Photodoping plays an important role in determining the optoelectronic response of 2D semiconductor devices; however, the origin of the responsible trap states remains unclear. In this work, we investigate UV-induced photodoping in multilayer WSe2 field-effect transistors (FETs) based on WSe2/hBN heterostructures on SiO2/p-Si substrates. Wavelength-dependent measurements reveal pronounced n-type photodoping under 405 nm illumination, whereas the effect is orders of magnitude weaker under 640 nm excitation and for p-type photodoping. Furthermore, when the SiO2 layer is removed, both n-type and p-type photodoping are strongly suppressed, demonstrating that the oxide layer is essential for persistent photodoping. Analysis of defect-state distributions in amorphous SiO2, together with first-principles calculations for hBN defects, shows that the experimental observations cannot be explained by defects in hBN. Instead, the results indicate that defect states in the SiO2 substrate act as charge reservoirs that facilitate charge transfer and long-term carrier trapping. These findings highlight the dominant role of substrate-related trap states in UV-induced photodoping and photogating behavior in WSe2 FET devices.

Two-dimensional Ruddlesden-Popper lead halide perovskites (2D-RPPs) are promising materials for solar cells and photovoltaic devices and their device stability is significantly improved compared to three-dimensional perovskites due to increased hydrophobicity and suppressed ion transport. However, 2D-RPPs are also known to be susceptible to moisture and light, which leads to rapid degradation and thus limits their direct applications. Recent research has focused on blocking degradation factors using insulating layers such as poly(methyl methacrylate) or hexagonal boron nitride (hBN). However, most studies have concentrated on blocking the effects of oxygen and moisture and examining their effects. In this study, we performed passivation with hBN flakes and placed silica gel in a vacuum desiccator to minimize the effects of oxygen and moisture. We then analyzed the differences in the effects on illumination depending on the hBN thickness.

ABSTRACT Ferroelectric metal nitride thin films, particularly AlScN, have recently emerged as transformative materials for next‐generation electronics, owing to their high polarization, tunable coercive fields, exceptional endurance, and thermal stability. In pursuit of device miniaturization, atomic layer deposition (ALD) offers unparalleled advantages by delivering angstrom‐level thickness precision and conformality on complex 3D architectures; yet most prior studies have relied on physical vapor deposition of films several hundred nanometers thick. Here, we demonstrate the plasma‐enhanced ALD of B‐doped AlN (AlBN) thin films, where systematic control of the AlN:BN cycle ratio precisely regulates B concentration, enabling direct elucidation of the interplay between composition, crystallinity, and ferroelectric behavior. Density functional theory provided mechanistic insight into B incorporation pathways, while piezoresponse force microscopy confirmed local polarization switching across all compositions, with the optimized AlBN film exhibiting the most pronounced P–E hysteresis loop. This composition further displayed low leakage current and endurance exceeding 10 5 switching cycles. Collectively, these findings establish PEALD‐grown AlBN as a robust ferroelectric nitride and highlight its promise as a CMOS‐compatible, scalable alternative to AlScN for next‐generation non‐volatile memory technologies.

In this study, we demonstrated a multiresistive state memristor with UV-ozone-treated two-dimensional semiconductor MoS2 to realize resistive switching. A lateral junction of the MoS2 and MoOx memristor was prepared by selectively oxidizing a portion of the MoS2 surface. Memristive properties were investigated following the confirmation of MoOx formation on the MoS2 surface via optical and electrical characterization. These properties included multiresistive state behavior dependent on the voltage sweep range, low resistance state current level twice that of the high resistance state, and robust stability (similar to 5000 s). Consequently, the potential for developing a two-dimensional, oxide-based memristor is presented based on an analysis of the voltage-current relationship and proposed switching mechanism of the MoS2-MoOx junction.

In the era of artificial intelligence (AI) and big data, low-energy devices are essential for minimizing both energy consumption and heat generation. This study introduces an ultralow-energy memory featuring an oxidized boron nitride (OBN)-based charge trap layer, fabricated through a simple ultraviolet (UV)-O3 exposure treatment of hexagonal boron nitride (hBN) in two-dimensional material heterostructures. A thorough examination of the oxygen bonding type on the hBN surface during UV-O3 exposure confirms bandgap closure and an increase in trap densities as the material transitions from hBN to OBN. Additionally, the composition and properties of OBN are investigated and its charge-trapping capability is validated due to the increase in trap states. Consequently, we fabricate WS2/OBN/hBN/graphene heterostructures and demonstrate an ultra-low energy memory system, achieving exceptionally low energy consumption at the zepto-joule scale (-6 x10- 20 J) with a pulse duration of 20 ns.

α-In2Se3 semiconductor crystals realize artificial synapses by tuning in-plane and out-of-plane ferroelectricity with diverse avenues of electrical and optical pulses. While the electrically induced ferroelectricity of α-In2Se3 shows synaptic memory operation, the optically assisted synaptic plasticity in α-In2Se3 has also been preferred for polarization flipping enhancement. Here, the synaptic memory behavior of α-In2Se3 is demonstrated by applying electrical gate voltages under white light. As a result, the induced internal electric field is identified at a polarization flipped conductance channel in α-In2Se3/hexagonal boron nitride (hBN) heterostructure ferroelectric field effect transistors (FeFETs) under white light and discuss the contribution of this built-in electric field on synapse characterization. The biased dipoles in α-In2Se3 toward potentiation polarization direction by an enhanced internal built-in electric field under illumination of white light lead to improvement of linearity for long-term depression curves with proper electric spikes. Consequently, upon applying appropriate electric spikes to α-In2Se3/hBN FeFETs with illuminating white light, the recognition accuracy values significantly through the artificial learning simulation is elevated for discriminating hand-written digit number images.

Photo-Stimulated Ferroelectric Memories In article number 2307346, Kanghoon Yim, Young-Jun Yu, and co-workers demonstrate white-light illuminated α-In2Se3 ferroelectric field effect transistors for efficient synaptic memory operation. By spontaneous Fermi level regulation of α-In2Se3 with photogenerated electron-hole pairs, the strengthened built-in electric field within an α-In2Se3 channel allows the superior recognition accuracy of artificial neural networks. This advancement could be invaluable in the forthcoming era of artificial neuromorphic computing.

Memristors based on silver iodide (AgI), a solid-state electrolyte, with resistive switching are favored in artificial neural networks. In this study, high light transmittance of AgI was confirmed through the iodization of Ag using a vapor-phase iodization method. In addition, using transparent multi-layered graphene (MLG) as the electrode, an MLG/AgI/MLG structure was fabricated, with observations of its resistive memory switching and threshold switching characteristics measured to assess the possibility of application in a memory device and a selector, respectively. The findings here present the possibility of the use of AgI in highly transparent electronic devices for multiple uses.

In this report, we introduce a scanning gate microscope (SGM) to characterize nanoscale conductive channels under dielectric materials. We comprehensively review the electrical characterization of a graphene nanoribbon (GNR) using the SGM. We present a method to measure partial electrical gating on GNR via an SGM probe. Furthermore, by employing the assumption of GNR width difference for the partial position of the GNR, we attempt to elucidate the conductance distribution on the GNR by partial gating.

Hot electron photodetection provides a powerful platform for photosensing beyond the bandgap of a semiconductor. High‐performing hot electron photodetection has been reported in 2D transition metal dichalcogenide material‐based devices without the support of plasmonic metal nanostructures but with planar metal electrodes. However, the mechanism driving hot electron dynamics in 2D transition metal dichalcogenide devices has not been explored. Here, we uncover the hot electron transfer in MoS 2 and Pt van der Waals (vdW) metal electrodes by transient reflection spectroscopy, revealing a sub‐picosecond transfer time of hot electron and a decelerated recombination process in MoS 2 at the below bandgap photoexcitation compared to the pristine MoS 2 . With an independent photocurrent mapping, the ultralong diffusion is revealed in MoS 2 /vdW metal electrode and a self‐powered near‐infrared (NIR) photodetector is demonstrated with a high responsivity of 6 mA W −1 and detectivity of 9 × 10 9 Jones at a wavelength of 1062 nm by integrating Pt and Ag asymmetric vdW electrodes into MoS 2 . The results will pave the way for the next generation of hot‐electron‐based self‐powered optoelectronic devices.

Resistive random-access memory (ReRAM), an alternative to conventional charge storage memory, employs the switching of a resistive material between high-resistance and low-resistance states, which can be generated by the formation/dissolution of metal filaments bridging the two electrodes in the cell. Silver iodide (AgI) is a promising solid electrolyte for ReRAM cells, but its application is hindered by poor photostability and low electrical conductivity. Herein, a Cu-substituted beta-AgI system, beta'-Ag0.7Cu0.3I, was successfully prepared via sequential deposition of a Cu metal layer onto a AgI thin film by a galvanic reaction, which induced the spontaneous incorporation of Cu+ cations into the AgI lattice. Cu substitution at the Cu-AgI heterojunction interface is a novel way to modulate the chemical composition and improve the resistive switching properties of intrinsic polycrystalline AgI thin films. We compared the resistive switching properties of a ReRAM thin film devices based on beta'-Ag0.7Cu0.3I with those based on pristine beta-AgI. This device exhibited enhanced performance with high ON/OFF ratio (similar to 10(4)) and low working voltage compared with the beta-AgI-based device. These results strongly suggest that binary metal halide materials can serve as simple model systems for the efficient formation of metal filaments and have potential low-cost, low-power memory applications.

We fabricated Graphene Oxide (GO) sandwiched by Multi-layer Graphene (MLG) for operating as an RRAM device. By investigating the UV-O-3 treatment time dependency of the MLG/GO/MLG device, we confirmed the critical UV-O-3 treatment time under sufficiently oxidized conditions for stable Resistive Random Access Memory (RRAM) operation during a repeating DC voltage sweep. The bipolar resistive switching mechanism of the MLG/GO/MLG structure was verified through the algebraic algorithmic relation between the current and voltage. This result provides important clues for developing fully 2D material-based electric devices.

Solar radiation, especially the UV-A light rays (320-400 nm) exposure causes severe health hazard such as skinrelated cancer and premature aging. Owing to the significance of UV-A photodetection, a high-performance UV-A photodetectors (PD) with high sensitivity, large detectivity and fast response time, have attracted great attention in various optoelectronic applications. Herein, we report a self-powered (SP) UV PD based on Pt nanoparticles (NP) decorated TiO2/GaN nanorods (NRs) hybrid heterojunction. The proposed Pt NP@TiO2/GaN NRs hybrid device demonstrates pronounced photoelectric performances including a large responsivity (44.6 A/W), superior detectivity (1.57 x 1014 Jones) and high electronic quantum efficiency (8.65 x 103 %) under the UV light intensity (lambda = 382 nm, 1.32 mW/cm2) at zero bias, which are relatively much higher as compare to the pristine counterparts. In addition, the hybrid PD showed a short response/recovery times of 180 ms/200 ms, with a remarkable reproducibility and long-term stability towards the UV light. The impressive photoresponse properties of the hybrid SP PD are ascribed to the large photon absorption endorsed by the localized surface plasmonic resonance effect of Pt NP and the adequate built-in potential at the TiO2 and GaN NRs heterojunction interface, which further endows the effective separation and transport of photogenerated charge carriers. Furthermore, the plausible mechanism for the high-performances of hybrid UV PD is demonstrated in detailed using the energy band diagram. Our work reveals that the integral advantages of hybrid heterostructures, have a significant potential for the practical applications of advanced optoelectronics and high-performance SP UV-A PD.

Unintentional bubbles are formed when manufacturing devices using two-dimensional materials. Usually, these bubbles affect device perfor-mance degradation, but in the case of memory devices, an additional charge trap can be expected. We investigate the direct surface potential of bubbles formed in a hexagonal boron nitride (hBN)/multilayer graphene (MLG) heterostructure. Specifically, we study the electron transfer improvement by increasing the memory window of a MoS2/hBN/MLG heterostructure in floating gate memory owing to bubbles formed at the hBN/MLG heterointerface. This characterization of bubbles containing molecules such as water or hydrocarbon in two-dimensional material heterointerfaces can promote the understanding of charge carrier tunneling in two-dimensional material heterostructures.

In this work, we develop a gate-tunable gas sensor based on a MoS2/hBN heterostructure field effect transistor. Through experimental measurements and numerical simulations, we systematically reveal a principle that relates the concentration of the target gas and sensing signals (ΔI/I0) as a function of gate bias. Because a linear relationship between ΔI/I0 and the gas concentration guarantees reliable sensor operation, the optimal gate bias condition for linearity was investigated. Taking NO2 and NH3 as target molecules, it is clarified that the bias condition greatly depends on the electron accepting/donating nature of the gas. The effects of the bandgap and polarity of the transition metal dichalcogenides (TMDC) channel are also discussed. In order to achieve linearly increasing signals that are stable with respect to the gas concentration, a sufficiently large VBG within VBG > 0 is required. We expect this work will shed light on a way to precisely design reliable semiconducting gas sensors based on the characteristics of TMDC and target gas molecules.

In this study, we investigated the redox process occurring on graphene with an H 2 SO 4 electrolyte gating.The redox process occurring on graphene was studied by observing the variation in the conductance of graphene.By performing electric force microscopy measurements, we also observed the surface condition of graphene leading oxidation and its role as a seed for adsorbing undesired residues, which results in conductance suppression.

In this work, oxidized black phosphorus (BP) was trapped in the top and bottom interfaces of graphite thin film electrodes by hexagonal boron nitride (hBN) encapsulation.Upon using partial encapsulation of hBN on BP, the oxidation of bare BP area led to the oxidation of hBN encapsulated whole BP, and this oxidized BP could be confined in the hBN layer.Furthermore, by attaching graphite thin film electrodes on and underneath the oxidized BP layer, charge carrier injection and extraction behavior from measuring the current tunneling was characterized by applying a bias voltage between the top and the bottom graphite thin film electrodes.The electrical characteristics according to applied bias voltage was confirmed with a double log plot.It was found that the ohmic current region exists in the low voltage state, and the space-chargelimited conduction region exists in the high voltage state.

Van der Waals (vdW) heterostructures with 2D materials have shown that atomically thin non-volatile memories are advantageous in terms of integration, while offering high performance and excellent stability. The non-volatile memory behavior of 2D materials has mainly been studied for single-bit operation, and there is growing interest in expanding to multi-bit operation to enhance the storage capacities of memory devices. However, the conditions or rules for generating the desired number of bits in 2D-based multi-bit memory remain to be identified. In this study, multiple bits are successfully created on non-volatile memory based on vdW heterostructure floating-gate memory (FGM) by systematically tuning the dimensions of the 2D materials. In particular, a fingerprint mechanism is established that links the bit number and dimensions of 2D crystals on vdW heterostructures. This approach could enable the precise generation of the desired number of bits in layered-material-based vdW FGMs.

Here, a graphene nanoribbon (GNR) field-effect transistor (FET), which includes an initial electrical defect on the GNR channel, is studied via electrical transport and scanning thermal microscope (SThM) measurements. That the spatial temperature distribution for a Joule self-heated GNR FET could be directly investigated before and after the breakdown condition. This method for investigating failures in a GNR channel will allow us to diagnose the quality of nanoscale graphene.

In this work, we investigated the variation in surface conditions of graphene by employing atomic force microscopy and optical images.We inspected the resistance and doping at selected areas of graphene by transport measurements.Especially, the area with a dominant contribution from the edges, which have more disorders and poly (methyl methacrylate) residues compared to the central surface of graphene, showed large resistance as well as large doping concentration.Our study facilitated the understanding of the electric conditions on graphene surface and edge areas.