMnO₃ film. The generation of conductive paths under applied electric field is discussed in terms of the presence of grain boundaries and charged domain walls inherently formed in hexagonal YMnO₃. Our findings suggest that engineering of the ferroelectric domains might be a promising route for designing and fabrication of novel resistive switching devices.

We report unipolar resistive switching in polycrystalline, hexagonal yttrium manganite thin films grown on unpatterned Pt metal coated SiO₂/Si substrates with circular Al top electrodes. Electroforming-free or electroforming-based resistive switching is observed, depending on the chemical composition (Y₁Mn₁O₃, Y_0.95Mn_1.05O₃, Y₁Mn_0.99Ti_0.01O₃, and Y_0.94Mn_1.05Ti_0.01O₃). The number of loading cycles measured at room temperature for samples with Y₁Mn₁O₃ and Y_0.95Mn_1.05O₃ composition is larger than 10³. The dominant conduction mechanism of the metal–insulator–metal structures between 295 K and 373 K in the high resistance state is space charge limited conduction and in the low resistance state is ohmic conduction. Activation energies in Ohm's law region in the high resistance state are calculated from the Arrhenius equation and are evaluated to be 0.39 ± 0.01 eV (Y₁Mn₁O₃), 0.43 ± 0.01 eV (Y_0.95Mn_1.05O₃), 0.34 ± 0.01 eV (Y₁Mn_0.99Ti_0.01O₃), and 0.38 ± 0.02 eV (Y_0.94Mn_1.05Ti_0.01O₃).

We have investigated ferroelectric charged domains in polycrystalline hexagonal yttrium manganite thin films (Y₁Mn₁O₃, Y_0.95Mn_1.05O₃, Y₁Mn_0.99Ti_0.01O₃, and Y_0.94Mn_1.05Ti_0.01O₃) by scanning electron microscopy (SEM) in secondary electron emission mode with a small acceleration voltage. Using SEM at an acceleration voltage of 1.0 kV otherwise homogenous surface charging effects are reduced, polarization charges can be observed and polarization directions (±P_z) of the ferroelectric domains in the polycrystalline thin films can be identified. Thin films of different chemical composition have been deposited by pulsed laser deposition on Pt/SiO₂/Si structures under otherwise same growth conditions. Using SEM it has been shown that different charged domain density networks are existing in polycrystalline yttrium manganite thin films.

We present a novel and easy approach using a silicon-based impedance chip to determine the concentration of the given aqueous buffer solution. An accurate determination of the post-dilution concentration of the buffers is necessary for ensuring optimal buffer capacity, pH stability, and to assess solution reproducibility. In this study, we focused on phosphate buffer as the test liquid to achieve precise post-dilution concentration determinations. The impedance chip consisting of a top gold ring electrode, where a test volume of 20 μL to 30 μL of phosphate buffer was introduced for impedance measurements within the frequency range of 40 Hz to 1 MHz. For impedance investigation, we used phosphate buffers with three different pH values, and the impedance was measured after diluting the phosphate buffers to a concentration of 1.00 M, 0.75 M, 0.50 M, 0.25 M, 0.10 M, 0.05 M, and 0.01 M. In order to analyze the distinctive changes in the measured impedance, an equivalent circuit was proposed and modeled. From the impedance modeling, we report that the circuit parameter R_Au/Si showed exponential dependence on the concentration of phosphate buffer and no dependence on the pH values of the phosphate buffer and on the added volume inside the ring electrode. The proposed silicon-based impedance chip is quick and uses reduced liquid volume for post-dilution concentration measurements of buffers and has perspective applications in the pharmaceutical and biological domains for regulating, monitoring, and quality control of the buffers.