All size devices have shown self-compliance bipolar switching with small set/rest voltage of -1.0/2.0 V. The switching current of 50 × 50 μm2 7-Cl-O-Nec1 concentration device was >200 μA and for 30 × 30 nm2 device was approximately 40 μA, respectively (Figure 10d). From the I-V switching curves, this is a symmetric current profile when the device is in the LRS, but it is an asymmetric current profile for the HRS. This property was exploited to realize RRAM devices in crossbar architecture without any selection device with anti-serial

connection. They were also able to achieve the highest ever reported endurance value of 1012 for this system at 30 × 30 μm2 cell size for base layer oxidation of 3%. Data retention of >10 years at 85°C was also reported. To eliminate the need for a discrete switch element such as a diode or transistor, they connected two Pt/Ta2O5-x /TaO2-x /Pt cells antiserially by external contacts and this concept was also reported Selleckchem Depsipeptide by Linn et al. [134]. Figure 9 Program/erase endurance. Endurance comparison

of (a) TiO x and (b) TaO x devices [110]. Figure 10 Schematic of switching mechanism Selleckchem Afatinib and I-V characteristics of cross-point memory devices. (a) Schematic representation of the TaO x device consisting of a thin Ta2O5-x insulating layer and a TaO2-x base layer. The movement of internal oxygen ions or vacancies is used to model the switching. (b) SEM image of a 30-nm crossbar array of devices with the inset showing a single device. (c) TEM cross-section of a 30-nm crossbar cell. The total thickness of TaO x layer is 30 nm. (d) I-V hysteresis characteristics [31]. Wei et al. [109] explored first the prospective application of TaO x -based RRAM devices. The memory stack consisted of Pt top and bottom electrodes and a non-stoichiometric switching layer of TaO x . The first layer near the TE is close to

insulating Ta2O5-x phase, while the other layer is close to TaO2-x phase which is conducting. The memory device with a size of 0.5 × 0.5 μm2 in 1T1R configuration showed bipolar switching characteristics under an operation current of approximately 170 μA. The device shows excellent P/E endurance of >109 cycles. The data Oxalosuccinic acid retention property could be improved under low-current operation by controlling the size of the conductive filament as well as percolation paths, while the density of oxygen vacancy is kept high enough. It is true that the conducting filament size can be scaled down by reducing both the forming current and formation. A forming voltage can be decreased with a thinner switching layer. However, the thinnest layer is not required because this will have lower HRS. Figure 11a shows a pulsed R-V curve of the two-step forming to control the formation of conducting filament size in Ir/Ta2O5-δ /TaO x resistive memory stack [120]. At first (or step 1), a positive pulse that has the same polarity for the RESET is applied to generate oxygen vacancies in the Ta2O5-δ layer, as shown in Figure 11b.