ZrO2-based resistive switching memory has attracted much attention according to its possible application in the next-generation nonvolatile memory. The Al/ZrO2/Pt resistive switching memory with bipolar resistive switching behavior is revealed in this work. The thickness of the ZrO2 film is only 20 nm. The device yield improved by the non-lattice oxygen existing in the ZrO2 film deposited at room temperature is firstly proposed. The stable resistive switching behavior and the long retention time with a large current ratio are also observed. Furthermore, it is demonstrated that the resistive switching mechanism agrees with the formation and rupture of a conductive filament in the ZrO2 film. In addition, the Al/ZrO2/Pt resistive switching memory is also possible for application in flexible electronic equipment because it can be fully fabricated at room temperature.

ZrO2-based resistive switching memory has attracted much attention according to its possible application in the next-generation nonvolatile memory. However, the resistive switching mechanism of the ZrO2-based memory device is still controversial. In this study, the mechanism of the ZrO2-based memory device is demonstrated that the resistive switching occurs because of the migration of Ag+ ions. While a positive voltage is applied, Ag+ ions in the ZrO2 film migrate to connect the Pt bottom electrode, causing the formation of Ag conductive bridge. On the other hand, while a negative voltage is applied, Ag+ ions migrate toward the Ag top electrode, leading to the rupture of the Ag conductive bridge. In addition, the resistive switching properties of the ZrO2-based memory device, such as switching voltages and non-destructive readout property, are also demonstrated in this study. Based on the experimental results, the ZrO2-based memory device with clear resistive switching mechanism can be possibly used in the next-generation nonvolatile memory.

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In this work, the effects of crystallization and non-lattice oxygen atoms on the Cu(x)O-based memory device are investigated. The 150 degrees C-deposited Cu(x)O film possesses a larger amount of non-lattice oxygen atoms than those deposited at the higher temperatures, leading to the formation of AIOy interface layer during the sputtering deposition of Al top electrode. Resistive switching occurring within the interface layer is easily controlled, so the set and reset voltages are decreased. In addition, it is demonstrated that the set and reset processes agree with the formation and rupture of a conductive filament in the Cu(x)O film. The 150 degrees C-deposited Cu(x)O-based memory device with good non-volatility is possibly used in the next-generation non-volatile memory.

ZrO 2 -based resistive random access memory possessing stable resistive switching is investigated in this work. The bipolar resistive switching found in Al/ZrO 2 /Pt device shows more promising for application due to its distinguishable switching voltages. Furthermore, good endurance and retention time with a large resistive ratio are also observed in the device. All the fabricating steps of the device were carried out at room temperature, and it is possible for application in flexible electronic equipments.Keywords-non-volatile memory; resistive random access memory; bipolar resistive switching; zirconium oxide; retention time. I. ITRODUCTIONRecently, a novel non-volatile memory, resistive random access memory (RRAM), has been studied extensively due to its great potential of non-volatility, low operation voltage, low power consumption, high operation speed, and simple structure [1]. In particular, ZrO 2 -based RRAM that is compatible with the conventional CMOS process has attracted more and more attention [2]. In the previous studies [3]-[7], Al/ZrO 2 /Pt structure devices showed a unipolar resistive switching behavior that could cause a switching error during performing the resistive switching. In this work, however, the device with bipolar resistive switching behavior is revealed. The device with bipolar resistive switching is more reliable for memory application. In addition, the Al/ZrO 2 /Pt RRAM device reported in this work was fabricated at room temperature (RT), and it is possible for application in flexible electronic equipments. II. EXPERIMENTSA 20-nm-thick Ti adhesion layer and a 60-nm-thick Pt bottom electrode (BE) were successively deposited on a SiO 2 /Si substrate by an electron beam evaporation. After that, an about 20-nm-thick ZrO 2 layer was deposited on the substrate by a radio-frequency magnetron sputtering system. Then, Al top electrodes (TEs) were deposited on the ZrO 2 layer by the sputtering system. The area of the TEs defined by a shadow mask was 4.9×10 -4 cm 2 . All of the fabricating processes were carried out at RT.Electrical properties of the Al/ZrO 2 /Pt device were recorded by Keithley 2400 source meter. During the electrical measurements, a bias voltage was applied on the Al TE, while the Pt BE was grounded, as shown in Fig. 1. (b) show the typical I-V curves of the Al/ZrO 2 /Pt device under unipolar and bipolar resistive switching, respectively. The device can be switched from high resistance state (HRS) to low resistance state (LRS) by applying a positive bias voltage, called SET process. The device can be switched back to the HRS by applying positive or negative bias, called RESET process. The RESET process is voltage polarity independent. During the SET process, a current compliance is set at 10 mA to prevent permanence degradation of the device; however, no current compliance is used at the RESET process. The SET and the RESET processes can be stably reproduced for many times. The resistive ratio between the HRS and the LRS is over 10 4 times. III. RESULTS AND DISCUSSION Fig....