Low‐Power Nonvolatile Charge Storage Memory Based on MoS2 and an Ultrathin Polymer Tunneling Dielectric

Low‐power, nonvolatile memory is an essential electronic component to store and process the unprecedented data flood arising from the oncoming Internet of Things era. Molybdenum disulfide (MoS₂) is a 2D material that is increasingly regarded as a promising semiconductor material in electronic device applications because of its unique physical characteristics. However, dielectric formation of an ultrathin low‐k tunneling on the dangling bond‐free surface of MoS₂ is a challenging task. Here, MoS₂‐based low‐power nonvolatile charge storage memory devices are reported with a poly(1,3,5‐trimethyl‐1,3,5‐trivinyl cyclotrisiloxane) (pV3D3) tunneling dielectric layer formed via a solvent‐free initiated chemical vapor deposition (iCVD) process. The surface‐growing polymerization and low‐temperature nature of the iCVD process enable the conformal growing of low‐k (≈2.2) pV3D3 insulating films on MoS₂. The fabricated memory devices exhibit a tunable memory window with high on/off ratio (≈10⁶), excellent retention times of 10⁵ s with an extrapolated time of possibly years, and an excellent cycling endurance of more than 10³ cycles, which are much higher than those reported previously for MoS₂‐based memory devices. By leveraging the inherent flexibility of both MoS₂ and polymer dielectric films, this research presents an important milestone in the development of low‐power flexible nonvolatile memory devices.     

Systematic Design and Demonstration of Multi-Bit Generation in Layered Materials Heterostructures Floating-Gate Memory

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.     

A Die‐Selection Method Using Search‐Space Conditions for Yield Enhancement in 3D Memory

Three‐dimensional (3D) memories using through‐silicon vias (TSVs) as vertical buses across memory layers will likely be the first commercial application of 3D integrated circuit technology. The memory dies to stack together in a 3D memory are selected by a die‐selection method. The conventional die‐selection methods do not result in a high‐enough yields of 3D memories because 3D memories are typically composed of known‐good‐dies (KGDs), which are repaired using self‐contained redundancies. In 3D memory, redundancy sharing between neighboring vertical memory dies using TSVs is an effective strategy for yield enhancement. With the redundancy sharing strategy, a known‐bad‐die (KBD) possibly becomes a KGD after bonding. In this paper, we propose a novel die‐selection method using KBDs as well as KGDs for yield enhancement in 3D memory. The proposed die‐selection method uses three search‐space conditions, which can reduce the search space for selecting memory dies to manufacture 3D memories. Simulation results show that the proposed die‐selection method can significantly improve the yield of 3D memories in various fault distributions.     

Simultaneous Tenfold Brightness Enhancement and Emitted‐Light Spectral Tunability in Transparent Ambipolar Organic Light‐Emitting Transistor by Integration of High‐k Photonic Crystal

In organic light‐emitting transistors, the structural properties such as the in‐plane geometry and the lateral charge injection are the key elements that enable the monolithic integration of multiple electronic, optoelectronic, and photonic functions within the same device. Here, the realization of highly integrated multifunctional optoelectronic organic device is reported by introducing a high‐capacitance photonic crystal as a gate dielectric into a transparent single‐layer ambipolar organic light‐emitting transistor (OLET). By engineering the photonic crystal multistack and bandgap, it is showed that the integration of the photonic structure has a twofold effect on the optoelectronic performance of the device, i.e., i) to modulate the spectral profile and outcoupling of the emitted light and ii) to enhance the transistor source–drain current by a 25‐fold factor. Consequently, the photonic‐crystal‐integrated OLET shows an order of magnitude higher emitted power and brightness with respect to the corresponding polymer‐dielectric device, while presenting as‐designed electroluminescence spectral and spatial distribution. The results validate the efficacy of the proposed approach that is expected to unravel the technological potential for the realization of highly integrated optoelectronic smart systems based on organic light‐emitting transistors.     

Carrier Type Control of WSe2 Field‐Effect Transistors by Thickness Modulation and MoO3 Layer Doping

Control of the carrier type in 2D materials is critical for realizing complementary logic computation. Carrier type control in WSe₂ field‐effect transistors (FETs) is presented via thickness engineering and solid‐state oxide doping, which are compatible with state‐of‐the‐art integrated circuit (IC) processing. It is found that the carrier type of WSe₂ FETs evolves with its thickness, namely, p‐type (<4 nm), ambipolar (≈6 nm), and n‐type (>15 nm). This layer‐dependent carrier type can be understood as a result of drastic change of the band edge of WSe₂ as a function of the thickness and their band offsets to the metal contacts. The strong carrier type tuning by solid‐state oxide doping is also demonstrated, in which ambipolar characteristics of WSe₂ FETs are converted into pure p‐type, and the field‐effect hole mobility is enhanced by two orders of magnitude. The studies not only provide IC‐compatible processing method to control the carrier type in 2D semiconductor, but also enable to build functional devices, such as, a tunable diode formed with an asymmetrical‐thick WSe₂ flake for fast photodetectors.     

2D Hybrid Perovskite Ferroelectric Enables Highly Sensitive X‐Ray Detection with Low Driving Voltage

X‐ray detectors with high sensitivity are of great significance in both civil and military fields. Over the past decades, great efforts have been made to improve the sensitivity in conventional inorganic materials, but mainly at the cost of increasing the energy consumption with a quite high operating voltage. Developing photosensitive ferroelectrics directly as detector materials may be a conceptually new strategy in view of the strong ferroelectric spontaneous polarization (P_s) that assists photoinduced carriers separation and transport. A high‐performance X‐ray detector in 2D hybrid halide perovskite ferroelectric (C₄H₉NH₃)₂(C₂H₅NH₃)₂Pb₃Br₁₀ ( BA₂EA₂Pb₃Br₁₀ ) (P_s = 5 µC cm^?2) is fabricated and exhibits an ultrahigh X‐ray sensitivity up to 6.8 × 10³ µC Gy_air^?1 cm^?2 even at a relatively low operating voltage, which is over 300‐fold larger than that of state‐of‐the‐art α‐Se X‐ray detectors. Such a brilliant figure‐of‐merit is largely attributed to the superior mobility–lifetime products associated with the strong ferroelectric polarization of BA₂EA₂Pb₃Br₁₀ . As pioneering work, these findings inform the exploration of hybrid halide perovskite ferroelectrics toward high‐performance photoelectronic devices.     

Printed,Flexible, Organic Nano‐Floating‐Gate Memory: Effects of Metal Nanoparticles and Blocking Dielectrics on Memory Characteristics

The effects of using a blocking dielectric layer and metal nanoparticles (NPs) as charge‐trapping sites on the characteristics of organic nano‐floating‐gate memory (NFGM) devices are investigated. High‐performance NFGM devices are fabricated using the n‐type polymer semiconductor, poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2)), and various metal NPs. These NPs are embedded within bilayers of various polymer dielectrics (polystyrene (PS)/poly(4‐vinyl phenol) (PVP) and PS/poly(methyl methacrylate) (PMMA)). The P(NDI2OD‐T2) organic field‐effect transistor (OFET)‐based NFGM devices exhibit high electron mobilities (0.4–0.5 cm² V^?1 s^?1) and reliable non‐volatile memory characteristics, which include a wide memory window (≈52 V), a high on/off‐current ratio (I_on/I_off ≈ 10⁵), and a long extrapolated retention time (>10⁷ s), depending on the choice of the blocking dielectric (PVP or PMMA) and the metal (Au, Ag, Cu, or Al) NPs. The best memory characteristics are achieved in the ones fabricated using PMMA and Au or Ag NPs. The NFGM devices with PMMA and spatially well‐distributed Cu NPs show quasi‐permanent retention characteristics. An inkjet‐printed flexible P(NDI2OD‐T2) 256‐bit transistor memory array (16 × 16 transistors) with Au‐NPs on a polyethylene naphthalate substrate is also fabricated. These memory devices in array exhibit a high I_on/I_off (≈10^{4 ± 0.85}), wide memory window (≈43.5 V ± 8.3 V), and a high degree of reliability.     

2D Single‐Crystalline Molecular Semiconductors with Precise Layer Definition Achieved by Floating‐Coffee‐Ring‐Driven Assembly

2D organic materials with in‐plane van der Waals forces among molecules have unique characteristics that ensure a brilliant future for multifunctional applications. Soluble organic semiconductors can be used to achieve low‐cost and high‐throughput manufacturing of electronic devices. However, achieving solution‐processed 2D single‐crystalline semiconductors with uniform morphology remains a substantial challenge. Here, the fabrication of 2D molecular single‐crystal semiconductors with precise layer definition by using a floating‐coffee‐ring‐driven assembly is presented. In particular, bilayer molecular films exhibit single‐crystalline features with atomic smoothness and high film uniformity over a large area; field‐effect transistors yield average and maximum carrier mobilities of 4.8 and 13.0 cm² V^?1 s^?1, respectively. This work demonstrates the strong potential of 2D molecular crystals for low‐cost, large‐area, and high‐performance electronics.     

Magnetic Field‐Induced Phase Transformation in NiMnCoIn Magnetic Shape‐Memory Alloys—A New Actuation Mechanism with Large Work Output

Magnetic shape memory alloys (MSMAs) have recently been developed into a new class of functional materials that are capable of magnetic‐field‐induced actuation, mechanical sensing, magnetic refrigeration, and energy harvesting. In the present work, the magnetic &!hyphen;field‐induced martensitic phase transformation (FIPT) in Ni₄₅Mn_36.5Co₅In_13.5 MSMA single crystals is characterized as a new actuation mechanism with potential to result in ultra‐high actuation work outputs. The effects of the applied magnetic field on the transformation temperatures, magnetization, and superelastic response are investigated. The magnetic work output of NiMnCoIn alloys is determined to be more than 1 MJ m^?3 per Tesla, which is one order of magnitude higher than that of the most well‐known MSMAs, i.e., NiMnGa alloys. In addition, the work output of NiMnCoIn alloys is orientation independent, potentially surpassing the need for single crystals, and not limited by a saturation magnetic field, as opposed to NiMnGa MSMAs. Experimental and theoretical transformation strains and magnetostress levels are determined as a function of crystal orientation. It is found that [111]‐oriented crystals can demonstrate a magnetostress level of 140 MPa T^?1 with 1.2% axial strain under compression. These field‐induced stress and strain levels are significantly higher than those from existing piezoelectric and magnetostrictive actuators. A thermodynamical framework is introduced to comprehend the magnetic energy contributions during FIPT. The present work reveals that the magnetic FIPT mechanism is promising for magnetic actuation applications and provides new opportunities for applications requiring high actuation work‐outputs with relatively large actuation frequencies. One potential issue is the requirement for relatively high critical magnetic fields and field intervals (1.5–3 T) for the onset of FIPT and for reversible FIPT, respectively.     

A High‐Performance Nitro‐Explosives Schottky Sensor Boosted by Interface Modulation

A high‐performance Schottky sensor boosted by interface modulation is fabricated for the detection of trace nitro‐explosives vapors. The interface modulation strategy results in a silicon nanowires (SiNWs) array/TiO₂/reduced graphene oxide (rGO) sensor with sensitive and selective response toward nitro‐explosives vapors. The response of the SiNWs array/TiO₂/rGO sensor toward nitro‐explosives vapors, such as 9 ppb 2,4,6‐trinitrotoluene, 4.9 ppt hexogen, and 0.25 ppq octagon, is boosted by 2.4, 7.5, and 5 times with the insertion of TiO₂. Superior selectivity is shown even compared with interfering gases of 10 ppm. Such good sensing performance can be attributed to the good sensing performance of the Schottky heterojunction‐based sensor, the Schottky barrier height modulation with the insertion of TiO₂, SiNWs array structure enhanced diffusion, and TiO₂ nanoparticles enhanced adsorption. This is believed to be the first Schottky heterojunction‐based sensor for nitro‐explosives vapors detection. This work would open a new way to develop highly sensitive and selective sensors.     

A Multibeam Interference Model for Analyzing Complex Near‐Field Images of Polaritons in 2D van der Waals Microstructures

Van der Waals (vdW) materials are among the most promising candidates for photonic integrated circuits because they support a full set of polaritons that can manipulate light at deep subdiffraction nanoscale. It is possible to directly probe the propagating polaritons in vdW materials in real space via scattering‐type scanning near‐field optical microscopy, such that the wave vector and lifetime of the polaritons can be extracted from as‐measured interference fringes by Fourier analysis. However, this method is unsuitable for clutter interference patterns in samples exhibiting inadequate fringes due to small size (less than 10 µm) or complex edges that are often encountered in nanophotonic devices and new material characterization. Here, a multibeam interference model is developed to analyze complex images by disentangling them into periodic patterns and residue. By employing phase stationary approximation, polariton wave vector can be derived from offset ratio of the center point, and the ratio of polariton reflection and scattering rates at the edge is obtained from the ratio of the periodic and aperiodic patterns. This method can be widely used in the optical characterization of new vdW materials that are difficult to synthesize into large crystals, as well as nanophotonic integrated devices with unique boundaries.     

Simulation and Fabrication Studies of Semi‐superjunction Trench Power MOSFETs by RSO Process with Silicon Nitride Layer

In this letter, we propose a new RESURF stepped oxide (RSO) process to make a semi‐superjunction (semi‐SJ) trench double‐diffused MOSFET (TDMOS). In this new process, the thick single insulation layer (SiO₂) of a conventional device is replaced by a multilayered insulator (SiO₂/SiN_x/TEOS) to improve the process and electrical properties. To compare the electrical properties of the conventional RSO TDMOS to those of the proposed TDMOS, that is, the nitride_RSO TDMOS, simulation studies are performed using a TCAD simulator. The nitride_RSO TDMOS has superior properties compared to those of the RSO TDMOS, in terms of drain current and on‐resistance, owing to a high nitride permittivity. Moreover, variations in the electrical properties of the nitride_RSO TDMOS are investigated using various devices, pitch sizes, and thicknesses of the insulator. Along with an increase of the device pitch size and the thickness of the insulator, the breakdown voltage slowly improves due to a vertical field plate effect; however, the drain current and on‐resistance degenerate, owing to a shrinking of the drift width. The nitride_RSO TDMOS is successfully fabricated, and the blocking voltage and specific on‐resistance are 108 V and 1.1 mΩcm², respectively.     

All‐Layered 2D Optoelectronics: A High‐Performance UV–vis–NIR Broadband SnSe Photodetector with Bi2Te3 Topological Insulator Electrodes

Nanoelectronics is in urgent demand of exceptional device architecture with ultrathin thickness below 10 nm and dangling‐bond‐free surface to break through current physical bottleneck and achieve new record of integration level. The advance in 2D van der Waals materials endows scientists with new accessibility. This study reports an all‐layered 2D Bi₂Te₃‐SnSe‐Bi₂Te₃ photodetector, and the broadband photoresponse of the device from ultraviolet (370 nm) to near‐infrared (808 nm) is demonstrated. In addition, the optimized responsivity reaches 5.5 A W^?1, with the corresponding eternal quantum efficiency of 1833% and detectivity of 6 × 10¹⁰ cm Hz^1/2 W^?1. These figures‐of‐merits are among the best values of the reported all‐layered 2D photodetectors, which are several orders of magnitude higher than those of the previous SnSe photodetectors. The superior device performance is attributed to the synergy of highly conductive surface state of Bi₂Te₃ topological insulator, perfect band alignment between Bi₂Te₃ and SnSe as well as small interface potential fluctuation. Meanwhile, the all‐layered 2D device is further constructed onto flexible mica substrate and its photoresponse is maintained roughly unchanged upon 60 bending cycles. The findings represent a fundamental scenario for advancement of the next generation high performance and high integration level flexible optoelectronics.     

Topology Optimization‐Based Inverse Design of Plasmonic Nanodimer with Maximum Near‐Field Enhancement

The near‐field enhancement factor is one of the most significant parameters to evaluate the performance of plasmonic nanostructures. Numerous efforts have been made to maximize the enhancement factor through optimizing the size, shape, and spatial arrangement of metallic nanostructures with simple geometries, such as disk, triangle, and rod. This work implements topology optimization to inversely design a metallic nanoparticle dimer with the goal of optimizing the near‐field enhancement factor in its sub‐10 nm gap. By optimizing the material layout within a given design space, the topology optimization algorithm results in a plasmonic nanodimer of two heart‐shaped particles having both convex and concave features. Full‐wave electromagnetic analysis reveals that the largest near‐field enhancement in the heart‐shaped nanoparticle dimer is originated from the greatest concentration of surface charges at the nano‐heart apex. Inversely designed heart‐, bowtie‐, and disk‐shaped nanodimers are fabricated by using focused helium ion beam milling with a “sketch and peel” strategy, and their near‐field enhancement performances are characterized with nonlinear optical spectroscopies at the single‐particle level. Indeed, the heart‐shaped nanodimer exhibits much stronger signal intensities than the other two structures. The present work corroborates the validity and effectiveness of topology optimization‐based inverse design in achieving desired plasmonic functionalities.     

The First 2D Hybrid Perovskite Ferroelectric Showing Broadband White‐Light Emission with High Color Rendering Index

Luminescent ferroelectrics have attracted considerable attention in terms of integrated photoelectronic devices, most of which are focused on the multicomponent systems of rare‐earth doping ferroelectric ceramics. However, bulk ferroelectricity with coexistence of strong white‐light emission, especially in the single‐component system, remains quite rare. Here, a new organic–inorganic hybrid ferroelectric of (C₄H₉NH₃)₂PbCl₄ ( 1 ) is reported, adopting a 2D layered perovskite architecture, which exhibits an unprecedented coexistence of notable ferroelectricity and intrinsic white‐light emission. Decent above‐room‐temperature spontaneous polarization of ≈2.1 µC cm^?2 is confirmed for 1 . Particularly, it also exhibits brilliant broadband white‐light emission with a high color‐rendering‐index up to 86 under UV excitation. Structural analyses indicate that ferroelectricity of 1 originates from molecular reorientation of dynamic organic cations, as well as significant structural distortion of PbCl₆ octahedra that also contribute to its white‐light emission. This work paves an avenue to design new hybrid ferroelectrics for multifunctional application in the photoelectronic field.     

Polymer Field‐Effect Transistors Fabricated by the Sequential Gravure Printing of Polythiophene,Two Insulator Layers,and a Metal Ink Gate

The mass production technique of gravure contact printing is used to fabricate state‐of‐the art polymer field‐effect transistors (FETs). Using plastic substrates with prepatterned indium tin oxide source and drain contacts as required for display applications, four different layers are sequentially gravure‐printed: the semiconductor poly(3‐hexylthiophene‐2,5‐diyl) (P3HT), two insulator layers, and an Ag gate. A crosslinkable insulator and an Ag ink are developed which are both printable and highly robust. Printing in ambient and using this bottom‐contact/top‐gate geometry, an on/off ratio of >10⁴ and a mobility of 0.04 cm² V^?1 s^?1 are achieved. This rivals the best top‐gate polymer FETs fabricated with these materials. Printing using low concentration, low viscosity ink formulations, and different P3HT molecular weights is demonstrated. The printing speed of 40 m min^?1 on a flexible polymer substrate demonstrates that very high‐volume, reel‐to‐reel production of organic electronic devices is possible.     

Identification of Quaternary Shape Memory Alloys with Near‐Zero Thermal Hysteresis and Unprecedented Functional Stability

Improving the functional stability of shape memory alloys (SMAs), which undergo a reversible martensitic transformation, is critical for their applications and remains a central research theme driving advances in shape memory technology. By using a thin‐film composition‐spread technique and high‐throughput characterization methods, the lattice parameters of quaternary Ti–Ni–Cu–Pd SMAs and the thermal hysteresis are tailored. Novel alloys with near‐zero thermal hysteresis, as predicted by the geometric non‐linear theory of martensite, are identified. The thin‐film results are successfully transferred to bulk materials and near‐zero thermal hysteresis is observed for the phase transformation in bulk alloys using the temperature‐dependent alternating current potential drop method. A universal behavior of hysteresis versus the middle eigenvalue of the transformation stretch matrix is observed for different alloy systems. Furthermore, significantly improved functional stability, investigated by thermal cycling using differential scanning calorimetry, is found for the quaternary bulk alloy Ti_50.2Ni_34.4Cu_12.3Pd_3.1.