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In this work, we demonstrated a bottom-up growth of Ag@SiO2/Ag core-shell nanosphere arrays with tunable SiO2 interior insulator and the optimized surface-enhanced Raman scattering (SERS) substrate based on a nanostructure performed with both high sensitivity and large-area uniformity. Their morphological, structural, and optical properties were characterized, and the induced SERS activities were investigated theoretically by the FDTD simulation and experimentally using analyte molecules. An ultrathin SiO2 shell with tunable thickness can be synthesized pinhole-free by a chemical vapor deposition, working as an interior insulator between the Ag core and Ag out-layer coating. A detection limit as low as 10−12 M and an enhancement factor up to 3 × 107 were obtained, and the SERS signal was highly reproducible with small standard deviation. The method opened up a way to create a new class of SERS activity sensor with high-density 'hot spots', and it may play an important role in device design and the corresponding biological and food safety monitoring applications. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We investigate the resistive switching and ferroelectric polarization properties of high-quality epitaxial BiFeO3 thin films in various temperature ranges. The room temperature current–voltage (I–V) curve exhibits a well-established polarization-modulated memristor behavior. At low temperatures (< 253 K), the I–V curve shows an open circuit voltage (OCV), which possibly originates from the dielectric relaxation effects, accompanied with a current hump due to the polarization reversal displacement current. While at relative higher temperatures (> 253 K), the I–V behaviors are governed by both space-charge-limited conduction (SCLC) and Ohmic behavior. The polarization reversal is able to trigger the conduction switching from Ohmic to SCLC behavior, leading to the observed ferroelectric resistive switching. At a temperature of > 298 K, there occurs a new resistive switching hysteresis at high bias voltages, which may be related to defect-mediated effects. [ABSTRACT FROM AUTHOR]

A three-terminal device based on electronic phase separated manganites is suggested to produce high performance resistive switching. Our Monte Carlo simulations reveal that the conductive filaments can be formed/annihilated by reshaping the ferromagnetic metal phase domains with two cross-oriented switching voltages. Besides, by controlling the high resistance state (HRS) to a stable state that just after the filament is ruptured, the resistive switching remains stable and reversible, while the switching voltage and the switching time can be greatly reduced. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of the Cu-doped ZnO (ZnO:Cu) under c-axis pressure were studied using first-principle calculations. It was found that the ZnO:Cu undergoes a structural transition from Wurtzite to Graphite-like structure at a c-axis pressure of 7–8 GPa. This is accompanied by an apparent loss of ferromagnetic stability, indicating a magnetic transformation from a ferromagnetic state to a paramagnetic-like state. Further studies revealed that the magnetic instability is closely related to the variation in crystalline field originated from the structural transition, which is in association with the overlapping of spin–charge density between the Cu2+ and adjacent O2-. [ABSTRACT FROM AUTHOR]