2D ultrathin oxides derived from liquid metals represent a unique class of 2D materials, offering low-temperature, scalable, and ambient-processable alternatives to conventional synthesis methods. Here, 2D ultrathin indium oxide (InOX) memtransistors are fabricated via a reproducible liquid-metal-printing process at 200 degrees C in ambient air, combining touch printing and blade coating. The resulting InOX films exhibit nanoscale thickness (similar to 4 nm), a wide optical bandgap (similar to 3.7 eV), and a polycrystalline, oxygen-deficient structure. Their intrinsically high conductivity is converted into stable semiconducting behavior through dry-air annealing. The fabricated memtransistors display robust, gate-tunable bipolar memristive switching with excellent endurance over 500 cycles and strong device-to-device uniformity. Notably, they achieve high switching ratios up to 103.63, outperforming most previously reported 2D memtransistors synthesized under high-temperature or vacuum conditions. The memristive behavior is governed by space-charge-limited conduction extending to the trap-filled limit, driven by carrier trapping/detrapping within exponentially distributed trap states. Moreover, the devices emulate synaptic plasticity and neuromodulation, achieving recognition accuracies up to 88.3% in artificial neural network simulations for handwritten image recognition. These results establish liquid-metal-printed ultrathin InOX as a promising, scalable platform for next-generation 2D neuromorphic and memory device technologies.

Multilayer transition metal dichalcogenides (ML-TMDs) with commensurate, incommensurate, and reconstructed structures, have emerged as a class of 2D materials with unique properties that differ significantly from their monolayer counterparts. While previous research has focused on monolayers, the discovery of various novel properties has sparked interest in multilayers with diverse structures engineered through stacking. These materials are characterized by interactions between layers and exhibit remarkable tunability in their structural, optical, and electronic behaviors depending on stacking order, twist angle, and interlayer coupling. This review provides an overview of ML-TMDs and explores their properties such as electronic band structure, optical responses, ferroelectricity, and anomalous Hall effect. Various synthetic methods employed to fabricate ML-TMDs, including mechanical stacking and chemical vapor deposition techniques, with an emphasis on achieving precise control of the twist angles and layer configurations, are discussed. This study further explores potential applications of ML-TMDs in nanoelectronics, optoelectronics, and quantum devices, where their unique properties can be harnessed for next-generation technologies. The critical role played by these materials in the development of future electronic and quantum devices is highlighted.

Technology for monitoring the concentration of high-concentration hydrogen gas, which is used as a fuel for hydrogen fuel cell vehicles, is urgently needed to be developed to maximize vehicle fuel efficiency. To improve the detection performance of the proton conductor-based hydrogen sensor, a membrane electrode assembly (MEA) consisting of a Nafion membrane and a Pt-C composite electrode was manufactured and applied to the hydrogen sensor. The hot press method was used to manufacture the MEA, and the junction characteristics were optimized by changing pressure, temperature, and time. The MEA was manufactured at a pressure range of 2–5 MPa, a temperature range of 40–80 °C, and a time range of 60–120 s, and the sheet resistance of the MEA was measured to investigate its dependence on the bonding process conditions. When the electrode-Nafion junction temperature and pressure were high, the MEA was stuck to the substrate or paper sheet and could not be separated into a discrete MEA. Additionally, when the temperature was low, the junction strength was insufficient, causing the Nafion and electrode to separate from each other. Through this study, it was confirmed that a robust and conductive MEA was obtained under optimal bonding conditions of 2 MPa, 60 °C, and 60 s, and the sensitivity of the hydrogen sensor was significantly improved.

Phase-change chalcogenide materials are extensively employedinvarious fields, particularly for electronic and optical applications.In this study, we demonstrated the optical property tuning of germaniumtelluride (GeTe) chalcogenide-ZrO2 nanocomposite filmsthrough microstructural modification using nanoparticle spin-coatingand thin film reflow. Pile-up features were observed in the case ofspin-coated ZrO2 nanoparticle nanocolloids, which optimizedthe higher spin speeds to enable the deposition of uniform and high-transmittanceZrO(2) nanoparticle layers. Additionally, the capillary-drivenmass transport at elevated temperatures resulted in the agglomerationand reflow of GeTe films, particularly in the near-eutectic compositionof GeTe(1:4) with reduced thickness. The morphological evolution ofthe GeTe films was used to fabricate nanocomposite films by sputterdepositing the films on spin-coated ZrO2 nanoparticle layers,followed by thermal annealing. The postannealing temperature was crucialfor controlling the transmittance, which primarily determined thecolor of the nanocomposite films. Different colored nanocompositefilms were obtained by adjusting the spin speed, GeTe thickness, andpostannealing temperature. The results indicated that the applicationof the developed nanocomposite films to semitransparent photovoltaicdevices increased the conversion efficiency owing to the light scatteringproperty of the films, in addition to improving the aesthetic appearance.

We demonstrate a high performance and cost effective cross point memory (CPM) technology for storage class memory(SCM) which consists of 20nm 1S1M (one selector one memory) unit cell for four-deck 256 Gb density. Novel process integration was developed to make a uniform Vt distribution for a sufficient read window margin (RWM) and a corresponding low raw bit error rate (RBER). However, in spite of the successful integration and excellent performances, it is expected that the scalability of the CPM will face the inevitable drawbacks such as severe thermal disturbance (TDB) and smaller write program margin which is due to the scaling limit of phase change memory component in CPM. Therefore SOM (selector only memory) is suggested as the alternative device for the next generation SCM.

Potentiometric oxygen sensors with excellent sensitivity in a low oxygen concentration range are designed based on intrinsic logarithmic response characteristics, and an asymmetric electrode structure, differentiated from conventional oxygen sensors with reference oxygen gases or parts exposed to air, is implemented. Electrolytes and electrode materials that formulate oxygen sensor devices are evaluated by comprehensively considering their reactivity to trace oxygen, oxygen ion formation, and ease of movement. The sensor using an yttria-stabilized zirconia bulk ceramic electrolyte measures the oxygen concentration in an oxygen-hydrogen mixture down to 0.5%, with a response time of 7.8 s. The sensor with a Nafion proton conductor film and a polyimide gas separation membrane allows room-temperature sensing and measures the oxygen concentration to a minimum of 2%.

The demand for hydrogen energy is rapidly increasing because of its clean, abundant, and efficient nature. To utilize hydrogen gas as a fuel for fuel‐cell vehicles, several types of hydrogen sensors are needed to address cost and safety issues. Precise monitoring of hydrogen gas concentration is critical in optimizing vehicle fuel‐cell efficiency. Herein, a fully packaged hydrogen sensor to continuously measure a hydrogen concentration of 20–100% with environmental variations is fabricated, including temperature (from −40 to 105 °C), humidity (from 10 to 98 RH%), and pressure (from 30 to 350 kPa). A signal‐processing circuit is designed to reduce the error rate, and a sensor chip and printed circuit board are assembled in a module using a packaging process with robust materials for harsh vehicle environments. The result herein suggests direct application of the sensor to monitor hydrogen concentration in the hydrogen recirculation unit in a fuel‐cell vehicle.

In this paper, we propose the structure of the 3D vertical cross point memory (3DVXP) having byte-addressability and discuss the possible challenges and requirements from the structural point of view. The necessity of a poly-Si vertical transistor for column selection and the feasibility of current drivability are presented. The structure driven parasitic resistance and capacitance problems on the device performances are discussed, and the resulting trade-off between the operation speed and the cell density is provided. We also demonstrate the advantage and the feasibility of the selectable memory, based on the memory-selector duality, for the application of 3DVXP.

This work reports on the fabrication of colored and translucent chalcogenide-oxide nanocomposite films, and their optical properties for use in transparent photoelectric device applications. Spin coating method from ZrO2 colloid solutions was used to deposit ZrO2 nanoparticle layers on substrates. GeTe chalcogenide thin films were subsequently deposited by rf sputtering, and were postannealed to form nanocomposite films. Color variation was achieved by the application of the nanocomposite films to glass substrates, which implies that the nanocomposite films can be applied to transparent photoelectric devices to improve aesthetic appearance by adjusting colors.

We developed an electro-thermal model for cross-point phase-change memory (X-PCM) and compared the calculation values with the experimental results. In order to simulate the electro-thermal phenomenon such as thermal disturbance (TDB) of victim cells and reset the current ( ${I}_{{\text {RESET}}}$ ) of aggressor cells in a fully confined cross-point structure, a three by three mini-array was constructed with the finite-elemental method. Unlike the conventional thermal model, which only shows the temperature gradient for TDB, our new model can predict the crystallization behavior of victim cells by combining the crystallization model for nucleation and growth. This makes it possible to compare the calculation results with the experimental ones through the crystalline fraction of the victim cell. The simulation results clearly reveal that our new model can closely estimate the victim cell’s crystalline fraction for TDB, with the variation of both pulse height (PH) and pulse width (PW) during the RESET operation. Applying the confirmed model for devices of smaller dimensions shows that TDB increases as the device scales down. The increase of TDB is particularly severe as cells become smaller than 16 nm. We suggest that TDB can be reduced not only by decreasing the thermal conductivity ( $\kappa $ ) of the interlayer dielectric (ILD), but also by minimizing the PW of the aggressor.

This paper reports the fabrication and characterization of a high-concentration potentiometric hydrogen sensor for fuel-cell vehicle applications. Hydrogen sensors have been mainly developed for detecting hydrogen at concentrations less than the lower explosion limit of 4% in air. However, a wide detection range is required to monitor and control hydrogen concentrations in hydrogen fuel-cell vehicles. We demonstrated a cost-effective and wide detection-range Nafion-based potentiometric hydrogen sensor. The conventional hot-pressing method was used to fabricate a small-sized and multilayer structure comprising a Nafion membrane and Pt-C electrodes. The dependence of the sensor performance on the hydrogen concentration, relative humidity, pressure, and temperature was examined. The fabricated sensor exhibited a response to hydrogen gas in a concentration range of 20–99.99% and a high performance reliability against environmental variations. The simple structure and reliable operation of the sensor make it promising for practical applications.

In this article, the development history and the technical hurdles of phase-change memory (PCM) are reviewed and recent progress and future directions are discussed. Prospects of PCM for storage-class memory (SCM) are discussed in terms of the technical challenges to satisfy the market requirements, mainly for the performance and cost effectiveness. For a more in-depth discussion, PCM is segmented into the memory part, the access device part, and the sensing scheme part. In the memory part, Set (crystallization)-Reset (amorphization) write characteristics and thermal disturbance (TDB) will be reinterpreted in terms of power consumption and performance of SCM. In the access device part, the application history of various devices, such as the transistor, the diode, and the two-terminal selector, will be reviewed and explained based on the process integration issues and area efficiency. In the next part, various sensing schemes used to make a lower read latency, multilevel cell (MLC), and cross point (X-point) are summarized. Thereafter, future directions and possible evolution pathways of 3-D structures, including X-point and vertical X-point (VXP), will be discussed for the first time. Finally, the feasibility of PCM for neuromorphic application will be followed.

We report the pulse dependent threshold voltage ( ${V} _{t}$ ) variation of the Ovonic Threshold Switch (OTS) and its effect on the read window margin (RWM) in Cross-Point Memory (XPM). We found that OTS ${V} _{t}$ varies by the height and width of the write-current pulse. The varied ${V} _{t}$ is persistently maintained even after 2E4 cycling of the write pulse, which means that the phenomenon is not a temporary one, but a type of memory effect in OTS itself. Therefore, it would affect the overall ${V} _{t}$ window ( $\Delta {V}_{t}$ ) of XPM by changing the Set ${V} _{t}$ ( ${V} _{t\_{}{\text {Set}}}$ ) and Reset ${V} _{t}$ ( ${V} _{t\_{}{\text {Reset}}}$ ) when combined with either phase-change memory (PCM) or resistive memory (RM). High-resolution transmission electron microscopy (HRTEM) and fast Fourier transform (FFT) images have proved that this phenomenon is not caused by the phase change of the OTS. Instead, a sub-threshold analysis extracted from the Poole-Frenkel model suggests that the phenomenon is associated with the variation of the amorphous network either by changes in the atomic bonding configuration or trap density.

This article describes the preparation of GeTe-based alloy films using a solution-based technique. The dissolution behavior of GeTe was initially examined by comparing the weight loss of GeTe powder in different solvents, and it was found that, unlike in the cases of n-butylamine and NH4OH, KOH fully dissolved GeTe to form an agglomerate-free solution. X-ray diffraction analysis revealed that the reaction between GeTe and KOH resulted in the formation of rhombohedral GeTe, cubic GeTe4, and hexagonal Te structures after drying. GeTe-based alloy films were then prepared by the spin coating of the GeTe-containing solutions on a silicon substrate. The surface morphology and reflectance properties of the prepared films were found to be highly dependent on the spin speed, with optimization of the spin coating parameter resulting in the deposition of a continuous and smooth film.

A bridge device is defined as a device that represents devices existing on the network but communicate using a bridged protocol rather than its own protocol in an IoT ecosystem. Bridged protocol means another protocol that is translated to or from the protocol the IoT ecosystem uses. In other words, the bridge device virtualizes IoT device in different IoT ecosystem into its own IoT ecosystem. In this paper we see how OCF bridge device virtualizes non-OCF devices into OCF ecosystem. BLE is used as a bridged protocol.