The ever‐increasing demand for higher‐capacity digital memory shows no sign of declining. The conventional strategy for meeting such demand, i.e. shrinking of the memory cell size, will no longer be ...useful at some point in the future, owing to economic reasons and performance degradation. Nevertheless, performance of computing systems will keep improving for the next generation information technology. This indicates the necessity to consider a fundamentally disparate approach to enhance memory technology. Here, the current status of computer memory chips is reviewed and the pros and cons of the present technology are discussed from computing system, fabrication technology, and materials points of view. Based on this knowledge, the limitations of the present technologies are described, and the possible solutions suggested up to now are reassessed. Finally, a shift in the fundamental computational paradigm from von Neumann computing to other alternatives such as neuromorphic computing and material implication, is commented upon.
Perpectives on semiconductor memory devices are reviewed from the point of view of memory systems to materials. Fundamental innovations in computing systems, materials, and fabrication technologies for the ever‐increasing density and performance of memory are necessary to support improvements in IT. A fundamental shift in the paradigm from von Neumann computing to neuromorphic computing or something else, such as material implications, can be conceived.
Highly transparent and nanostructured nickel oxide (NiO) films through pulsed laser deposition are introduced for efficient CH3NH3PbI3 perovskite solar cells. The (111)‐oriented nanostructured NiO ...film plays a key role in extracting holes and preventing electron leakage as hole transporting material. The champion device exhibits a power conversion efficiency of 17.3% with a very high fill factor of 0.813.
A thrombus (blood clot), composed mainly of activated platelets and fibrin, obstructs arteries or veins, leading to various life-threatening diseases. Inspired by the distinctive physicochemical ...characteristics of thrombi such as abundant fibrin and an elevated level of hydrogen peroxide (H2O2), we developed thrombus-specific theranostic (T-FBM) nanoparticles that could provide H2O2-triggered photoacoustic signal amplification and serve as an antithrombotic nanomedicine. T-FBM nanoparticles were designed to target fibrin-rich thrombi and be activated by H2O2 to generate CO2 bubbles to amplify the photoacoustic signal. In the phantom studies, T-FBM nanoparticles showed significant amplification of ultrasound/photoacoustic signals in a H2O2-triggered manner. T-FBM nanoparticles also exerted H2O2-activatable antioxidant, anti-inflammatory, and antiplatelet activities on endothelial cells. In mouse models of carotid arterial injury, T-FBM nanoparticles significantly enhanced the photoacoustic contrast specifically in thrombosed vessels and significantly suppressed thrombus formation. We anticipate that T-FBM nanoparticles hold great translational potential as nanotheranostics for H2O2-associated cardiovascular diseases.
A nociceptor is a critical and special receptor of a sensory neuron that is able to detect noxious stimulus and provide a rapid warning to the central nervous system to start the motor response in ...the human body and humanoid robotics. It differs from other common sensory receptors with its key features and functions, including the "no adaptation" and "sensitization" phenomena. In this study, we propose and experimentally demonstrate an artificial nociceptor based on a diffusive memristor with critical dynamics for the first time. Using this artificial nociceptor, we further built an artificial sensory alarm system to experimentally demonstrate the feasibility and simplicity of integrating such novel artificial nociceptor devices in artificial intelligence systems, such as humanoid robots.
The recent progress in ferroelectricity and antiferroelectricity in HfO2‐based thin films is reported. Most ferroelectric thin film research focuses on perovskite structure materials, such as ...Pb(Zr,Ti)O3, BaTiO3, and SrBi2Ta2O9, which are considered to be feasible candidate materials for non‐volatile semiconductor memory devices. However, these conventional ferroelectrics suffer from various problems including poor Si‐compatibility, environmental issues related to Pb, large physical thickness, low resistance to hydrogen, and small bandgap. In 2011, ferroelectricity in Si‐doped HfO2 thin films was first reported. Various dopants, such as Si, Zr, Al, Y, Gd, Sr, and La can induce ferroelectricity or antiferroelectricity in thin HfO2 films. They have large remanent polarization of up to 45 μC cm−2, and their coercive field (≈1–2 MV cm−1) is larger than conventional ferroelectric films by approximately one order of magnitude. Furthermore, they can be extremely thin (<10 nm) and have a large bandgap (>5 eV). These differences are believed to overcome the barriers of conventional ferroelectrics in memory applications, including ferroelectric field‐effect‐transistors and three‐dimensional capacitors. Moreover, the coupling of electric and thermal properties of the antiferroelectric thin films is expected to be useful for various applications, including energy harvesting/storage, solid‐state‐cooling, and infrared sensors.
Recent progress in ferroelectricity and antiferroelectricity in HfO2‐based thin films is comprehensively reviewed. The properties of ferroelectric HfO2‐based films, different from those of conventional ferroelectrics, are believed to solve the problems of conventional ferroelectrics in non‐volatile memory. Moreover, the pyroelectricity of antiferroelectric films is expected to be useful for various applications, including energy harvesting and storage, solid‐state cooling, and infrared sensors.
The promising energy storage properties of new lead‐free antiferroelectric HfxZr1‐xO2 (x = 0.1–0.4) films with high energy storage density are reported. The energy storage density of the Hf0.3Zr0.7O2 ...capacitor does not decrease with the increase in temperature up to 175 °C, and it decreases by only ≈4.5% after field cycling 109 times.
Vertically integrated NAND (V-NAND) flash memory is the main data storage in modern handheld electronic devices, widening its share even in the data centers where installation and operation costs are ...critical. While the conventional scaling rule has been applied down to the design rule of ≈15 nm (year 2013), the current method of increasing device density is stacking up layers. Currently, 176-layer-stacked V-NAND flash memory is available on the market. Nonetheless, increasing the layers invokes several challenges, such as film stress management and deep contact hole etching. Also, there should be an upper bound for the attainable stacking layers (400-500) due to the total allowable chip thickness, which will be reached within 6-7 years. This review summarizes the current status and critical challenges of charge-trap-based flash memory devices, with a focus on the material (floating-gate vs charge-trap-layer), array-level circuit architecture (NOR vs NAND), physical integration structure (2D vs 3D), and cell-level programming technique (single vs multiple levels). Current efforts to improve fabrication processes and device performances using new materials are also introduced. The review suggests directions for future storage devices based on the ionic mechanism, which may overcome the inherent problems of flash memory devices.
PDF
