A two-terminal memristor memory based on a single VO2 nanowire is reported that can not only provide switchable resistances in a large range of about four orders of magnitude but can also maintain the resistances by a low bias voltage. The phase transition of the single VO2 nanowire was driven by the bias voltage of 0.34 V without using any heat source. The memristive behavior of the single VO2 nanowire was confirmed by observing the switching and non-volatile properties of resistances when voltage pulses and low bias voltage were applied, respectively. Furthermore, multiple retainable resistances in a large range of about four orders of magnitude can be utilized by controlling the number and the amount of voltage pulses under the low bias voltage. This is a key step towards the development of new low-power and two-terminal memory devices for next-generation non-volatile memories.

Methoxy‐functionalized triphenylamine‐imidazole derivatives that can simultaneously work as hole transport materials (HTMs) and interface‐modifiers are designed for high‐performance and stable perovskite solar cells (PSCs). Satisfying the fundamental electrical and optical properties as HTMs of p‐i‐n planar PSCs, their energy levels can be further tuned by the number of methoxy units for better alignment with those of perovskite, leading to efficient hole extraction. Moreover, when they are introduced between perovskite photoabsorber and low‐temperature solution‐processed NiO x interlayer, widely featured as an inorganic HTM but known to be vulnerable to interfacial defect generation and poor contact formation with perovskite, nitrogen and oxygen atoms in those organic molecules are found to work as Lewis bases that can passivate undercoordinated ion‐induced defects in the perovskite and NiO x layers inducing carrier recombination, and the improved interfaces are also beneficial to enhance the crystallinity of perovskite. The formation of Lewis adducts is directly observed by IR, Raman, and X‐ray photoelectron spectroscopy, and improved charge extraction and reduced recombination kinetics are confirmed by time‐resolved photoluminescence and transient photovoltage experiments. Moreover, UV‐blocking ability of the organic HTMs, the ameliorated interfacial property, and the improved crystallinity of perovskite significantly enhance the stability of PSCs under constant UV illumination in air without encapsulation.

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The surface composition and structure of SiC (hexagonal crystallites) are studied under Ar-ion bombardment, high-temperature cycling and adsorption of oxygen. Such treatments are necessary for surface cleaning and they also simulate environments in potential applications of SiC elements. Oxygen adsorption on surfaces which result after various cycles of Ar-ion bombardment and heating, i.e., with varying surface compositions, is studied to reveal details of the initial steps of oxidation. The experimental techniques were AES, XPS, and BAES (bremsstrahlung-induced AES). Bombardment with 3-keV Ar ions results in a nearly stoichiometric (1:1) surface. The implanted Ar accumulates strongly in the subsurface region during annealing at 900 °C. Annealing at higher temperatures (1200 °C) releases the Ar but also leads to decomposition of the surface, with the loss of Si. Oxygen adsorbs on the surface, in a reaction which mainly involves silicon atoms, and with an oxygen coverage related to the initial silicon surface concentration. At room temperature, the adsorption reaction contains two stages as for oxygen on clean silicon surfaces.