Atomic Switch Research Articles

Avalanche atomic switching in strain engineered Sb2Te3–GeTe interfacial phase-change memory cells

By confining phase transitions to the nanoscale interface between two different crystals, interfacial phase change memory heterostructures represent the state of the art for energy efficient data storage. We present the effect of strain engineering on the electrical switching performance of the –GeTe superlattice van der Waals devices. Multiple Ge atoms switching through a two-dimensional Te layer reduces the activation barrier for further atoms to switch; an effect that can be enhanced by biaxial strain. The out-of-plane phonon mode of the GeTe crystal remains active in the superlattice heterostructures. The large in-plane biaxial strain imposed by the layers on the GeTe layers substantially improves the switching speed, reset energy, and cyclability of the superlattice memory devices. Moreover, carefully controlling residual stress in the layers of –GeTe interfacial phase change memories provides a new degree of freedom to design the properties of functional superlattice structures for memory and photonics applications.

(Invited) Challenges to Implement Resistive Memory Cells in the CMOS BEOL

Building nonvolatile memory directly into a CMOS back end of line (BEOL) would reduce latency in connectivity constrained computational devices and reduce chip’s footprint by stacking non-volatile memory on top of the logic circuits. The interconnect delay time is, presently, the most severe bottleneck in microprocessor performance, especially when it comes to the long communication lines between logic and memory. A resistive switching memory cell, in general, consists of a capacitor-like metal-insulator-metal (MIM) structure, often with Cu as one of the two electrodes, called, the active electrode, and an insulating dielectric between the two electrodes, and thus closely prefigures the basic metallization structure of CMOS back end of line (BEOL). Nonvolatile Cu atom switch having structural simplicity and a high on/off current ratio is a strong candidate to realize a highly scalable nonvolatile programmable logic, achieving small energy consumption and high functional flexibility without CMOS scaling. Organic as well inorganic materials have been employed to fabricate resistive switches for memory applications. In this context, the MIM memory cells can either represent a random access memory (RAM) cell or a reconfigurable via realized as a programmable read-only memory (PROM). The latter PROM cell can be used to define a hierarchy of reconfigurable interconnects that allow transistors to be wired together and thus realize a field programmable gate array (FPGA) functionality. Thus a resistive switching cell can play an important dual role if successfully implemented into the CMOS BEOL. The paper discusses the challenges of integration of such a RRAM and FPGA capability into CMOS BEOL. The challenges include: 1) material compatibility, 2) process compatibility (especially, the thermal budget), 3) the integrity of the embedment of the resistive switching cell proper into the back end module, and 4) the choice of the conductive filament (CF), i.e. Cu vs defect, such as oxygen vacancies, CF. The exploration begins with a reliable and well-characterized Cu/TaOx/Pt device, as a benchmark cell, and investigates whether the TaOx dielectric can be replaced by a low-k dielectric of the a-SiOC:H-type, or by porous dielectrics with porosities up to 25%, or by polyimide layers appropriately doped with metallic nanoparticles or graphene nano-platelets, and, finally, whether the rather expensive Pt inert electrode can be replaced by a more economic choice of the inert metal electrode choices such as Ta, Ru, Ir, Co, W, TaN, or Rh, some of which have already been considered as Cu diffusion barriers or liners in CMOS BEOL. It will be shown that depending on the material choices such resistive switching devices can be operated in narrow ranges of parameters such as compliance current, Icc, and voltage or current ramp rate which need to be translated into appropriately tailored programming and erase pulses. One particular circumstance that comes here to the fore are the mechanisms responsible for the programming and erase operations. During the erase and programing transient operations, local temperatures at the conductive filament may exceed 650 oC, even if for a very short time, and, hence, may trigger unintended anneals and even chemical reactions. This has bearing on how the device is being integrated into a given technology module. It can be shown that nominally the same device with excellent resistive switching characteristics in a specific ‘experimental’ environment, may show vastly degraded characteristics when embedded into a module such as the CMOS metallization backend. Such embedment/integration issues have been largely disregarded in the past, so far. The exploration of RRAM/PROM devices compatible with CMOS backend has lead to the discovery of interesting new mechanisms shedding light on the nature of the filament, its formation and its rupture. For example, in the case of polymers doped with graphene nano-platelets with Cu and Au electrodes, resistive switching has been observed to be accompanied by integer and partial quantized conductance at zero magnetic field and room temperature. The quantized conductance is likely the result of the formation of a 1-D wave guide with a voltage-tunable transmission coefficient. It has been shown that the same polymers when highly doped with graphene nano-platelets could act as highly conductive and transparent electrodes. In case of porous dielectrics, the Cu diffusion integrity and Cu filament formation requires an atomistic understanding of Cu drift and diffusion in porous media. In general, we have observed on porous dielectrics with porosity between 0% to 46% porosity, that while the Cu ion diffusion is not much impacted by the porosity level, the Cu drift is highly dependent on the porosity level as evidenced by the increasing programming voltages with increasing porosities.

DFT Study on C-F Bond Activation by Group 14 Dialkylamino Metalylenes: A Competition between Oxidative Additions versus Substitution Reactions.

The C-F bond activation of pentafluoropyridine (PFP) by group 14 dialkylamino metalylenes has been studied employing DFT calculations. Emphasis is placed on the group 14 central atom (M = SiII, GeII, and SnII) and substituents (-NMe2, -NiPr2, -Cl, -NH2, and -PH2) dependent switching of oxidative addition to the metathesis/substitution reaction route, using state-of-the-art theoretical methods (M062X/def2-QZVP(SMD)//M062X/def2-TZVP) to provide a systematic classification of the individual mode of reactions. Moreover, an energy decomposition analysis (EDA) is implemented to get a brief insight into the physical factors that control the activation barriers originating via the different mode of reactions, viz., oxidative addition and metathesis routes. The key finding is that the distortion of PFP is the principal guiding factor in the oxidative addition reaction, while distortions imposed on both the PFP and metalylenes are inevitable toward the origin of the metathesis reaction barrier. The preferable oxidative addition reaction over metathesis of substituted silylenes can be explained on the basis of electron concentration and the HOMO-LUMO gap between the reacting substrates. However, the dramatic switch between oxidative addition and metathesis reaction in substituted germylenes depends on both the electronic and steric nature of the substituents. Similar observations are also noted for the reactivity of substituted stannylenes.

Poly-4-vinylphenol (PVP) and Poly(melamine-co-formaldehyde) (PMF)-Based Atomic Switching Device and Its Application to Logic Gate Circuits with Low Operating Voltage.

In this study, we demonstrate a high-performance solid polymer electrolyte (SPE) atomic switching device with low SET/RESET voltages (0.25 and -0.5 V, respectively), high on/off-current ratio (105), excellent cyclic endurance (>103), and long retention time (>104 s), where poly-4-vinylphenol (PVP)/poly(melamine-co-formaldehyde) (PMF) is used as an SPE layer. To accomplish these excellent device performance parameters, we reduce the off-current level of the PVP/PMF atomic switching device by improving the electrical insulating property of the PVP/PMF electrolyte through adjustment of the number of cross-linked chains. We then apply a titanium buffer layer to the PVP/PMF switching device for further improvement of bipolar switching behavior and device stability. In addition, we first implement SPE atomic switch-based logic AND and OR circuits with low operating voltages below 2 V by integrating 5 × 5 arrays of PVP/PMF switching devices on the flexible substrate. In particular, this low operating voltage of our logic circuits was much lower than that (>5 V) of the circuits configured by polymer resistive random access memory. This research successfully presents the feasibility of PVP/PMF atomic switches for flexible integrated circuits for next-generation electronic applications.

Hydrogen-Induced Oxygen Vacancy Bistability and Its Impact on RRAM Device Operation

Hydrogen-induced bistability of an oxygen vacancy defect was investigated in hafnium oxide using density functional theory calculations. With the injection of an excess electron, a bistability is induced by hydrogen site preference change due to excess electron charge redistribution near the hydrogen and oxygen vacancy. The spatial charge delocalization of electrons is altered in this transition, and this process can have a strong effect on the charge transport probability near conductive filaments of resistive random access memories. If the thickness of HfO2 scales down below 1 nm, the bistability can also be used to realize an atomic resistive switch controlled by a single hydrogen atom.

Quantized conductance operation near a single-atom point contact in a polymer-based atomic switch

Highly-controlled conductance quantization is achieved near a single-atom point contact in a redox-based atomic switch device, in which a poly(ethylene oxide) (PEO) film is sandwiched between Ag and Pt electrodes. Current–voltage measurements revealed reproducible quantized conductance of ∼1G0 for more than 102 continuous voltage sweep cycles under a specific condition, indicating the formation of a well-defined single-atom point contact of Ag in the PEO matrix. The device exhibited a conductance state distribution centered at 1G0, with distinct half-integer multiples of G0 and small fractional variations. First-principles density functional theory simulations showed that the experimental observations could be explained by the existence of a tunneling gap and the structural rearrangement of an atomic point contact.

P-type polymer-based Ag2S atomic switch for “tug of war” operation

The Ag2S gap-type atomic switch based “tug of war” device is a promising element for building a new type of CMOS free neuromorphic computer-hardware. Since Ag+ cations are reduced during operation of the device, it was thought that the gap-material should be a n-type polymer. In this study, we revealed that the polymer bithiophene–oligoethyleneoxide (BTOE) doped poly(ethylene oxide) (PEO), which was used as gap-material in the first demonstration of the “tug of war”, is a p-type polymer. For this we used impedance spectroscopy and transistor measurements. We elaborate on how the electrochemical processes in the “tug of war” devices could be explained in the case of p-type conductive gap-materials.

Set/Reset Switching Model of Cu Atom Switch Based on Electrolysis

A set/reset switching model of Cu atom switch based on electrolysis is newly proposed. A nanometer-thick solid electrolyte gives a high electric field of ~3.3 MV/cm in the solid electrolyte at 2 V, enabling an ionization of Cu and a formation of Cu bridge. It is revealed that the switching voltage depends on the resistance of electrolyte, where the modified Faraday’s law of electrolysis with exponential factors on current and time well falls on the experimental on-resistance. The proposed simple compact model is useful for estimating the resistance of the Cu atom switch programmed by any conditions.

Stochastic resonance in bistable atomic switches

We have investigated the conductance of bistable gold atomic switches as a function of periodic input voltages mixed with a random noise. With increasing noise amplitude, the atomic switches biased below the threshold voltage for conductance switching start exhibiting switching in conductance between two stable states. Clear synchronization between the input and output signals is observed when an optimized noise amplitude is mixed with the periodic input voltage, even when the atomic switches are driven by an input voltage as low as approximately 10% of the threshold voltage. The observed behavior can be explained in terms of the stochastic resonance. The results presented here indicate that utilization of noise can dramatically reduce the operation voltage of metal atomic switches.

Highly Reproducible and Regulated Conductance Quantization in a Polymer‐Based Atomic Switch

A detailed understanding of the conductance quantization and resistive switching phenomena in redox‐based memories is crucial for realizing atomic‐scale memory devices and for finding the adequate design principles on which they can be based. Here, the emergence of quantized conductance states and their correlation with resistive switching characteristics in polymer‐based atomic switches are investigated using combinations of current–voltage measurements and first‐principles density functional theory (DFT) simulations. Various conductance states, including integer and half‐integer multiples of a single atomic point contact and fractional conductance variations, are observed in an Ag/polyethylene oxide/Pt device under sweeping of bias voltage. Moreover, highly controllable and reproducible quantized conductance behaviors by tuning the voltage sweep rate and the sweep voltage range, suggesting well‐controlled formation of the atomic point contact, are demonstrated. The device also exhibits longer retention times for higher conductance states. The DFT simulations reveal the transmission eigenstate of geometrically optimized atomic point contact structures and the impact of the atomic configurations and structural stability on the conductance state, which also explains their resistive switching behaviors. The well‐defined, multiple quantized conductance states observed in these polymer‐based atomic switches show promise for the development of new multilevel memory devices.

Operating mechanism and resistive switching characteristics of two- and three-terminal atomic switches using a thin metal oxide layer

Atomic switches are nanoionic devices that are operated by controlling redox reactions and the local migration of metal ions in solids. The essential mechanism is the growth and shrinkage of a metal filament formed between two electrodes, resulting in repeatable resistive switching between high-resistance and low-resistance states, which can be used for next-generation nonvolatile memories. This review focuses on the operating mechanism and resistive switching characteristics of two- and three-terminal atomic switches using a thin metal oxide layer as an ion-conducting matrix. First, we describe the operating mechanism of a two-terminal atomic switch based on nucleation theory and present the results of temperature dependence and switching speeds to determine the validity of our switching model. Then, we discuss the effects that moisture absorption in the oxide matrix has on the fundamental processes and switching behavior in order to elucidate the importance of the porosity of the oxide matrix. Finally, we demonstrate a three-terminal atomic switch and describe the impact of the anode material or metal-ion species. These findings will contribute to the development of next-generation logic circuits with low-voltage operation and low-power consumption.

Chemical and structural arrangement of the trigonal phase in GeSbTe thin films

The thermal and electrical properties of phase change materials, mainly GeSbTe alloys, in the crystalline state strongly depend on their phase and on the associated degree of order. The switching of Ge atoms in superlattice structures with trigonal phase has been recently proposed to develop memories with reduced switching energy, in which two differently ordered crystalline phases are the logic states. A detailed knowledge of the stacking plane sequence, of the local composition and of the vacancy distribution is therefore crucial in order to understand the underlying mechanism of phase transformations in the crystalline state and to evaluate the retention properties. This information is provided, as reported in this paper, by scanning transmission electron microscopy analysis of polycrystalline and epitaxial Ge2Sb2Te5 thin samples, using the Z-contrast high-angle annular dark field method. Electron diffraction clearly confirms the presence of compositional mixing with stacking blocks of 11, 9 or 7 planes corresponding to Ge3Sb2Te6, Ge2Sb2Te5, and GeSb2Te4, alloys respectively in the same trigonal phase. By increasing the degree of order (according to the annealing temperature, the growth condition, etc) the spread in the statistical distribution of the blocks reduces and the distribution of the atoms in the cation planes also changes from a homogenous Ge/Sb mixing towards a Sb-enrichment in the planes closest to the van der Waals gaps. Therefore we show that the trigonal phase of Ge2Sb2Te5, the most studied chalcogenide for phase-change memories, is actually obtained in different configurations depending on the distribution of the stacking blocks (7–9–11 planes) and on the atomic occupation (Ge/Sb) at the cation planes. These results give an insight in the factors determining the stability of the trigonal phase and suggest a dynamic path evolution that could have a key role in the switching mechanism of interfacial phase change memories and in their data retention.

High performance bi-layer atomic switching devices.

Atomic switches, also known as conductive bridging random access memory devices, are resistive-switching devices that utilize the electrochemical reactions within a solid electrolyte between metal electrodes, and are considered essential components of future information storage and logic building blocks. In spite of their advantages as next generation switching components such as high density, large scalability, and low power consumption, the large deviations in their electrical properties and the instability of their switching behaviors hinder their application in information processing systems. Here, we report the fabrication of a uniform, low-power atomic switch with a bi-layer structure consisting of Ta2O5-x as the main switching layer (SL) and a relatively oxygen-deficient TaOx as an oxygen vacancy control layer (VCL). The depth profiles of the filaments in the bi-layer device were obtained by performing conductive atomic force microscopy to assess the improvements in uniformity, reliability, and electrical performance that result from the insertion of the VCL. The coefficient of variation of the high resistance state of the bi-layer device was found to be drastically reduced from 60.92% to 2.77% in the cycle-to-cycle measurements and from 82.73% to 4.85% in the device-to-device measurements when compared with the values obtained for a single-layer device. The bi-layer device also exhibits a forming-free low operation voltage of ∼0.4 V, a high on/off ratio of ∼106, and high reliability with 10 years data retention at 85 °C.

Corn starch solid electrolyte gated proton/electron hybrid synaptic transistor

A human brain is a high-density neural network, which has~1011 neurons and~1015 synapses. Neuron as a basic information processing unit builds the biological neural network, and the realization of information transmission and integration depends on the synaptic connection between neurons. This information transfer and integration work is difficult to realize by relying on von Neumann computer, due to the computer only works according to the well-defined programs. To further simulate the imagery thinking of human brain neural network, the researchers begin with the information memory and processing mechanism of human brain neural network. A large number of microelectronic devices with human thinking characteristics are designed, such as memristor, atomic switch, phase change memory, and transistors. The oxide-based thin film transistor under the new material system is one of these devices, and has attracted the attention of researchers. The transistors working as the biological synapses, the gate electrode is regard as presynaptic input terminal, and the channel current is measured as postsynaptic output. Utilizing the proton gating behaviors, a series of synaptic behaviors, such as short-term and long-term memory, paired-pulse facilitation, and spike timing-dependent plasticity is mimicked successfully in these synaptic transistors.#br#With the progressing of science and technology, and the increasing of requirements for environmental protection, researchers pay more attention to the environmentally friendly solid electrolyte materials to fabricate oxide-based thin film synaptic transistor. Researchers have a major interest in starch, due to the low price, rich source, and excellent mechanical properties. Starch can be extracted from corn, potato, sweet potato and other starch-containing substances, and is generally insoluble in cold water, and gelatinized in boiling water. In this study, corn starch solid electrolyte is prepared on ITO glass by spin coating progress, and dried at a constant temperature at 30℃. The electrical performances of protonic/electronic hybrid IZO synaptic transistor gated by corn starch solid electrolyte are excellent, operation voltage, Ion/off ratio, field-effect mobility and subthreshold swing are 1.5 V, 1×107, 18.7 cm2·V-1·s-1 and 156.8 mV/dec., respectively. Due to the mobile proton migrating in corn starch solid electrolyte, the paired-pulse facilitation, learning and memory behaviors and high-pass filter of biological neural synaptic plasticity are realized successfully. The synaptic transistors have potential applications in the field of environment-friendly microelectronic devices to reduce the production costs. Therefore, the corn starch solid electrolyte gated proton/electron hybrid synaptic transistor as an artificial synapse can offer a suitable option to building the neural network.

Communication—Excellent Threshold Selector Characteristics of Cu2S-Based Atomic Switch Device

Bipolar-threshold switching was demonstrated using volatile-atomic switches (VAS) for cross-point selector applications. The VAS (Cu/Cu2S/W) exhibits asymmetric current–voltage (I–V) characteristics. An abrupt conductance change occurs by the formation of a Cu filament when a positive voltage is applied to the Cu electrode. Meanwhile, nonlinear I–V characteristics are observed because of the high concentration of vacancy of Cu under a negative voltage. We thus introduce the complementary-VAS configuration for the self-compliance characteristics at both polarities. Furthermore, the increased the switching voltage at a fast sweeping rate allows the VAS to show a strong immunity to electrical disturbance.

Atomic Layering, Intermixing and Switching Mechanism in Ge-Sb-Te based Chalcogenide Superlattices.

GeSbTe-based chalcogenide superlattice (CSLs) phase-change memories consist of GeSbTe layer blocks separated by van der Waals bonding gaps. Recent high resolution electron microscopy found two types of disorder in CSLs, a chemical disorder within individual layers, and SbTe bilayer stacking faults connecting one block to an adjacent block which allows individual block heights to vary. The disorder requires a generalization of the previous switching models developed for CSL systems. Density functional calculations are used to describe the stability of various types of intra-layer disorder, how the block heights can vary by means of SbTe-based stacking faults and using a vacancy-mediated kink motion, and also to understand the nature of the switching process in more chemically disordered CSLs.

Single-Atom Switches and Single-Atom Gaps Using Stretched Metal Nanowires.

Utilizing individual atoms or molecules as functional units in electronic circuits meets the increasing technical demands for the miniaturization of traditional semiconductor devices. To be of technological interest, these functional devices should be high-yield, consume low amounts of energy, and operate at room temperature. In this study, we developed nanodevices called quantized conductance atomic switches (QCAS) that satisfy these requirements. The QCAS operates by applying a feedback-controlled voltage to a nanoconstriction within a stretched nanowire. We demonstrated that individual metal atoms could be removed from the nanoconstriction and that the removed metal atoms could be refilled into the nanoconstriction, thus yielding a reversible quantized conductance switch. We determined the key parameters for the QCAS between the "on" and "off" states at room temperature under a small operating voltage. By controlling the applied bias voltage, the atoms can be further completely removed from the constriction to break the nanowire, generating single-atom nanogaps. These atomic nanogaps are quite stable under a sweeping voltage and can be readjusted with subangstrom accuracy, thus fulfilling the requirement of both reliability and flexibility for the high-yield fabrication of molecular devices.

Nanoarchitectonic atomic switch networks for unconventional computing

Developments in computing hardware are constrained by the operating principles of complementary metal oxide semiconductor (CMOS) technology, fabrication limits of nanometer scaled features, and difficulties in effective utilization of high density interconnects. This set of obstacles has promulgated a search for alternative, energy efficient approaches to computing inspired by natural systems including the mammalian brain. Atomic switch network (ASN) devices are a unique platform specifically developed to overcome these current barriers to realize adaptive neuromorphic technology. ASNs are composed of a massively interconnected network of atomic switches with a density of ∼109 units/cm2 and are structurally reminiscent of the neocortex of the brain. ASNs possess both the intrinsic capabilities of individual memristive switches, such as memory capacity and multi-state switching, and the characteristics of large-scale complex systems, such as power-law dynamics and non-linear transformations of input signals. Here we describe the successful nanoarchitectonic fabrication of next-generation ASN devices using combined top-down and bottom-up processing and experimentally demonstrate their utility as reservoir computing hardware. Leveraging their intrinsic dynamics and transformative input/output (I/O) behavior enabled waveform regression of periodic signals in the absence of embedded algorithms, further supporting the potential utility of ASN technology as a platform for unconventional approaches to computing.

Joule Heating Effect in the Electroforming Process of Pt/WO 3-X /Pt Nanoionics-Based Memristive Devices

In recent years, nanoionics-based memristive devices with resistive switching behaviors have garnered significant attention as promising candidates for next-generation nonvolatile memory known as resistance random access memory (RRAM) due to their potential high scalability and low-power consumption. In addition, memristive devices are also promising for logic and neuromorphic computations. The memristive devices typically have a simple stacked structure of metal-insulator-metal (MIM), where the resistance can be reversed changed through local ion migration and electrochemical reaction after an initial electroforming process. Nanoionics–based memristive devices can be classified as cation migration cells and anion migration cells. When an electrochemically active electrode such as one made of Ag or Cu is used in a MIM device, resistive switching occurs through formation and annihilation of a metallic atom bridge resulting from the migration of highly mobile cations such as Ag+ and Cu+ ions. This type of nanoionics-based device is referred to as an atomic switch or electrochemical metallization systems.[1] Resistive switching behavior can also be observed for a MIM device without an electrochemically active electrode. In this case, the migration of anions, usually oxygen ions plays a crucial role. Local oxygen ion migration, which is better described as the migration of oxygen vacancy (V O ‥) and a resultant change in the electronic barrier at the metal electrode/TMO interface, is associated with the resistive switching behavior. In general, the cation migration cell and anion migration cell both need electroforming process to obtain resistive switching behaviors. For the cation migration cells, the formation of Ag or Cu bridges in the forming process has been directly observed by TEM or in-situ TEM.[2]In contrast, the mechanism of the electroforming process in the anion migration cell is still uncertain due to the lack of direct characterization. In this study, the electroforming process and resistive switching behaviors of the anion migration cell of Pt/WO3-x/Pt have been investigated as a function of temperature. As shown in Figure 1a, electroforming process with soft-breakdown was triggered as the sweep voltage was raised to about 6.0 V at 296 K and 396 K. But, at 110 K, no soft-breakdown was observed even by increasing the sweep voltage to 20 V, which indicates that the devices cannot be electroformed at ultralow temperature. In contrast, the device shows resistive switching behaviors at ultralow temperature after being electroformed at room temperature, see Figure 1b. In order to real-time observe the structure changes during electroforming process, we prepared a Pt/WO3-x/Pt devices that operated inside a TEM, see the inset of Figure 1g. As reported in Figure 1c to 1f, the initial amorphous WO3-x layer gradually crystallized by applying voltage weeping. And, crystallized nanoparticles of Magnéli phase were observed, as shown in Figure 1g. Actually, the current level of in situ measurements is much smaller than that in the conventional electroforming processes. This may be the reason why no conductive filament composed of the Magnéli phases was observed. The crystallization and formation of the conductive filament in WO3-x layer have been observed by cutting the electroformed device in our previous work.[3] Based on above results, it is proposed that the Joule heating effect plays a key role in the electroforming process. Under ultralow temperature, the current level of the device is too low to generate enough heating effect to introduce the filament formation. Moreover, the heat dissipates much quickly at ultralow temperature. Therefore electroforming process could not be triggered at ultralow temperature. In contrast, the resistive switching behavior obtained after electroforming process mainly occurs in the nanogap region between the electrode and the conductive filaments, where the V O ‥ migration under external electric field determines the resistive switching process. So, the resistive switching behavior can be observed at low temperature. Based on these results and discussions, it is reasonable to conclude that Joule heating effect domains the electroforming process, instead of the resistive switching processes. Terabe, K.; Hasegawa, T.; Nakayama, T.; Aono, M., Nature 2005, 433, 47-50. Yang, Y.; Gao, P.; Gaba, S.; Chang, T.; Pan, X.; Lu, W., Nat.Commun. 2012, 3, 732. Tan, Z. H.; Yang, R.; Terabe, K.; Yin, X. B.; Zhang, X. D.; Guo, X., Adv. Mater. 2016, 28, 377-384. Figure 1

An atomic symmetry-controlled thermal switch.

We propose a simple diatomic system trapped inside an optical cavity to control the energy flow between two thermal baths. Through the action of the baths the system is driven to a non-equilibrium steady state. Using the Large Deviation theory we show that the number of photons flowing between the two baths is dramatically different depending on the symmetry of the atomic states. Here we present a deterministic scheme to prepare symmetric and antisymmetric atomic states with the use of external driving fields, thus implementing an atomic control switch for the energy flow.