| Resistive Random Access Memoristors which is based on Electric-Pulse-Induced Resistance Switching(EPIR) are expected to be the new generation of storge devices due to its fast speed of swiching between high and low resistance(<10ns), revisable, good retention and nonvolatility(1010times), which is on the base of electrical pulse induced resistance switching effect at room temperature. In addition, RRAM becomes a hot topic in the field of condensed mater physics, materials science and semiconductors for its simple architecture, high storage density, low power of comsumption (～1PJ/operation) and consistence with CMOS techenology.The cuprous oxide (Cu2O) films and Cu/Cu2O/Cu/FTO, Ag/Cu2O/Cu/FTO, Ag glue/Cu2O/Cu/FTO, Pt/Cu2O/Cu/FTO, Au/Cu2O/Cu/FTO devices are deposited on the base of FTO substrates with different pH values (5,6,7,8,9,10) by using potentiostatic electrochemical deposition. The method of ion sputtering and plating silver glue on the sample surface of Cu2O films are used to prepare different electrodes, and then the devices are examed using direct current (DC) and alternating current (AC) technology via the4-wire and2-wire measurements, respectively. The physical properties of samples, including crystallographic structure, chemical composition, microstructure as well as the magnetoelectric transport are investigated by powder X-ray diffraction, Scanning electron microscope, Electronic diffraction spectra, Mapping analysis, as well as the variable temperatures measuring system combined with the softwares of Labview and Zview. According to the experimental data, the conclusions are as below:(1) Because of four-wire measurement can ignore the impact of the contact interface, the measurement resistance is the intrinsic resistance of the Cu2O film; and two-wire measurement results mainly reflects the characteristics of the sample, electrode-sample interface transport, But its non-linear transport is mainly caused by the Schottky barrier which is in the electrode and the sample interface, and the electric field can reduce the barrier height. In the present system, we find that the contact resistance is an order of magnitude larger than intrinsic resistance by the comparison of the two-wire and four-wire measurement.(2) The EPIR effect of the sample and the measured sample Ⅳ nonlinear are closely linked, that is, the space-charge layer is necessary to the Ⅰ-Ⅴ nonlinear and EPIR effect. In addition, the treatment of external load "power cycle" can significantly improve the status of the contact interface; reduce interface contact barrier, and thus the sample body transport measurements could be implement. (3) The Stable, uniform, compactness cuprous oxide (Cu2O) films and Cu/Cu2O/Cu/FTO device are deposited on the base of FTO substrates with different pH values (5,6,7,8,9,10) by using potentiostatic electrochemical deposition, and the Electric-Pulse-Induced-Resistance (EPIR) switching effect of Cu/Cu2O/Cu/FTO devices are tested as well. The results show that EPIR effect and resistive memory characteristic exist clearly in Cu/Cu2O/Cu/FTO device at room temperature and relate to the pH values of the solution. In the acidic and neutral condition, for example pH=5、6、7, EPIR effect exists clearly in Cu/Cu20/Cu/FTO devices and tends to decrease as the pH value rises, moreover, the most significant EPIR effect appears as the optimal pulse parameters are6V for the pulse amplitude and0.001s for the pulse width. As the pH value rises further in alkaline condition, for example pH=8、9、10, EPIR effect disappears.(4) We manufacture Cu2O/Cu/Cu/FTO, Ag/Cu2O/Cu/FTO, Pt/Cu2O/Cu/FTO, Au/Cu2O/Cu/FTO four kinds of devices by spraying different electrode, then scaning their the Ⅰ-Ⅴ characteristics curve and testing their Electric-Pulse-Induced Resistance Switching effect (EPIR). Results show that if the electrode is more lively, the Ⅰ-Ⅴ characteristic curve of the samples would show stronger nonlinearity and hysteresis. The EPIR effect of the samples decrease in turn as the electrode active sex is abate. Roff/Ron of Ag glue/Cu2O/Cu/FTO and Cu/Cu2O/Cu/FTO devices are up to several orders of magnitude, which can meet the requirements that the device application can be distinguished by external circuit switch ratio is greater than10. The trigger voltage of resistance changes of Cu/Cu2O/Cu/FTO device is very small, only need±1V, which is able to meet the requirements of the low energy actual device. And Cu/Cu2O/Cu/FTO device is very consistent with CMOS techenology, and the preparation technology is simple and mature. These advantages provide convenience for practical application of the device.(5) The Ag glue/Cu2O/Cu/FTO and Ag/Cu2O/Cu/FTO devices was prepared by the methods of coated silver plastic electrode and sputtered Ag electrode, we investigated the effects on the Cu2O EPIR by the different contact of the Cu2O thin film and electrode. The results show that the Ag glue/Cu2O/Cu/FTO exhibit stronger nonlinear Ⅰ-Ⅴ and hysteresis than Ag/Cu2O/Cu/FTO devices, the Ag glue/Cu2O/Cu/FTO device EPIR effects are also more significant.(6) The EPIR effect of the prepared Cu2O device is also related to the applied pulse parameters. Different devices have different optimum pulse parameters. To this research system, the best amplitude A is3-6V, pulse width is0.0001s-0.001s, and the best bias voltage is0.01-0.1V. Not only the excessive scanning voltage improves the Ⅰ-Ⅴ nonlinearity and hysteresis ratio, but also results in unrecoverable interface barrier destruction. So it is very important to choose an appropriate scan voltage for the stable of resistive transition.(7) After repeated scanning of the Ⅰ-Ⅴ characteristics by so called four-wire method, we found that the bulk Cu2O thin film shows the EPIR effect (Bulk RS), it has a bipolarresistor transformation behavior, it have a lower threshold voltage compared to other transition metal oxides. Three devices are lower than0.1V, and all low-resistance state (LRS) and high resistance state (HRS) showed ohmic behavior. The EPIR test of Cu2O film shows a resistive transition to four orders of magnitude. |
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