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Abstract Ultrathin (sub-2 nm) Al₂O₃/MgO memristors were recently developed using anin vacuoatomic layer deposition (ALD) process that minimizes unintended defects and prevents undesirable leakage current. These memristors provide a unique platform that allows oxygen vacancies (V_O) to be inserted into the memristor with atomic precision and study how this affects the formation and rupture of conductive filaments (CFs) during memristive switching. Herein, we present a systematic study on three sets of ultrathin Al₂O₃/MgO memristors with V_O-doping via modular MgO atomic layer insertion into an otherwise pristine insulating Al₂O₃atomic layer stack (ALS) using anin vacuoALD. At a fixed memristor thickness of 17 Al₂O₃/MgO atomic layers (∼1.9 nm), the properties of the memristors were found to be affected by the number and stacking pattern of the MgO atomic layers in the Al₂O₃/MgO ALS. Importantly, the trend of reduced low-state resistance and the increasing appearance of multi-step switches with an increasing number of MgO atomic layers suggests a direct correlation between the dimension and dynamic evolution of the conducting filaments and the V_Oconcentration and distribution. Understanding such a correlation is critical to an atomic-scale control of the switching behavior of ultrathin memristors. 

As metal/insulator/metal tunnel junctions (MIMTJs), such as magnetic tunnel junctions and Josephson tunnel junctions, push the insulating tunnel barrier (TB) towards the ultrathin regime (<1 nm) defects inherent in current physical vapor deposition methods become a fundamental obstacle to create pinhole-free and defect-free MIMTJs. Atomic layer deposition (ALD) could offer a solution by providing a conformal, leak-free tunnel barrier with low defect density and atomic thickness as demonstrated recently in ALD Al2O3 tunnel barriers. A question arises on the viability of the ALD TBs in practical circuits of multilayer structures on which increased roughness may occur. To answer this question, this work investigates electron tunneling properties of ALD Al2O3 tunnel barriers of 1.1 –1.2 Å in thickness on half-cell MIMTJs of Al/Fe/Nb fabricated on multilayer structures of different surface roughness using in situ scanning tunneling spectroscopy. Remarkably, the tunnel barriers grown on the raised multilayer device analogue only show a moderate decrease in barrier height from 1.63 eV, to 1.51 eV and to 1.27 eV as the surface roughness increases from 0.9 nm to 2.3 nm, and to 15 nm, alongside a slight decrease in ALD coverage from ∼96%, to ∼93% and 84% on these samples. Overall, these results validate the ALD TBs of atomic thickness for future 3D arrays of devices. 

Abstract Localized surface plasmon resonance (LSPR) is shown to be effective in trapping light for enhanced light absorption and hence performance in photonic and optoelectronic devices. Implementation of LSPR in all‐inorganic perovskite nanocrystals (PNCs) is particularly important considering their unique advantages in optoelectronics. Motivated by this, the first success in colloidal synthesis of AuCu/CsPbCl₃core/shell PNCs and observation of enhanced light absorption by the perovskite CsPbCl₃shell of thickness in the range of 2–4 nm, enabled by the LSPR AuCu core of an average diameter of 7.1 nm, is reported. This enhanced light absorption leads to a remarkably enhanced photoresponse in PNCs/graphene nanohybrid photodetectors using the AuCu/CsPbCl₃core/shell PNCs, by more than 30 times as compared to the counterparts with CsPbCl₃PNCs only (8–12 nm in dimension). This result illustrates the feasibility in implementation of LSPR light trapping directly in core/shell PNCs for high‐performance optoelectronics.