Resistive switching memory, which is mostly based on polycrystalline thin films, suffers from wide distributions in switching parameters-including set voltage, reset voltage, and resistance-in their low- and high-resistance states. One of the most commonly used methods to overcome this limitation is to introduce inhomogeneity. By contrast, in this paper, we obtained uniform resistive switching parameters and sufficiently low forming voltage by maximizing the uniformity of an epitaxial thin film. To achieve this result, we deposited an SrFeOx/SrRuO3 heteroepitaxial structure onto an SrTiO3 (001) substrate by pulsed laser deposition, and then we deposited an Au top electrode by electron-beam evaporation. This device exhibited excellent bipolar resistance switching characteristics, including a high on/off ratio, narrow distribution of key switching parameters, and long data retention time. We interpret these phenomena in terms of a local, reversible phase transformation in the SrFeOx film between brownmillerite and perovskite structures. Using the brownmillerite structure and atomically uniform thickness of the heteroepitaxial SrFeOx thin film, we overcame two major hurdles in the development of resistive random-access memory devices: high forming voltage and broad distributions of switching parameters.

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The electrochemical reduction of carbon dioxide (CO ) to value-added products is a promising approach to reducing excess CO in the atmosphere. However, the development of electrocatalysts for highly selective and efficient electrochemical CO reduction has been challenging because protons are usually easier to reduce than CO in an aqueous electrolyte. Recently, single-atom catalysts (SACs) have been suggested as candidate CO reduction catalysts due to their unique catalytic properties. To prepare single-atom metal active sites, the stabilization of metal atoms over conductive supports such as graphene sheets to prevent metal aggregation is crucial. To address this issue, a facile method was developed to prepare single-atom nickel active sites on reduced graphene oxide (RGO) sheets for the selective production of carbon monoxide (CO) from CO . The tris(2-benzimidazolylmethyl)amine (NTB) ligand was introduced as a linker that can homogeneously disperse nickel atoms on the graphene oxide (GO) sheets. Because the NTB ligands form strong interactions with the GO sheets by π-π interactions and with nickel ions by ligation, they can effectively stabilize nickel ions on GO sheets by forming Ni(NTB)-GO complexes. High-temperature annealing of Ni(NTB)-GO under inert atmosphere produces nickel- and nitrogen-doped reduced graphene oxide sheets (Ni-N-RGO) with single-atom Ni-N active sites. Ni-N-RGO shows high CO reduction selectivity in the reduction of CO to CO with 97 % faradaic efficiency at -0.8 V vs. RHE (reversible hydrogen electrode).

Microdonut-shaped GaN/Inx Ga1-x N light-emitting diode (LED) microarrays are fabricated for variable-color emitters. The figure shows clearly donut-shaped light emission from all the individual microdonut LEDs. Furthermore, microdonut LEDs exhibit spatially-resolved blue and green EL colors, which can be tuned by either controlling the external bias voltage or changing the size of the microdonut LED.

Human serum albumin (HSA) is the most abundant plasma protein. The main reason for using HSA as a versatile tool for drug delivery is based on its ability to accumulate in tumors. However, the mechanism of albumin accumulation in tumors is not yet clear. Many researchers using HSA as a drug-carrier have focused on the passive tumor targeting by enhanced permeability and retention (EPR) effect, while other investigators proposed that albumin binding proteins mediate albumin accumulation in tumors. We investigated whether HSA accumulation in tumors is mediated by the EPR effect or by secreted protein acidic and rich in cysteine (SPARC), which is known to be an albumin-binding protein.Methods: To investigate the role of SPARC on HSA accumulation in tumors, we compared HSA uptake in U87MG glioblastoma cells with different SPARC expression. U87MG cells generally express high levels of SPARC and were, therefore, used as SPARC-rich cells. SPARC-less U87MG (U87MG-shSPARC) cells were established by viral-shSPARC transduction. We detected cellular uptake of fluorescence-labeled HSA by confocal microscopy in U87MG and U87MG-shSPARC cells. To demonstrate the mechanism of HSA accumulation in tumors, we injected FNR648-labeled HSA and FITC-labeled dextran in U87MG and U87MG-shSPARC tumor-bearing mice and observed their micro-distribution in tumor tissues.Results: HSA was internalized in cells by binding with SPARC in vitro. HSA accumulation in U87MG glioma was associated with SPARC expression in vivo. FITC-dextran was distributed in U87MG tumors in the vicinity of blood vessels. The distribution of HSA, on the other hand, was observed in the regions remote from blood vessels of U87MG tumor tissues but not in U87MG-shSPARC tumor tissues.Conclusion: Our results demonstrate that the tumor-distribution of HSA is affected not only by the EPR-effect but also by SPARC expression. SPARC enhances HSA accumulation in U87MG glioma and mediates active targeting of HSA in tumors.

An oxide-based resistance memory is a leading candidate to replace Si-based flash memory as it meets the emerging specifications for future memory devices. The non-uniformity in the key switching parameters and low endurance in conventional resistance memory devices are preventing its practical application. Here, a novel strategy to overcome the aforementioned challenges has been unveiled by tuning the growth direction of epitaxial brownmillerite SrFeO thin films along the SrTiO [111] direction so that the oxygen vacancy channels can connect both the top and bottom electrodes rather directly. The controlled oxygen vacancy channels help reduce the randomness of the conducting filament (CF). The resulting device displayed high endurance over 10 cycles, and a short switching time of ∼10 ns. In addition, the device showed very high uniformity in the key switching parameters for device-to-device and within a device. This work demonstrates a feasible example for improving the nanoscale device performance by controlling the atomic structure of a functional oxide layer.

We report the growth and transfer of centimeter-sized, epitaxial hexagonal boron nitride (h-BN) few-layer films using Ni(111) single-crystal substrates. The h-BN films were heteroepitaxially grown on 10 × 10 mm 2 or 20 × 20 mm 2 Ni(111) substrates using atmospheric pressure chemical vapor deposition with a single ammonia-borane precursor. The grown films were transferred to arbitrary substrates via an electrochemical delamination technique, and the remaining Ni(111) substrates were repeatedly re-used. A careful analysis of the growth parameters revealed that the crystallinity and area coverage of the h-BN films were mostly sensitive to the sublimation temperature of the ammonia-borane source. Moreover, various physical characterizations confirmed that the grown films exhibited the typical characteristics of hexagonal boron nitride layers over the entire area. Furthermore, the heteroepitaxial relationship between h-BN and Ni(111) and the overall crystallinity of the film were thoroughly investigated using a synchrotron radiation X-ray diffraction analysis including θ-2θ scans, grazing incident diffraction, and reciprocal space mapping. The crystallinity at the microscopic scale was further investigated using transmission electron microscopy (TEM)-based techniques, including selective area electron diffraction pattern mapping, electron back-scattered diffraction, and high-resolution TEM.

A novel characterization technique using both in situ reflection high-energy electron diffraction (RHEED) transmission mode and transmission electron microscopy (TEM) has been developed to investigate the growth behaviour of semiconductor nanostructures. RHEED employed in transmission mode enables the acquisition of structural information during the growth of nanostructures such as nanorods. Such real-time observation allows the investigation of growth mechanisms of various nanomaterials that is not possible with conventional ex situ analytical methods. Additionally, real-time monitoring by RHEED transmission mode offers a complete range of information when coupled with TEM, providing structural and chemical information with excellent spatial resolution, leading to a better understanding of the growth behaviour of nanomaterials. Here, as a representative study using the combined technique, the nucleation and crystallization of InAs nanorods and the epitaxial growth of InxGa1−xAs(GaAs) shell layers on InAs nanorods are explored. The structural changes in the InAs nanorods at the early growth stage caused by the transition of the local growth conditions and the strain relaxation processes that occur during epitaxial coating of the shell layers are shown. This technique advances our understanding of the growth behaviour of various nanomaterials, which allows the realization of nanostructures with novel properties and their application in future electronics and optoelectronics.