Silicon compatible Sn-based resistive switching memory

Liu

et al. 2019

Adv Elect Materials

computation-in-memory paradigm with new electronic devices when handling data-intensive tasks. [1,2] One important attempt is the recently well explored memristor, [3][4][5] in which the nonlinear dynamics of the device allows on demand modulation of the conductance for direct logic operation while the capability of memorizing the new conductance state enables data storage at exactly the same physical location. [6,7] Eliminating the frequent data fetching and movement between the separated memory and processing units, memristors with the simplicity of a resistor structure can lead to extremely compact crossbar array for highly efficient hardware systems. [8,9] In particular, the elaborate evolution of the conductive filament via local ion motion and electrochemistry including foreign cations (such as Ag + and Cu 2+ injected from electrochemically active metal electrodes) and native oxygen anions or vacancies (O 2− or V O ) are widely used to construct atomic point contacts (APCs) with quantized conductance features. [10][11][12][13][14] The stepwise development of device conductance in the unit of conductance quantum G 0 = 2e 2 /h = 77.5 µS (where e is the elemental charge of electrons and h is the Planck's constant), [10] associated with the continuous yet precise atomic Quantum-level manipulation of atomic configuration offers a excellent platform for the construction of exotic nanostructures that exhibit unusual solid-state physics and electronic properties. One particular example is the memristor, in which the elaborate evolution of atomic point contact via local ionic processes and consequent stepwise device conductance quantization enable bottom-up design of in-memory computing with greatly increased data storage density and more efficient multi-value logic algorithm. In-depth understanding on the physics of atomic reconfiguration is achieved through comprehensive consideration of the thermodynamics and kinetics of nanoionics in memristors, based on which a general protocol of constructing atomic point contact structure with desired quantized conductance is established. Through energy-driven single-atom level oxygen manipulation in the reset process of a Pt/HfO x /ITO structure, up to 32 consecutive quantized conductance states with an interval of half conductance quantum that can be sustained for over 7000 s and tuned 500 times are demonstrated for the first time, not only allowing the physical implementation of ternary logic-inmemory functions, but also providing a universal methodology for building next-generation quantum electronic devices.

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Controllable and Stable Quantized Conductance States in a Pt/HfO_x/ITO Memristor

Liu

et al. 2019

Adv Elect Materials

“…Since oxygen ions often have a higher diffusion barrier than silver and copper ions in oxide films, [45,90] highly stable quantum conductance states are thus more likely to be obtained in memristors with oxygen vacancy filaments. First, a thorough understanding on the physical origin of integer as well as half-integer quantum conductance is urgently required, which may serve as a guide for optimizing the performance of quantum conductance in memristors in future.…”

Section: Challenges and Outlookmentioning

confidence: 99%

Recent Advances of Quantum Conductance in Memristors

Gao

Shang

et al. 2019

Adv Elect Materials

based on a resistive switching Pt/TiO 2−x / TiO 2 /Pt device (Figure 1b), since when the long-standing resistive switching devices over the past half century were all regarded as memristors [3] and aroused ever increasing research interest all over the world for promising nonvolatile memory, logic-in-memory as well as neuromorphic computing applications. [4][5][6][7][8] Memristors usually consist of a simple "metal/insulator/metal" sandwich structure and can be reversibly switched between a high resistance state (HRS, or off state) and a low resistance state (LRS, or on state) under external electrical stimuli. [6] Despite various switching mechanisms have been proposed and solidly confirmed, [7,8] of particular interest and importance is the ion migration-based filamentary mechanism that can ensure an enhanced performance as the device scaling down (Figure 1c). Excellent device miniaturization of <10 nm, [9,10] ultrafast operation speed of <1 ns, [11,12] and extreme switching endurance of >10 12 cycles [13] have been demonstrated in memristors with filamentary mechanism, in addition to their abundant storage media including oxides, nitrides, chalcogenides, polymers, and etc. [7,8] Room-temperature quantum conductance has also been found in these memristors when the size of conducting filaments is reduced down to atomic scale, [14][15][16] as schematically shown by the panels (ii) and (iii) in Figure 1c. In this scenario, the device conductance G is able to be expressed as

“…This can be ascribed to the polarizability increasing in the series Ag→Ni→Pt, as well as higher charge numbers and sizes of Ni and Pt ions [78], which leads to their diffusion being difficult in switching layers. As such, Ag − /Cu − species can transport more easily in dielectrics [38] (especially Si [79]), which introduces defect centers into the integrated silicon circuitry [80]. Guha et al [79] employed first principles calculations for estimating diffusion barriers of active ions in HfO x .…”

Section: Electrode Engineeringmentioning

confidence: 99%

“…As such, Ag − /Cu − species can transport more easily in dielectrics [38] (especially Si [79]), which introduces defect centers into the integrated silicon circuitry [80]. Guha et al [79] employed first principles calculations for estimating diffusion barriers of active ions in HfO x . It is identified that Sn possesses a slower diffusion barrier without creating active defects, which reduces contamination risk than Cu and Ag.…”

Section: Electrode Engineeringmentioning

confidence: 99%

Solid-State Electrochemical Process and Performance Optimization of Memristive Materials and Devices

Liu

2019

Chemistry

As an emerging technology, memristors are nanoionic-based electrochemical systems that retains their resistance state based on the history of the applied voltage/current. They can be used for on-chip memory and storage, biologically inspired computing, and in-memory computing. However, the underlying physicochemical processes of memristors still need deeper understanding for the optimization of the device properties to meet the practical application requirements. Herein, we review recent progress in understanding the memristive mechanisms and influential factors for the optimization of memristive switching performances. We first describe the working mechanisms of memristors, including the dynamic processes of active metal ions, native oxygen ions and other active ions in ECM cells, VCM devices and ion gel-based devices, and the switching mechanisms in organic devices, along with discussions on the influential factors of the device performances. The optimization of device properties by electrode/interface engineering, types/configurations of dielectric materials and bias scheme is then illustrated. Finally, we discuss the current challenges and the future development of the memristor.