We present a transparent and flexible optoelectronic material composed of vertically aligned ZnO NWs grown on reduced graphene/PDMS substrates. Large-area reduced graphene films were prepared on PDMS substrates by chemical exfoliation from natural graphite via oxidative aqueous dispersion and subsequent thermal reduction. ZnO NWs were hydrothermally grown on the reduced graphene film substrate and maintained their structural uniformity even in highly deformed states. The electrical contact between semiconducting ZnO NWs and the metallic graphene film was straightforwardly measured by electric force microscopy (EFM). It shows a typical metal-semiconductor ohmic contact without a contact barrier. Owing to the mechanical flexibility, transparency, and low contact barrier, the ZnO NWs/graphene hybrids show excellent field emission properties. Low turn-on field values of 2.0 V mm À1 , 2.4 V mm À1 , and 2.8 V mm À1 were measured for convex, flat, and concave deformations, respectively. Such variation of field emission properties were attributed to the modification of ZnO NWs emitter density upon mechanical deformation.

We report an efficient and environmentally benign biomimetic mineralization of TiO(2) at the graphitic carbon surface, which successfully created an ideal TiO(2)/carbon hybrid structure without any harsh surface treatment or interfacial adhesive layer. The N-doped sites at carbon nanotubes (CNTs) successfully nucleated the high-yield biomimetic deposition of a uniformly thick TiO(2) nanoshell in neutral pH aqueous media at ambient pressure and temperature and generated N-doped CNT (NCNT)/TiO(2) core/shell nanowires. Unlike previously known organic biomineralization templates, such as proteins or peptides, the electroconductive and high-temperature-stable NCNT backbone enabled high-temperature thermal treatment and corresponding crystal structure transformation of TiO(2) nanoshells into the anatase or rutile phase for optimized material properties. The direct contact of the NCNT surface and TiO(2) nanoshell without any adhesive interlayer introduced a new carbon energy level in the TiO(2) band gap and thereby effectively lowered the band gap energy. Consequently, the created core/shell nanowires showed a greatly enhanced visible light photocatalysis. Other interesting synergistic properties such as stimuli-responsive wettabilites were also demonstrated.

We report on the synthesis of one-dimensional (1D) Li 4 Ti 5 O 12 nanofibers through electrospinning and their outstanding electrochemical performances. Li 4 Ti 5 O 12 with a spinel structure is a promising candidate anode material for lithium rechargeable batteries due to its well-known zerostrain merits. In order to improve the electronic properties of spinel Li 4 Ti 5 O 12 , which are intrinsically poor, we processed the material into a nanofiber type of architecture to shorten the Li + and electron transport distance using a versatile electrospinning approach. The electrospun Li 4 Ti 5 O 12 nanofiber showed significantly enhanced discharging/charging properties, even at high rates that exceeded 10 C, demonstrating that the nanofiber offers an attractive architecture for enhanced kinetics.

Here we introduce angle-resolved piezoresponse force microscopy ͑AR-PFM͒, whereby the sample is rotated by 30°increments around the surface normal vector and the in-plane PFM phase signals are collected at each angle. We obtained the AR-PFM images of BaTiO 3 single crystal and cube-on-cube epitaxial ͑001͒ BiFeO 3 ͑BFO͒ thin film on SrRuO 3 / SrTiO 3 substrate, and confirmed that the AR-PFM provides more unambiguous information on the in-plane polarization directions than the conventional PFM method. Moreover, we found eight additional in-plane polarization variants in epitaxial BFO thin films, which are formed to mitigate highly unstable charged domain boundaries.

Using Kelvin force microscopy, the authors have investigated the potential distribution on ferroelectric films. The local distribution of potential was observed on downward, prepoled areas. The polarity of the potential corresponds to the screen charge. It was found that the electrical properties of the grain boundary affect the potential distribution. Most of the grain boundaries show a lower potential than the area inside the grain. The authors identified certain regions at the grain boundary with a very low potential. Such potential pits may act as efficient screen charge draining paths and may lead to important perturbations on the device level.

We report the dependence of the ferroelectric domain configuration and switching behavior on the shape ͑square versus round͒ of epitaxial BiFeO 3 ͑BFO͒ nanostructures. We fabricated ͑001͒ oriented BFO͑120 nm͒ / SrRuO 3 ͑SRO, 125 nm͒ film layers on ͑001͒ SrTiO 3 single crystals by rf magnetron sputter deposition, and patterned them to square ͑500ϫ 500 nm 2 ͒ and round ͑502 nm in diameter͒ shaped nanostructures by focused ion-beam lithography. The surface morphology and the crystalline structure of the nanostructures were characterized by scanning electron microscopy and x-ray diffraction, respectively, while the domain configuration was investigated using piezoelectric force microscopy. We found that the square-shaped nanostructures exhibit a single variant domain configuration aligned along the ͓111͔ direction, whereas the round-shaped nanostructures exhibit seven variants of domain configuration along the ͓111͔, ͓111͔, ͓111͔, ͓111͔, ͓111͔, ͓111͔, and ͓111͔ directions. Moreover, local d 33 piezoelectric coefficient measurements showed hysteresis loops with a strong displacement in the voltage axis ͑strong imprint͒ for the square-shaped nanostructures, while the round-shaped ones exhibited more symmetric loops. These findings have critical implications for the development of nanocapacitors for gigabyte to terabyte nonvolatile ferroelectric memories.

We have studied the effect of local surface potential distribution on its relaxation in the polycrystalline ferroelectric thin films. A lower surface potential region, i.e., potential pit, is generated near a grain boundary. The deep potential pit has a faster relaxation than the area far away from the potential pit due to the acceleration of the screen charge draining near the grain boundary and the domains formed by applying higher voltage have a faster relaxation due to the larger gradient of screen charge distribution. In addition, the surface potential and its relaxation depend on the sign of applying voltage. The result shows that the surface potential distribution may influence significantly to the reliability of bit signal on the memory devices.

A facile route is presented for the fabrication of spherical PbTiO3 (PTO) nanodot arrays on platinized silicon substrates using PbO vapor phase reaction sputtering on micellar monolayer films of polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) loaded with TiO2 sol–gel precursor. Short exposure to PbO transforms the amorphous TiO2 into polycrystalline PTO, while keeping the inherent size and periodicity of TiO2 nanodots. HRTEM images show that the spherical PTO nanodots, with an average size and height of 63 nm and 40 nm, respectively, are fixed on the Pt supported by residual carbon. XPS narrow scan spectra of Ti 2p and O 1s strongly verify the evolution of chemical identity and the reduction of the Ti‐O binding energy from TiO2 to PTO. The amplitude and phase images of piezoelectric force microscopy (PFM) confirm a multidomain structure attributed by the crystalline orientation of the PTO nanodots. Furthermore, the discrete PTO nanodots show remarkable switching properties due to the low strain field induced by the small lateral size, and the absence of domain pinning effects by grain boundary.