Scintillators are widely utilized for radiation detections in many fields, such as nondestructive inspection, medical imaging, and space exploration. Lead halide perovskite scintillators have ...recently received extensive research attention owing to their tunable emission wavelength, low detection limit, and ease of fabrication. However, the low light yields toward X‐ray irradiation and the lead toxicity of these perovskites severely restricts their practical application. A novel lead‐free halide is presented, namely Rb2CuBr3, as a scintillator with exceptionally high light yield. Rb2CuBr3 exhibits a 1D crystal structure and enjoys strong carrier confinement and near‐unity photoluminescence quantum yield (98.6%) in violet emission. The high photoluminescence quantum yield combined with negligible self‐absorption from self‐trapped exciton emission and strong X‐ray absorption capability enables a record high light yield of ≈91056 photons per MeV among perovskite and relative scintillators. Overall, Rb2CuBr3 provides nontoxicity, high radioluminescence intensity, and good stability, thus laying good foundations for potential application in low‐dose radiography.
A new lead‐free halide Rb2CuBr3 scintillator with 1D crystal structure is presented. It exhibits self‐trapped exciton emission with a large Stokes shift (0.91 eV). Thus, it has near‐unity photoluminescence quantum yield (98.6%) and a high radioluminescence light yield of ≈91 056 photons per MeV.
An X‐ray detector with high sensitivity would be able to increase the generated signal and reduce the dose rate; thus, this type of detector is beneficial for applications such as medical imaging and ...product inspection. The inorganic lead halide perovskite CsPbBr3 possesses relatively larger density and a higher atomic number in contrast to its hybrid counterpart. Therefore, it is expected to provide high detection sensitivity for X‐rays; however, it has rarely been studied as a direct X‐ray detector. Here, a hot‐pressing method is employed to fabricate thick quasi‐monocrystalline CsPbBr3 films, and a record sensitivity of 55 684 µC Gyair−1 cm−2 is achieved, surpassing all other X‐ray detectors (direct and indirect). The hot‐pressing method is simple and produces thick quasi‐monocrystalline CsPbBr3 films with uniform orientations. The high crystalline quality of the CsPbBr3 films and the formation of self‐formed shallow bromide vacancy defects during the high‐temperature process result in a large µτ product and, therefore, a high photoconductivity gain factor and high detection sensitivity. The detectors also exhibit relatively fast response speed, negligible baseline drift, and good stability, making a CsPbBr3 X‐ray detector extremely competitive for high‐contrast X‐ray detections.
The hot‐pressing fabrication method for quasi‐monocrystalline CsPbBr3 thick film and the performance of their X‐ray detection are introduced. The high crystalline quality of CsPbBr3 films and the formation of self‐formed shallow bromide vacancy defects during the high‐temperature process result in a large µτ product and therefore high photoconductivity gain factor and record‐high detection sensitivity.
Abstract
Ion transport and hydrodynamic flow through nanometer-sized channels (nanopores) have been increasingly studied owing to not only the fundamental interest in the abundance of novel phenomena ...that has been observed but also their promising application in innovative nanodevices, including next-generation sequencers, nanopower generators, and memristive synapses. We first review various kinds of materials and the associated state-of-the-art processes developed for fabricating nanoscale pores, including the emerging structures of DNA origami and 2-dimensional nanopores. Then, the unique transport phenomena are examined wherein the surface properties of wall materials play predominant roles in inducing intriguing characteristics, such as ion selectivity and reverse electrodialysis. Finally, we highlight recent progress in the potential application of nanopores, ranging from their use in biosensors to nanopore-based artificial synapses.
Abstract
X-ray detectors are broadly utilized in medical imaging and product inspection. Halide perovskites recently demonstrate excellent performance for direct X-ray detection. However, ionic ...migration causes large noise and baseline drift, limiting the detection and imaging performance. Here we largely eliminate the ionic migration in cesium silver bismuth bromide (Cs
2
AgBiBr
6
) polycrystalline wafers by introducing bismuth oxybromide (BiOBr) as heteroepitaxial passivation layers. Good lattice match between BiOBr and Cs
2
AgBiBr
6
enables complete defect passivation and suppressed ionic migration. The detector hence achieves outstanding balanced performance with a signal drifting one order of magnitude lower than all previous studies, low noise (1/
f
noise free), a high sensitivity of 250 µC Gy
air
−1
cm
–2
, and a spatial resolution of 4.9 lp mm
−1
. The wafer area could be easily scaled up by the isostatic-pressing method, together with the heteroepitaxial passivation, strengthens the competitiveness of Cs
2
AgBiBr
6
-based X-ray detectors as next-generation X-ray imaging flat panels.
The development of in‐memory computing has opened up possibilities to build next‐generation non‐von‐Neumann computing architecture. Implementation of logic functions within the memristors can ...significantly improve the energy efficiency and alleviate the bandwidth congestion issue. In this work, the demonstration of arithmetic logic unit functions is presented in a memristive crossbar with implemented non‐volatile Boolean logic and arithmetic computing. For logic implementation, a standard operating voltage mode is proposed for executing reconfigurable stateful IMP, destructive OR, NOR, and non‐destructive OR logic on both the word and bit lines. No additional voltages are needed beyond “VP” and its negative component. With these basic logic functions, other Boolean functions are constructed within five devices in at most five steps. For arithmetic computing, the fundamental functions including an n‐bit full adder with high parallelism as well as efficient increment, decrement, and shift operations are demonstrated. Other arithmetic blocks, such as subtraction, multiplication, and division are further designed. This work provides solid evidence that memristors can be used as the building block for in‐memory computing, targeting various low‐power edge computing applications.
In‐memory computation tasks of a memristive arithmetic logic unit are demonstrated based on stateful logic in a memristive crossbar. Highly reconfigurable and parallel operations are designed with simplified instructions, including Boolean logic, addition, subtraction, multiplication, division, increment, decrement, and shift operations. The energy efficiency and short latency prove its advance for future in‐memory computing applications.
Through oxygen profile engineering, we fabricated W/AlOx/Al2O3/Pt bilayer memristors with a 250-nm feature size. The AlOx fabricated by sputtering serves as an oxygen vacancy source, whereas the ...Al2O3 deposited by atomic layer deposition acts as a dominant resistive switching (RS) layer. Our devices show forming-free RS behaviors with high speed (28 ns), uniform resistance distribution, large on/off ratio (~103@100K, ~103@298K, and ~80@400K), and good retention. Besides, temperature stability with record high endurance from cryogenic to high-temperature (108@100K, 1010@298K, and 107@400K) is demonstrated, to the best of our knowledge.
The synaptic weight modification depends not only on interval of the pre‐/postspike pairs according to spike‐timing dependent plasticity (classical pair‐STDP), but also on the timing of the preceding ...spike (triplet‐STDP). Triplet‐STDP reflects the unavoidable interaction of spike pairs in natural spike trains through the short‐term suppression effect of preceding spikes. Second‐order memristors with one state variable possessing short‐term dynamics work in a way similar to the biological system. In this work, the suppression triplet‐STDP learning rule is faithfully demonstrated by experiments and simulations using second‐order memristors. Furthermore, a leaky‐integrate‐and‐fire (LIF) neuron is simulated using a circuit constructed with second‐order memristors. Taking the advantage of the LIF neuron, various neuromimetic dynamic processes, including local graded potential leaking out, postsynaptic impulse generation and backpropagation, and synaptic weight modification according to the suppression triplet‐STDP rule, are realized. The realized weight‐dependent pair‐ and triplet‐STDP rules are clearly in line with findings in biology. The physically realized triplet‐STDP rule is powerful in developing direction and speed selectivity for complex pattern recognition and tracking tasks. These scalable artificial synapses and neurons realized in second‐order memristors can intrinsically capture the neuromimetic dynamic processes; they are the promising building blocks for constructing brain‐inspired computation systems.
Compared with the classical pair‐spike‐timing dependent plasticity (STDP), the triplet‐STDP is an advanced synaptic plasticity that induces improved learning capability. The triplet‐STDP is physically demonstrated and a leaky‐integrate‐and‐fire (LIF) neuron is simulated using second‐order memristors. The biorealistic implementation of the triplet‐STDP and the LIF neuron offers an efficient approach to the artificial intelligence through a simple artificial neural network.
In this article, we quantify several nonideal characteristics of memristor synaptic devices, such as the limited conductance states, write nonlinearities, and variations, and comprehensively ...investigate their effects on the convolutional neural network (CNN) performance. Our result shows that the available conductance states (N state ), asymmetric write nonlinearities, and cycle-to-cycle (C2C) variation are critical factors to the learning accuracy, while symmetric write nonlinearities and device-to-device variation go trivial. We accordingly propose three strategies to mitigate their impacts on CNN performance: 1) limiting the weight range to improve the utilization of Nstate; 2) adopting a new "with-read" update scheme to mitigate the effects of asymmetric write nonlinearities; and 3) employing multiple memristors for each kernel element to alleviate the impact of C2C variation. Our work would provide guidance for the hardware implementation and optimization of CNN in memristor crossbar.
Costly data movement in terms of time and energy in traditional von Neumann systems is exacerbated by emerging information technologies related to artificial intelligence. In‐memory computing (IMC) ...architecture aims to address this problem. Although the IMC hardware prototype represented by a memristor is developed rapidly and performs well, the sneak path issue is a critical and unavoidable challenge prevalent in large‐scale and high‐density crossbar arrays, particularly in three‐dimensional (3D) integration. As a perfect solution to the sneak‐path issue, a self‐rectifying memristor (SRM) is proposed for 3D integration because of its superior integration density. To date, SRMs have performed well in terms of power consumption (aJ level) and scalability (>102 Mbit). Moreover, SRM‐configured 3D integration is considered an ideal hardware platform for 3D IMC. This review focuses on the progress in SRMs and their applications in 3D memory, IMC, neuromorphic computing, and hardware security. The advantages, disadvantages, and optimization strategies of SRMs in diverse application scenarios are illustrated. Challenges posed by physical mechanisms, fabrication processes, and peripheral circuits, as well as potential solutions at the device and system levels, are also discussed.
This review summarizes the research progress in self‐rectifying memristors (SRM) and SRM‐based applications including 3D memory, in‐memory computing, neuromorphic computing, and hardware security. Through a comprehensive analysis of the advantages and disadvantages of SRMs in different application scenarios, as well as challenges at the device, 3D integration, and peripheral circuit levels, corresponding research ideas and potential solutions are proposed.
In-memory computing architecture is an emerging revolutionary computing paradigm that can break the von Neumann bottleneck. Computing methodology and circuit codesign using the CMOS compatible 1T1R ...resistive random access memory (RRAM) integration structure is presented in this paper. Functionally complete Boolean logic and arithmetic functions are experimentally demonstrated. With a single 40-nm CMOS process 1T1R unit, each of the 16 binary logics can be realized in two logic steps with an additional readout step for cascading, which shows functional reconfiguration and low computational complexity. Up to 10 7 cycles of NAND and XOR logic operations are performed to validate the correctness and reliability. Moreover, several fundamental adder circuits are designed and experimentally demonstrated in 1T1R devices as the proof of concept of the 1T1R computing architecture. The adders proposed in this paper include a ripple-carry adder and its optimized design and a carry-select adder, which all show promising advantages in nonvolatility, computation speed, and circuit area. This paper reports the most complex yet efficient RRAM-based 8-bit addition function experimentally so far and lays a solid foundation for constructing the future in-memory computing architecture.
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