A MXene-GaN-MXene based multiple quantum well photodetector was prepared on patterned sapphire substrate by facile drop casting. The use of MXene electrodes improves the responsivity and reduces dark current, compared with traditional Metal-Semiconductor-Metal (MSM) photodetectors using Cr/Au electrodes. Dark current of the device using MXene-GaN van der Waals junctions is reduced by three orders of magnitude and its noise spectral intensity shows distinct improvement compared with the traditional Cr/Au–GaN–Cr/Au MSM photodetector. The improved device performance is attributed to low-defect MXene-GaN van der Waals interfaces. Thanks to the high quality MXene-GaN interfaces, it is possible to verify that the patterned substrate can locally improve both light extraction and photocurrent collection. The measured responsivity and specific detectivity reach as high as 64.6 A/W and 1.93 × 1012 Jones, respectively, making it a potential candidate for underwater optical detection and communication. The simple fabrication of MXene-GaN-MXene photodetectors spearheaded the way to high performance photodetection by combining the advantages of emerging 2D MXene materials with the conventional III-V materials.

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The recently demonstrated Cs3Bi2I9 single crystals (SCs) exhibit superior performance for X‐ray detection. More importantly, they do not contain any toxic lead element. However, compared with lead‐halide perovskites, one challenge for the Cs3Bi2I9 SC for X‐ray detection application is that it is difficult to prepare large‐sized and high‐quality SCs. Here, a liquid diffused separation induced crystallization (LDSC) method is employed to grow Cs3Bi2I9 SCs for eliminating the temperature fluctuation and convection currents caused by the thermal gradient in the growth solution. The resultant Cs3Bi2I9 SC exhibits a microstrain of 1.21 × 10–3, a resistivity of 1.12 × 109 Ω cm, a carrier mobility of 4.57 cm2 V–1 s–1, and a mobility‐lifetime product of 1.87 × 10–3 cm2 V–1. As a result, an X‐ray detector based on the high‐quality Cs3Bi2I9 SC exhibits an excellent dose rate linearity, a sensitivity of 964 µC Gyair–1 cm–2, and a limit of detection (LoD) of 44.6 nGyair s–1.

Abstract-Robotic swarms are distributed systems whose members interact via local control laws to achieve different behaviors. Practical missions may require a combination of different swarm behaviors, where these behavioral combinations are not known a priori but could arise dynamically due to changes in mission goals. Therefore, human interaction with the swarm (HIS) is needed. In this paper, we introduce, formally define and characterize a novel concept, Neglect Benevolence, that captures the idea that it may be beneficial for system performance if the human operator, after giving a command, waits for some time before giving a subsequent command to the swarm. This raises the important question of the existence and means of calculation of the optimal time for the operator to give input to the swarm in order to optimize swarm behavior. Human operators are limited in their ability to estimate the best time to give input to the swarm. Therefore, automated aids that calculate the optimal input time could help the human operator achieve the best system performance. Our contributions are as follows. First, we formally define the new notion of Neglect Benevolence. Second, we prove the existence of Neglect Benevolence for a class of linear dynamical systems. Third, we provide an analytic characterization and an algorithm for calculating the optimal input time. Fourth, we apply the analysis to the human control of swarm configuration.