Abstract The development of analog memristive devices with symmetric and controllable switching is critical for the implementation of neuromorphic hardware capable of spike-based supervised learning. Here, we report a TiO2/Al2O3 bilayer memristor that exhibits filamentary-driven, gradual dual bipolar resistive switching, enabling both spike-timing-dependent plasticity (STDP) and anti-STDP within a single device. The resistance of the TiO2 layer is modulated by the growth dynamics of oxygen vacancy filaments in the Al2O3 layer, which in turn alters the electric field distribution and enables progressive filament formation and rupture. This mechanism allows for the quasi-symmetric, polarity-reversible switching without external circuitry or explicit mode-switching procedures. The device demonstrates a high functional yield of 95% and a low switching voltage variation (coefficient of variation < 3%). Crossbar array integration confirms reliable bidirectional synaptic updates in response to identical input spikes. Furthermore, a simulation incorporating experimentally extracted switching parameters achieves 84.5% classification accuracy on the MNIST dataset using the remote supervised method. These results establish the TiO2/Al2O3 bilayer memristor as a scalable, CMOS-compatible platform for implementing biologically inspired learning rules in next-generation neuromorphic systems.

Biological mechanoreceptors convert tissue strain into distinct spike trains. In contrast, their soft electronic counterparts still rely on discrete components for sensing, preprocessing, and neuronal firing. Here, we integrate these functional components into a single and scalable device by combining mechano-electric transduction and volatile threshold switching within an Ag/freestanding epitaxial SrTiO3/Pt membrane laminated onto a flexible polyethylene naphthalate substrate. Tensile strain (0–2.6

The commercial adoption of graphene for next-generation electronics requires fabrication techniques that are clean, precise, and scalable. Conventional O2 plasma etching with polymer masks causes severe contamination and damage. We introduce a polymer-free method for the selective etching of single-layer graphene (SLG) using a 172 nm Xe2 excimer UV lamp under ambient conditions. This process utilizes high-energy 172 nm photons to directly dissociate atmospheric oxygen and water, enabling rapid, atomic-layer selective etching without vacuum or controlled gas. Raman analysis confirms a clean three-stage chemical transformation (cleaning, oxidation, etching) and shows minimal edge damage compared to plasma methods. The versatility of this technique is demonstrated through the preservation of intrinsic Graphene Nanoribbons and the fabrication of patterned multilayer heterostructures. This low-damage, highly efficient manufacturing pathway directly addresses critical bottlenecks, paving the way for the commercialization of high-quality graphene devices.

This study presents a rapid, ambient, and scalable method for producing uniform, single-layer oxidized graphene (SOG) using 172 nm vacuum ultraviolet (VUV) irradiation from a xenon excimer (Xe-2) lamp. Compared to conventional UV/ozone oxidation requiring 6-10 min, the VUV process achieves comparable O/C (similar to 16%) and higher basal-plane uniformity in only 45 s at an irradiance of 18 mW/cm(2). Integrated spectroscopic analysis provides a detailed understanding of the chemical and structural properties of SOG. Raman spectroscopy reveals a high defect-related D peak intensity while the sharp single Lorentzian 2D peak remains preserved, indicating significant functionalization without the underlying graphene lattice integrity being compromised. Complementary X-ray photoelectron spectroscopy (XPS), supported by kinetic analysis, confirms the high chemical selectivity, showing that the SOG is predominantly functionalized with epoxy (C-O-C) groups while vacancy-like defects and unwanted carboxyl functionalities are minimized. Furthermore, large-area Raman mapping demonstrates that the oxidation proceeds with remarkable uniformity across the graphene basal plane, showing no preferential reaction at traditionally reactive sites such as edges or grain boundaries. This study establishes a robust photochemical route to a well-defined epoxy-rich graphene platform for developing advanced electronic applications.

Recent advancements in spiking neural networks (SNNs) have drawn inspiration from the human brain's distinctive capabilities, leading to significant impacts on various aspects of our lives and scientific endeavors. The development of hardware-based Spiking Neural Networks (H-SNNs) is a crucial aspect of the progress in neuromorphic computing, particularly in the context of on-chip implementations. H-SNNs involve the hardware realization of specific functionalities used in SNN algorithms, such as the leaky integrate-and-fire (LIF). One crucial functionality among these is neuronal homeostasis. However, although its importance in learning processes has been established, its hardware implementation at a single device remains unexplored until now. Here, we introduce a novel skyrmion-based spiking neuron device, which achieves hardware-level implementation of neuronal homeostasis. We have successfully demonstrated the modulation of a neuron's threshold value through gate voltage application, a major step forward in demonstrating the feasibility of neuronal homeostasis in a singular hardware unit. We believe that our findings have significant implications, not only for the development of advanced Spiking Neural Network (SNN)-based on-chip devices but also for the potential application of skyrmions in electronic devices.

Memristors based on 2D materials are promising for compact and energy‐efficient neuromorphic hardware. However, conventional devices require paired elements to implement bidirectional weight updates, such as spike‐timing‐dependent plasticity (STDP) and anti‐STDP for supervised spiking neural networks (SNN) such as the remote supervised method. Here, an Au/Ti/2D Sr 2 Nb 3 O 10 perovskite‐oxide nanosheet (SNO PON)/Pt memristor is demonstrated that exhibits dual bipolar resistive switching, supporting clockwise (interface) and counter‐clockwise (filament) switching. Ultrathin (≈5 nm) SNO PONs, fabricated over wafer‐scale areas by Langmuir–Blodgett deposition, serve as dynamic reservoirs for oxygen ions and vacancies. Voltage‐induced redox reactions at the Ti electrode are accompanied by the formation of oxygen vacancies in the SNO, as confirmed through cross‐sectional transmission electron microscopy and electron energy‐loss spectroscopy. The memristor exhibits stable resistance states with >10 3 s retention and <0.2 V set variation across 30 cells. Bidirectional plasticity under dual‐polarity pulse trains replicates STDP/anti‐STDP rules, enabling a 3 × 3 array to encode pixel patterns with opposite‐polarity pulses. A leaky integrate‐and‐fire SNN model achieves 86.4 % accuracy on the MNIST dataset using identical pre‐ and post‐synaptic spike waveforms. These findings establish dual bipolar 2D memristors as scalable and efficient components for high‐density, simplified supervised SNN hardware.

Multi-cation perovskite thin films are attracting significant research attention, owing to their unique physical properties. In particular, studies that provide insight into the microstructural properties and growth mechanisms of multi-cation Pb-based complex oxide thin films are highly desirable. The microstructural properties of Pbbased complex oxide thin films were studied using various transmission electron microscopy (TEM) techniques. The pyrochlore structure was elucidated by studying the atomic structure using HR (high -resolution) TEM, fast Fourier transform, and HR high -angle annular dark -field scanning transmission electron analyses. Additionally, the chemical properties of the multi-cation sites were characterized by energy-dispersive X-ray spectrometry, whereby the chemical composition of the pyrochlore structure was identified as Pb2(Nb0.56Zr0.77Ti0.67)O7 and that of the perovskite structure as Pb(Nb0.4Zr0.3Ti0.3)O3. The specific orientation relationship, [110]Pyrochlore//[010]Perovskite and (220)Pyrochlore//(100)Perovskite, was confirmed between the pyrochlore and perovskite structures at the bottom area of the layer. However, tilting of the pyrochlorestructured grains was frequently observed with increasing thickness. Finally, recovery of the interplanar spacings was observed in the perovskite and pyrochlore phases.

As there is an increasing need for an efficient solver of combinatorial optimization problems, much interest is paid to the Ising machine, which is a novel physics-driven computing system composed of coupled oscillators mimicking the dynamics of the system of coupled electronic spins. In this work, we propose an energy-efficient nano-oscillator, called OTSNO, which is composed of an Ovonic Threshold Switch (OTS) and an electrical resistor. We demonstrate that the OTSNO shows the synchronization behavior, an essential property for the realization of an Ising machine. Furthermore, we have discovered that the capacitive coupling is advantageous over the resistive coupling for the hardware implementation of an Ising solver by providing a larger margin of the variations of components. Finally, we implement an Ising machine composed of capacitively-coupled OTSNOs to demonstrate that the solution to a 14-node MaxCut problem can be obtained in 40 µs while consuming no more than 2.3 µJ of energy. Compared to a previous hardware implementation of the phase-transition nano-oscillator (PTNO)-based Ising machine, the OTSNO-based Ising machine in this work shows the performance of the increased speed by more than one order while consuming less energy by about an order.

Twisted bilayer graphene (tBLG) with small twist angles has attracted significant attention because of its unique electronic properties arising from the formation of a moiré superlattice. In this study, we systematically characterized the twist-angle-dependent electronic and transport properties of tBLG grown via chemical vapor deposition. This characterization included parameters such as the charge-neutral point voltage, carrier concentration, resistance, and mobility, covering a wide range of twist angles from 0° to 30°. We experimentally demonstrated that these parameters exhibited twist-angle-dependent moiré period trends, with high twist angles exceeding 9°, revealing more practically useful features, including improved mobilities compared to those of single-layer graphene. In addition, we demonstrated that the doping states and work functions were weakly dependent on the twist angles, as confirmed by additional first-principles calculations. This study provides valuable insights into the transport properties of tBLG and its potential for practical applications in the emerging field of twistronics.

Abstract A method for patterning single‐layer graphene (SLG) and single‐layer oxidized graphene (SOG) within a continuous atomic layer to form lateral heterojunctions is presented. Raman spectroscopy is employed to investigate the evolution of defect‐related Raman peaks during excimer‐UV irradiation, facilitating the identification of structural changes and defect formation processes. Electrical transport measurements reveal that SOG‐patterned field‐effect transistors (FETs) exhibit varying characteristics depending on the degree of oxidation, thus offering the potential to tailor the electrical properties of graphene devices for specific requirements. Scanning Kelvin probe microscopy measurements reveal the surface potential and work function of the SOG regions compared with those of SLG. The effective functionality of the SOG pattern to operate as a resistor, allowing control of the electrical conductivity in the SOG‐patterned SLG channels, is demonstrated. This capability restricts the current flow while preserving the pristine electrical properties of the graphene channel. Moreover, the SOG pattern can serve as a potential barrier to constructing SLG‐SOG‐patterned integrated circuits, providing exciting opportunities for engineering advanced electronic components. This breakthrough in graphene devices simplifies the fabrication process of graphene‐based FETs and provides the foundation for developing atomically thin integrated circuits for a wide range of applications.

Abstract Since the discovery of graphene and its remarkable properties, researchers have actively explored advanced graphene-patterning technologies. While the etching process is pivotal in shaping graphene channels, existing etching techniques have limitations such as low speed, high cost, residue contamination, and rough edges. Therefore, the development of facile and efficient etching methods is necessary. This study entailed the development of a novel technique for patterning graphene through dry etching, utilizing selective photochemical reactions precisely targeted at single-layer graphene (SLG) surfaces. This process is facilitated by an excimer ultraviolet lamp emitting light at a wavelength of 172 nm. The effectiveness of this technique in selectively removing SLG over large areas, leaving the few-layer graphene intact and clean, was confirmed by various spectroscopic analyses. Furthermore, we explored the application of this technique to device fabrication, revealing its potential to enhance the electrical properties of SLG-based devices. One-dimensional (1D) edge contacts fabricated using this method not only exhibited enhanced electrical transport characteristics compared to two-dimensional contact devices but also demonstrated enhanced efficiency in fabricating conventional 1D-contacted devices. This study addresses the demand for advanced technologies suitable for next-generation graphene devices, providing a promising and versatile graphene-patterning approach with broad applicability and high efficiency.

Two-dimensional (2D) synaptic devices based on charge trap/de-trap have attracted much attention due to their superior characteristics that is gate tunability, large switching ratio, long-term retention, and distinct synaptic potentiation/depression with low power. Here, we introduce a 2D Sr2-xCoxNb3O10 (SCNO) nanosheet layer between the MoS2 channel and SiO2 substrate because charge trap sites confined in SCNO nanosheet layer are anticipated to precisely control the 2D channel conductance. The hysteretic and synaptic behaviors of MoS2 channel can be controlled by charge trap/de-trap in two-dimensionally confined nanosheet layer with different doping ratio of Co. As the x value for the MoS2/SCNO field effect transistor (FET) increases, the shift of the threshold voltage (Vth) in a transfer curve increases and more linear potentiation/depression curves are induced with lower gate voltage pulse. In addition, paired-pulse facilitation is successfully implemented in a MoS2/SCNO FET. Therefore, our results suggest the feasibility of improved and efficient emulation of biological synaptic behavior in MoS2 transistors in contact with 2D oxide nanosheet layer.

We investigate magnetic properties of graphene oxide flake that have been locally oxidized using atomic force microscope (AFM) lithography. This approach reduces the possibility of magnetic contamination. Our Raman spectroscopy analysis reveals that the graphene oxide contains crystalline defects or disorders and differs from the pristine graphene in terms of its atomic structure. Using magnetic force microscopy measurements, we observe that the graphene oxide has a net magnetization pointing out of the surface plane. Furthermore, our magneto-optical Kerr effect data show small but clear hysteresis loops with non-zero remanent magnetization. We also conduct x-ray magnetic circular dichroism (XMCD) photoemission electron microscope measurements and identify remarkable asymmetry in carbon K edge spectra, which strongly suggests that the observed ferromagnetic order in the graphene oxide layer is intrinsic. A careful analysis of XMCD signals depending on the oxidized condition reveals the effects of chemical states of carbon atoms on the formation of ferromagnetic order in the graphene oxide.

The use of an identical electrolyte in electrochemical metallization (ECM)-based neuron and synaptic devices has not yet been achieved due to their different resistive-switching characteristics. Herein, we describe ECM devices comprising the same ferroelectric PbZr 0.52 Ti 0.48 O 3 (PZT) electrolyte, which can sustain both neuron and synaptic behavior depending on the identity of the active electrode. The Ag/PZT/La 0.8 Sr 0.2 MnO 3 (LSMO) threshold switching memristor shows abrupt and volatile resistive switching characteristics, which lead to neuron devices with stochastic integration-and-fire behavior, auto-recovery, and rapid operation. In contrast, the Ni/PZT/LSMO memory switching memristor exhibits gradual, non-volatile resistive switching behavior, which leads to synaptic devices with a high on/off ratio, low on-state current, low variability, and spike-timing-dependent plasticity (STDP). The divergent behavior of the ECM devices is attributed to greater control of cation migration through the ultrathin ferroelectric PZT. Thus, ECM devices with an identical ferroelectric electrolyte offer promise as essential building blocks in the construction of high-performance neuromorphic computing systems.

Solution-based processable high-k 2-dimensional (2D) ferroelectrics have attracted significant interest for use in next-generation nanoelectronics. Although few studies on potential 2D ferroelectric nanosheets in local areas have been conducted, reports on the thin-film characteristics applicable to the device are insufficient. In this study, we successfully synthesize high-k 2D Sr1.8Bi0.2Nan-3NbnO3n+1 (octahedral units, n = 3–5) nanosheets by the engineering of the n of NbO6 octahedral layers with A-site modification, and realized ferroelectric characteristics in ultrathin films (below 10 nm). The nanosheets are synthesized by a solution-based cation exchange process and deposited using the Langmuir-Blodgett (LB) method. As increasing the NbO6 octahedral layer, the thickness of the nanosheets increased and the band gaps are tuned to 3.80 eV (n = 3), 3.76 eV (n = 4), and 3.70 eV (n = 5). In addition, the dielectric permittivity of the 5-layer stacked nanofilm increase to 26 (n = 3), 33 (n = 4), and 62 (n = 5). In particular, the increased perovskite layer exhibits large distortions due to the size mismatch of Sr/Bi/Na ions at the A-site and promotes local ferroelectric instability due to its spontaneous polarization along the c-axis caused by an odd n number. We investigate the stable ferroelectricity in Pt/ 5-layer Sr1.8Bi0.2Na2Nb5O16 / Nb:STO capacitor by polarization-electric field (P-E) hysteresis; the coercive electric field (Ec) was 338 kV cm−1 and the remnant polarization (Pr) 2.36 μC cm−2. The ferroelectric properties of ultrathin 2D materials could drive interesting innovations in next-generation electronics.

Vertical two-terminal synaptic devices based on resistive switching have shown great potential for emulating biological signal processing and implementing artificial intelligence learning circuitries. To mimic heterosynaptic behaviors in vertical two-terminal synaptic devices, an additional terminal is required for neuromodulator activity. However, adding an extra terminal, such as a gate of the field-effect transistor, may lead to low scalability. In this study, a vertical two-terminal Pt/bilayer Sr1.8Ag0.2Nb3O10 (SANO) nanosheet/Nb:SrTiO3 (Nb:STO) device emulates heterosynaptic plasticity by controlling the number of trap sites in the SANO nanosheet via modulation of the tunneling current. Similar to biological neuromodulation, we modulated the synaptic plasticity, pulsed pair facilitation, and cutoff frequency of a simple two-terminal device. Therefore, our synaptic device can add high-level learning such as associative learning to a neuromorphic system with a simple cross-bar array structure.

Field-effect transistor-based biosensors have gained increasing interest due to their reactive surface to external stimuli and the adaptive feedback required for advanced sensing platforms in biohybrid neural interfaces. However, complex probing methods for surface functionalization remain a challenge that limits the industrial implementation of such devices. Herein, a simple, label-free biosensor based on molybdenum oxide (MoO3) with dopamine-regulated plasticity is demonstrated. Dopamine oxidation facilitated locally at the channel surface initiates a charge transfer mechanism between the molecule and the oxide, altering the channel conductance and successfully emulating the tunable synaptic weight by neurotransmitter activity. The oxygen level of the channel is shown to heavily affect the device's electrochemical properties, shifting from a nonreactive metallic characteristic to highly responsive semiconducting behavior. Controllable responsivity is achieved by optimizing the channel's dimension, which allows the devices to operate in wide ranges of dopamine concentration, from 100 nM to sub-mM levels, with excellent selectivity compared with K+, Na+, and Ca2+.

The paradigm shift of information carriers from charge to spin has long been awaited in modern electronics. The invention of the spin-information transistor is expected to be an essential building block for the future development of spintronics. Here, a proof-of-concept experiment of a magnetic skyrmion transistor working at room temperature, which has never been demonstrated experimentally, is introduced. With the spatially uniform control of magnetic anisotropy, the shape and topology of a skyrmion when passing the controlled area can be maintained. The findings will open a new route toward the design and realization of skyrmion-based spintronic devices in the near future.

In the era of “big data,” the cognitive system of the human brain is being mimicked through hardware implementation of highly accurate neuromorphic computing by progressive weight update in synaptic electronics. Low‐energy synaptic operation requires both low reading current and short operation time to be applicable to large‐scale neuromorphic computing systems. In this study, an energy‐efficient synaptic device is implemented comprising a Ni/Pb(Zr 0.52 Ti 0.48 )O 3 (PZT)/0.5 wt.% Nb‐doped SrTiO 3 (Nb:STO) heterojunction with a low reading current of 10 nA and short operation time of 20–100 ns. Ultralow femtojoule operation below 9 fJ at a synaptic event, which is comparable to the energy required for synaptic events in the human brain (10 fJ), is achieved by adjusting the Schottky barrier between the top electrode and ferroelectric film. Moreover, progressive domain switching in ferroelectric PZT successfully induces both low nonlinearity/asymmetry and good stability of the weight update. The synaptic device developed here can facilitate the development of large‐scale neuromorphic arrays for artificial neural networks with low energy consumption and high accuracy.