The impact of oxygen vacancy defect density on the nonlinearity and short-term plasticity of TiO₂-based exponential selector

The readout margin of the one selector-one RRAM crossbar array architecture is strongly dependent on the nonlinearity of the selector device. In this work, we demonstrated that the nonlinearity of Pt/TiO2/Pt exponential selectors increases with decreasing oxygen vacancy defect density. The defect density is controlled by modulating the sputtering pressure in the oxide deposition process. Our results reveal that the dominant conduction mechanisms of the Pt/TiO2/Pt structure transit from Schottky emission to Poole-Frenkel emission with the increase of sputtering pressure. Such transition is attributed to the rise of oxygen vacancy concentration. In addition, the short-term plasticity feature of the Pt/TiO2/Pt selector is shown to be enhanced with a lower defect density. These results suggest that low defect density is necessary for improved exponential selector performances.Agency for Science, Technology and Research (A*STAR)This work was supported by a RIE2020 ASTAR AME IAFICP Grant (No. I1801E0030)

Proton-assisted redox-based three-terminal memristor for synaptic device applications

Emerging technologies, i.e., spintronics, 2D materials, and memristive devices, have been widely investigated as the building block of neuromorphic computing systems. Three-terminal memristor (3TM) is specifically designed to mitigate the challenges encountered by its two-terminal counterpart as it can concurrently execute signal transmission and memory operations. In this work, we present a complementary metal-oxide-semiconductor-compatible 3TM with highly linear weight update characteristics and a dynamic range of ∼15. The switching mechanism is governed by the migration of oxygen ions and protons in and out of the channel under an external gate electric field. The involvement of the protonic defects in the electrochemical reactions is proposed based on the bipolar pulse trains required to initiate the oxidation process and the device electrical characteristics under different humidity levels. For the synaptic operation, an excellent endurance performance with over 256k synaptic weight updates was demonstrated while maintaining a stable dynamic range. Additionally, the synaptic performance of the 3TM is simulated and implemented into a four-layer neural network (NN) model, achieving an accuracy of ∼92% in MNIST handwritten digit recognition. With such desirable conductance modulation characteristics, our proposed 3T-memristor is a promising synaptic device candidate to realize the hardware implementation of the artificial NN.Agency for Science, Technology and Research (A*STAR)This work was supported by a RIE2020 ASTAR AME IAF-ICP grant (no. I1801E0030)

Ultrahigh quality microlasers from controlled self‐assembly of ultrathin colloidal semiconductor quantum wells

Colloidal quantum wells (CQWs) have emerged as a promising class of gain material in various optical feedback configurations. This is due to their unique excitonic features arising from their 1D quantum confinement. However, existing methods for integrating CQW onto microresonators will cause low laser quality due to uneven CQW coating. To overcome this, the use of liquid-interface kinetically driven self-assembly is proposed to coat ultrathin, close-packed layers of colloidal CdSe/Cd1−xZnxS core/shell CQWs between 7 and 14 nm onto the surface of silica microsphere cavities. The fabricated CQW-whispering-gallery-mode microlasers possess a commendable high quality (Q) factor of 13 000 at room temperature. Stable single-mode lasing output is demonstrated through evanescent field coupling between a CQW-coated microsphere and a thin uncoated microfiber in a 2D-3D microcavity configuration. These promising results highlight the suitability of the liquid-interface kinetically driven self-assembly method for realizing ultrathin CQW-coated microlasers and its high compatibility for integrating colloidal nanocrystals onto complex 3D microstructures for future miniaturized colloidal optoelectronic and photonic applications.Agency for Science, Technology and Research (A*STAR)Economic Development Board (EDB)Ministry of Education (MOE)National Research Foundation (NRF)Submitted/Accepted versionThis work was supportedby c and AME-IRG- A20E5c0083. The SEM imaging and EDS mapping wereperformed at the Facility for Analysis, Characterization, Testing and Sim-ulation (FACTS) at Nanyang Technological University, Singapore. H.V.D.and E.G.D. gratefully acknowledge the financial support in part from theSingapore Agency for Science, Technology and Research (A*STAR) MTCprogram under Grant No. M21J9b0085, Ministry of Education, Singapore,under its Academic Research Fund Tier 1 (MOE-RG62/20). H.V.D. alsogratefully acknowledges the support from TUBA. W.S.L. and C.X.X.L. ac-knowledge the support of EDB-IPP (REQ0165097)

Erratum to: Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition) (Autophagy, 12, 1, 1-222, 10.1080/15548627.2015.1100356

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Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field