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In this study, cobalt-doped hexagonal phase WO3 nanorods were prepared by a template-free hydrothermal method. The effects of varying the cobalt doping concentration on the microscopic morphology and electrochromic properties of hexagonal phase WO3 films were investigated. Films synthesized with the optimal cobalt element doping concentration demonstrate a notable improvement in their electrochromic properties compared to the pure hexagonal phase WO3 films. The film doped with 1.5% Co exhibited excellent cycling stability, retaining 98.55% of its original value after 500 cycles. The introduction of cobalt results in the formation of a nanorod structure with a high specific surface area within the film. This structure provides additional reaction sites for the electrochromic reaction process, thereby enhancing the optical modulation and coloration efficiency of WO3. The resulting films with excellent electrochromic properties provide a convenient and effective means for ion-doped modification of WO3-based electrochromic films. [ABSTRACT FROM AUTHOR]

To search for ways to improve the performance of selectors, crossbar-structured Au/Ag/HfOx(2 nm)/HfO2(4 nm)/Ag-NIs/Au devices with embedded Ag nanoislands (Ag-NIs) and dual hafnium oxide layers with different Hf:O ratios were prepared. Highly ordered Ag-NIs were prepared by electron beam evaporation with the help of an ultrathin anodic aluminum oxide (AAO) template. A 4-nm HfO2 layer was deposited by plasma-enhanced atomic layer deposition (PEALD) with tetrakis-ethyl methylaminohafnium (TEMAHf) as the precursor and O-plasma as the oxygen source (PEALD-HfO2), and a 2-nm HfOx (x = 1.60) layer was deposited by atomic layer deposition (ALD) with TEMAHf as the precursor and H2O as the oxygen source (ALD-HfOx). Au/Ag/HfOx(2 nm)/HfO2(4 nm)/Ag/Au, Au/Ag/HfOx(6 nm)/Ag-NIs/Au, and Au/Ag/HfO2(6 nm)/Ag-NIs/Au devices were also prepared for comparison. For the Au/Ag/HfOx/HfO2/Ag-NIs/Au device, the embedded Ag-NIs could effectively eliminate the need for an electroforming process, improve the volatile threshold switching (TS) endurance, and decrease the variation in the threshold voltages. The device could maintain volatile TS behavior under a high working current due to the dual-layer structure. By combining XPS characterization and measurements of the electrical properties of devices, we have proposed a phenomenological mechanism model that can be used to well explain the TS behavior of the Au/Ag/HfOx/HfO2/Ag-NIs/Au device. This work demonstrates that the introduction of Ag-NIs and a dual-layer structure is the effective way to improve the performance of selectors. [ABSTRACT FROM AUTHOR]

TiN/HfO2/ Ce O x /TiN memristors were prepared by magnetron sputtering. To further improve their performance, the devices were rapidly thermally annealed at different temperatures for different times. Compared with those of unannealed devices, the coefficients of variation (CVs) of the set voltage ( V SET ) and the reset voltage ( V RESET ) were reduced by 35.1% and 59.4%, respectively, and the CVs of the resistances in low and high resistance states ( R LRS and R HRS ) were reduced by 70.2% and 52.7%, respectively, after annealing at 400°C for 2 min in air. Through X-ray diffraction, X-ray photoelectron spectroscopy, and I ‐ V curves of the devices before and after annealing, we propose that the combined effect of grain growth (i.e., grain boundary reduction) and decreased oxygen vacancy content in the switching film resulting from annealing is responsible for the improvement in the switching parameter distribution of TiN/HfO2/ Ce O x /TiN devices. This work presents a simple way to enhance the performance of memristors. [ABSTRACT FROM AUTHOR]

There are unrevealed factors that bring about the performance variations of resistive switching devices. In this work, Pt/CeOx/Pt devices prepared by magnetron sputtering showed rectification in their asymmetrical current–voltage (I–V) curves during voltage sweeps. X-ray photoelectron spectroscopy showed that the deposited CeOx film had an inhomogeneous composition, and more oxygen vacancies existed in CeOx near the top electrode. The asymmetrical resistance change of the Pt/CeOx/Pt devices can be explained by the presence of more charged oxygen vacancies in CeOx near the top electrode, along with the Schottky conduction mechanism. This work reveals that the compositional inhomogeneity is inevitable in the magnetron sputtering of oxide targets like CeO2 and can be an important source of device-to-device and cycle-to-cycle variations of memristors. [ABSTRACT FROM AUTHOR]

Volatile threshold-switching (TS) devices have been used as selectors and to simulate neurons in neural networks. It is necessary to find new ways to improve their performance. The randomness of conductive filament (CF) growth and the endurance of the devices are urgent issues at present. Here, we explored embedded Ag nanoislands (NIs) in HfO2-based TS devices to limit the position of the CF and facilitate its growth at the same time. The Au/Ag(2 nm)/HfO2(4 nm)/Ag NIs/Au volatile TS devices exhibited forming-free characteristics with improved endurance compared with the devices without Ag NIs, which was ascribed to the enhanced localization of the electrical field and increased oxygen vacancies in HfO2 induced by the Ag NIs. A mechanism was proposed to explain the volatile TS behaviors of the devices. The Ag NIs and the thickness of the HfO2 layers played key roles in whether the devices required forming. This work shows that the use of metal NIs is an effective and convenient way to improve the performance of TS devices. [ABSTRACT FROM AUTHOR]

In this study, cobalt-doped hexagonal phase WO 3 nanorods were prepared by a template-free hydrothermal method. The effects of varying the cobalt doping concentration on the microscopic morphology and electrochromic properties of hexagonal phase WO 3 films were investigated. Films synthesized with the optimal cobalt element doping concentration demonstrate a notable improvement in their electrochromic properties compared to the pure hexagonal phase WO 3 films. The film doped with 1.5% Co exhibited excellent cycling stability, retaining 98.55% of its original value after 500 cycles. The introduction of cobalt results in the formation of a nanorod structure with a high specific surface area within the film. This structure provides additional reaction sites for the electrochromic reaction process, thereby enhancing the optical modulation and coloration efficiency of WO 3 . The resulting films with excellent electrochromic properties provide a convenient and effective means for ion-doped modification of WO 3 -based electrochromic films.