On the stochastic nature of resistive switching in Cu doped Ge0.3Se0.7 based memory devices

Soni, Rohit; Meuffels, P.; Staikov, G.; Weng, R.; Kügeler, C.; Petraru, A.; Hambe, M.; Waser, Rainer; Kohlstedt, H.

doi:10.1063/1.3631013

Cited by 60 publications

(41 citation statements)

References 41 publications

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“…The stepwise variations in Figure 5 c on top of the overall current decay could be explained by the stochastic change in the conduction path due to persistent trapping and detrapping of electrons leading to the rearrangement of the network composed of occupied traps. [ 47,48 ] Such behaviors have been successfully modeled for percolation networks with competing defect generation and defect recovery mechanisms, [ 48,49 ] again supporting electron trapping as the mechanism of the observed switching effect in oxidized graphene electrodes. The difference in retention time between the functionalized graphene electrodes in the MLG/Ta 2 O 5-x /TaO y /MLG devices and the annealed graphene samples may be explained by the different interfaces in the two types of devices, as the TaO y layer passivating the graphene fi lm could change the energy profi le of the electron traps and make it easier for the trapped electrons to escape in the MLG/Ta 2 O 5-x /TaO y /MLG devices.…”

Section: Communicationmentioning

confidence: 89%

Oxide Resistive Memory with Functionalized Graphene as Built‐in Selector Element

Yang

Lee

et al. 2014

Advanced Materials

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transfer was repeated several times (typically ∼3) in order to further improve the conductance of the electrodes, therefore forming a multilayer graphene (MLG) stack. An optical graph of the glass substrate with the MLG fi lm on top is displayed in Figure 1 b, showing high transparency. Subsequently, the MLG fi lm was patterned into bottom electrodes (BEs) with widths of 1-5 µm by photolithography and O 2 plasma etching (Figure 1 a2). Au/Ti metal contacts (B1 and B2) were then deposited onto the two ends of the MLG BE afterwards to minimize the contact resistance to the external probes in electrical measurements (Figure 1 a3). Following BE defi nition, a bilayer oxide structure consisting of an oxygen rich Ta 2 O 5-x layer (∼5 nm) and an oxygen defi cient TaO y layer (∼40 nm) serving as the switching medium of the RRAM devices was successively deposited by radio-frequency (RF) sputtering and reactive sputtering (400 °C, O 2 /Ar = 3%), respectively, without breaking the vacuum (Figure 1 a4). Similar to steps 1-3 in Figure 1 a, multiple monolayer graphene transfer, O 2 plasma etching and Au/Ti metal contacts deposition were conducted again to fabricate the top electrodes (TEs) that complete the crossbar memory structure ( Figure 1 a5-7). Finally, a pad opening step was performed through a timed reactive ion etching (RIE) process to remove the Ta 2 O 5-x /TaO y bilayer on top of the bottom contact Au/Ti pads (Figure 1 a8). The sizes of the RRAM devices in this work range from 1-5 µm × 1-5 µm, and during measurements the voltage was applied on the TE with the BE grounded. Since resistive switching in Ta 2 O 5-x /TaO y bilayer devices is driven by internal oxygen vacancy redistribution, the change in deposition sequence should in principle only lead to a reversal of the switching polarity, as has been verifi ed by studies on devices with inert metal electrodes. [ 25 ] However, in the case of devices with MLG electrodes, the stacking sequence of the bilayer was found to be critical in determining the device behavior, as shown in Figure 1 d,e. When the Ta 2 O 5-x layer was deposited fi rst on the graphene BE followed by TaO y deposition, the MLG/TaO y /Ta 2 O 5-x /MLG (top to bottom) devices exhibited conventional bipolar resistive switching characteristics similar to the results obtained with metal electrodes, [ 25,26 ] as shown in Figure 1 d. Such switching behavior can be well understood in the picture of V O exchange between the Ta 2 O 5-x and the V O -rich TaO y layers, [ 8,26,27 ] and the switching polarity with positive SET and negative RESET voltages is a natural result of the device confi guration since the V O reservoir (the oxygen defi cient TaO y layer) sits on top in this case. The linear on-state behavior is also consistent with Ohmic conduction for the V O -based conducting fi laments in Ta 2 O 5-x /TaO y RRAMs. [ 8,26,27 ] Driven by the continuing demand for improved computing capability, the semiconductor industry has been constantly looking for a fast, reliable, scalable yet nonvolatile memory technolo...

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Section: Communicationmentioning

confidence: 89%

Oxide Resistive Memory with Functionalized Graphene as Built‐in Selector Element

Yang

Lee

et al. 2014

Advanced Materials

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“…It is thus difficult to formulate an expression for the switching time for a voltage sweep. Therefore, we restrict our study to voltage pulses and the nucleation time t nuc is then given by 26,49 …”

Section: Theory and A Simulation Modelmentioning

confidence: 99%

Switching kinetics of electrochemical metallization memory cells

Menzel

Tappertzhofen

Waser

et al. 2013

Phys. Chem. Chem. Phys.

173

161

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The strongly nonlinear switching kinetics of electrochemical metallization memory (ECM) cells are investigated using an advanced 1D simulation model. It is based on the electrochemical growth and dissolution of a Ag or Cu filament within a solid thin film and accounts for nucleation effects, charge transfer, and cation drift. The model predictions are consistent with experimental switching results of a time range of 12 orders of magnitude obtained from silver iodide (AgI) based ECM cells. By analyzing the simulation results the electrochemical processes limiting the switching kinetics are revealed. This study provides new insights into the understanding of the limiting electrochemical processes determining the switching kinetics of ECM cells.

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“…However, as pointed out earlier, this necessary condition is not sufficient to distinguish the ferroelectric-driven TER (FE-TER) from resistance-switching phenomena resulting from-so to speak-'redox' reactions 35 . Indeed, given that the very high coercive fields of ultrathin ferroelectric films fall into the electric-field range where the occurrence of a soft breakdown of the film cannot be excluded, there remain concerns that stochastic redox-based resistance switching might be misinterpreted as the FE-TER [36][37][38][39][40][41] . Therefore, it is of crucial importance to investigate both the TER effect and the redox-based resistive switching in a single FTJ to undoubtedly distinguish between the two different phenomena.…”

mentioning

confidence: 99%

Giant electrode effect on tunnelling electroresistance in ferroelectric tunnel junctions

et al. 2014

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Among recently discovered ferroelectricity-related phenomena, the tunnelling electroresistance (TER) effect in ferroelectric tunnel junctions (FTJs) has been attracting rapidly increasing attention owing to the emerging possibilities of non-volatile memory, logic and neuromorphic computing applications of these quantum nanostructures. Despite recent advances in experimental and theoretical studies of FTJs, many questions concerning their electrical behaviour still remain open. In particular, the role of ferroelectric/electrode interfaces and the separation of the ferroelectric-driven TER effect from electrochemical ('redox'-based) resistance-switching effects have to be clarified. Here we report the results of a comprehensive study of epitaxial junctions comprising BaTiO 3 barrier, La 0.7 Sr 0.3 MnO 3 bottom electrode and Au or Cu top electrodes. Our results demonstrate a giant electrode effect on the TER of these asymmetric FTJs. The revealed phenomena are attributed to the microscopic interfacial effect of ferroelectric origin, which is supported by the observation of redox-based resistance switching at much higher voltages.

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On the stochastic nature of resistive switching in Cu doped Ge0.3Se0.7 based memory devices

Cited by 60 publications

References 41 publications

Oxide Resistive Memory with Functionalized Graphene as Built‐in Selector Element

Oxide Resistive Memory with Functionalized Graphene as Built‐in Selector Element

Switching kinetics of electrochemical metallization memory cells

Giant electrode effect on tunnelling electroresistance in ferroelectric tunnel junctions

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