Ultrathin (sub-2 nm) Al2O3/MgO memristors were recently developed using an
The emergence of memristive behavior in amorphous–crystalline 2D oxide heterostructures, which are synthesized by atomic layer deposition (ALD) of a few‐nanometer amorphous Al2O3layers onto atomically thin single‐crystalline ZnO nanosheets, is demonstrated. The conduction mechanism is identified based on classic oxygen vacancy conductive channels. ZnO nanosheets provide a 2D host for oxygen vacancies, while the amorphous Al2O3facilitates the generation and stabilization of the oxygen vacancies. The conduction mechanism in the high‐resistance state follows Poole–Frenkel emission, and in the the low‐resistance state is fitted by the Mott–Gurney law. From the slope of the fitting curve, the mobility in the low‐resistance state is estimated to be ≈2400 cm2V−1s−1, which is the highest value reported in semiconductor oxides. When annealed at high temperature to eliminate oxygen vacancies, Al is doped into the ZnO nanosheet, and the memristive behavior disappears, further confirming the oxygen vacancies as being responsible for the memristive behavior. The 2D heterointerface offers opportunities for new design of high‐performance memristor devices.
more » « less- Award ID(s):
- 1720415
- NSF-PAR ID:
- 10457613
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 32
- Issue:
- 22
- ISSN:
- 0935-9648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract in vacuo atomic layer deposition (ALD) process that minimizes unintended defects and prevents undesirable leakage current. These memristors provide a unique platform that allows oxygen vacancies (VO) 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 VO-doping via modular MgO atomic layer insertion into an otherwise pristine insulating Al2O3atomic layer stack (ALS) using anin vacuo ALD. 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 VOconcentration and distribution. Understanding such a correlation is critical to an atomic-scale control of the switching behavior of ultrathin memristors. -
more » « less
Full utilization of the high storage capacity of conversion electrode materials as tin oxide (SnO2) in lithium‐ion batteries is hindered by the high volumetric expansion due to the high lithium storability which can lead to major cell damage and consequent safety issues. To overcome this issue, two promising approaches, nanostructures and buffer layers, are combined and evaluated. SnO2nanowires (NWs) are coated with an aluminum oxide (Al2O3) buffer layer to investigate the combination SnO2–Al2O3. Strong differences in the crystallinity after cycling between the SnO2/Al2O3core/shell NW‐based heterostructure and uncoated SnO2NWs based on detailed structural analysis are shown via transmission electron microscopy (TEM) and determination of the elemental distribution of tin, oxygen, lithium, and aluminum via energy‐dispersive X‐Ray spectroscopy and energy‐filtered TEM in the as‐prepared and postmortem nanostructures. The core/shell NWs exhibit two different states after charge/discharge cycling, amorphous or crystalline, depending on the NW diameter; for the uncoated SnO2NWs, only an amorphous postmortem structure is found. Additionally, differences in the elemental distribution for the amorphous and crystalline postmortem SnO2/Al2O3core/shell NWs, especially for tin, are measured. Consequently, the structures and effects of the Al2O3coating on the lithiation behavior of SnO2NW‐based heterostructures are discussed.
-
more » « less
Abstract Smart windows are energy‐efficient windows whose optical transparency can be switched between highly transparent and opaque states in response to incident solar illumination. Transparent and conductive metal nanomesh (NM) films are promising candidates for thermochromic smart windows due to their excellent thermal conductivity, high optical transparency at near infrared wavelengths, and outstanding stability. In this study, ZnO/Au/Al2O3NM films with periodicities of 200 and 370 nm are reported. The ZnO/Au/Al2O3NM film with a 370 nm periodicity exhibits a transmittance over 90% at 550 nm and sheet resistance lower than 20 Ω sq−1. Based on a standard figure of merit, this structure outperforms current state‐of‐the‐art NM films. Here, the integration of ZnO/Au/Al2O3NM films into a thermochromic perovskite smart window is also demonstrated. The transparency of the smart window structure is manipulated by transient resistive heating to trigger the thermochromic transition to the opaque state, which can be then maintained solely by 1‐sun, AM 1.5 G illumination. This climate‐adaptive, low power‐activated, and fast‐switching smart window structure opens new pathways toward its practical application in the real world.
-
more » « less
Abstract Cs2SnI6perovskite displays excellent air stability and a high absorption coefficient, promising for photovoltaic and optoelectronic applications. However, Cs2SnI6‐based device performance is still low as a result of lacking optimized synthesis approaches to obtain high quality Cs2SnI6crystals. Here, a new simple method to synthesize single crystalline Cs2SnI6perovskite at a liquid–liquid interface is reported. By controlling solvent conditions and Cs2SnI6supersaturation at the liquid–liquid interface, Cs2SnI6crystals can be obtained from 3D to 2D growth with controlled geometries such as octahedron, pyramid, hexagon, and triangular nanosheets. The formation mechanisms and kinetics of complex shapes/geometries of high quality Cs2SnI6crystals are investigated. Freestanding single crystalline 2D nanosheets can be fabricated as thin as 25 nm, and the lateral size can be controlled up to sub‐millimeter regime. Electronic property of the high quality Cs2SnI62D nanosheets is also characterized, featuring a n‐type conduction with a high carrier mobility of 35 cm2V−1s−1. The interfacial reaction‐controlled synthesis of high‐quality crystals and mechanistic understanding of the crystal growth allow to realize rational design of materials, and the manipulation of crystal growth can be beneficial to achieve desired properties for potential functional applications.
-
more » « less
Anatase TiO2is a promising anode material for lithium‐ion batteries (LIBs) owing to its low cost and stability. However, the intrinsically kinetic limits seriously hindered its lithium‐ion storage capability. Here we present that anatase TiO2with rich oxygen vacancies can enhance its lithium‐ion storage performance. We synthesize anatase TiO2with well‐retained hierarchical structure by annealing the H2Ti5O11·3H2O yolk‐shell spheres precursor in nitrogen atmosphere. EPR and XPS data evidence that the oxygen‐deficient environment could generate abundant oxygen vacancies in the as‐derived anatase TiO2, which leads to improved electron conductivity and reduced charge‐transfer resistance. The rich oxygen vacancies and high structural integrity of the hierarchical yolk‐shell spheres enable the as‐derived anatase TiO2yolk‐shell spheres with a high specific capacity of 280 mAh g−1at 100 mA g−1and 71% of capacity retention after 5000 cycles at 2 A g−1.
