To prevent this sneak path current, various selection devices are introduced. Selection

devices have very a high resistance at low voltage levels (VLow) and low resistance at high voltage levels (VHigh). Therefore, the use of a selection device and ReRAM integration can reduce the leakage current in cross-point array operation. However, they are structurally and compositionally complex for one-selector one-ReRAM (1S1R) integration [9, 10]. Therefore, selector-less Selleckchem OSI906 ReRAMs with non-linear ILRS behavior and without complex compositional and structural integration have been investigated [11, 12]. However, the origin of the selector-less ReRAM has not been investigated, and its switching reliability has not been considered for cross-point array operation. Most researches have focused only on the selectivity of the selector-less ReRAM. In this research, the multi-functional role of the TiOx tunnel barrier which can be integrated with ReRAM selleck products was analyzed. We significantly improved the selectivity and switching uniformity by designing the device with a simple triple-layer structure of a tunnel-barrier-layer-inserted ReRAM. The tunnel barrier can act as an internal resistor whose resistance changes with the applied bias. Direct tunneling (DT) of the tunnel

barrier shows high resistance at VLow, whereas Fowler-Nordheim tunneling (FNT) shows low resistance at VHigh. DT of the tunnel barrier reduces the sneak-path current of the Depsipeptide nmr ReRAM and controls the filament formation in the HfO2 switching layer for selectivity and uniformity. Thus, the multi-functional

tunnel barrier plays an important role LY333531 in vitro in the selectivity and switching uniformity of ReRAMs. Experiments We fabricated Ti/HfO2/multi-layer TiOy-TiOx/Pt devices in a 250-nm via-hole structure. For the isolation layer, a 100-nm-thick SiO2 sidewall layer was deposited on a Pt bottom electrode (BE)/Ti/SiO2/Si substrate by plasma-enhanced chemical vapor deposition. Subsequently, a 250-nm via-hole was formed by a KrF lithography process, followed by reactive-ion etching. First, a 6-nm TiOx tunnel barrier was deposited in an Ar-and-O2 mixed plasma (Ar/O2 = 30:1 sccm) by radio frequency (RF) sputtering (working pressure 5 mTorr, RF power 100 W). To form the multi-layer TiOy/TiOx (y > x), a tunnel barrier was annealed in O2 ambient by rapid thermal annealing at 300°C. We varied the thermal oxidation time to evaluate the role of the tunnel barrier in the ReRAM (0 to 10 min). Then, a switching layer of 4-nm-thick HfO2 was deposited using an atomic layer deposition system using TEMAH as a precursor and H2O as an oxidizer at 250°C. The Ti oxygen reservoir and a top electrode (TE) of 50 μm were deposited using direct current (DC) sputtering and a shadow mask. Discussion Figure 1a shows the DC current–voltage (I-V) curve, which shows the highly non-linear I-V characteristics of the TE/Ti/HfO2/multi-layer TiOy-TiOx/BE device.