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We have investigated microscale to nanoscale ferroelectric domain and surface engineering of a near-stoichiometric LiNbO[SUB3] crystal by using scanning force microscopy. The single crystals LiNbO[SUB3] fixed on metal substrates were polished to a 5 μm thickness. Artificial patterns of inverted-domain structures were fabricated in the samples, where polarization directions of the domains were switched by scanning the samples with a conductive cantilever while applying voltages. Furthermore, the negatively polarized surfaces in the patterns were preferentially etched in HF solution. As a result, cavity and mound-shaped surfaces were fabricated; these structures could be used to create functional templates and devices. [ABSTRACT FROM AUTHOR]

An all-solid-state electric-double-layer transistor (EDLT) with a Gd-doped CeO2 (GDC) oxide ion conductor/SrTiO3 (STO) insulator structure has been developed. At 473 K, the drain current of the EDLT was well controlled, from less than nA order to μA order, by electrostatic carrier doping at the GDC/STO interface due to oxide ion (O2-) migration in the GDC, in contrast to an inactiveness at room temperature. The EDL capacitance at the interface, measured with an ac impedance spectroscopy, was 14 μF cm-2, higher than that reported for a microporous-SiO2 EDLT and comparable to that of an ionic-liquid-gated EDLT. [ABSTRACT FROM AUTHOR]

Bipolar resistance switching (BRS) behavior and the effects of atmosphere (air, vacuum, O2 gas, or N2 gas) on BRS behavior occurred in the top and bottom interfaces in the M(top electrode)/WO3-x/Pt(bottom electrode) (M = Pt, Au) devices were investigated. Stable BRS only can be obtained in the interface with Pt electrode. And, the top Pt/WO3-x interface exhibited stable BRS only in an oxygen-rich atmosphere (air and O2 gas). In contrast, the bottom WO3-x/Pt interface showed stable BRS under any atmosphere. Based on the x-ray photoelectron spectroscopy measurement on Pt, Au/WO3-x interfaces, it is identified that the oxygen migration process during resistance switching mainly occurs between the Pt/WO3-x interface and Pt electrode. [ABSTRACT FROM AUTHOR]

Atomic switch, operating by forming and dissolving a metal-protrusion in a nanogap, shows an exponentially large bias dependence and a faster switching with increasing temperature and decreasing off-resistance. These major characteristics are explained with a simple model where the electrochemical potential at the subsurface of solid-electrolyte electrode determines the precipitation rate of metal atoms and the electric-field in the nanogap strongly affects the formation of metal-protrusion. Theoretically calculated switching time, based on this model, well reproduced the measured properties of a Cu2S-based atomic switch as a function of bias, temperature and off-resistance, providing a significant physical insight into the mechanism. [ABSTRACT FROM AUTHOR]

The structures of inverted nanodomains in LiNbO3 crystals were investigated using atomic force microscopy (AFM) combined with piezoresponse force microscopy and atomic force acoustic microscopy. The acoustic and AFM topographic images reflected in domain structures with polarization orientation revealed that unexpected antiparallel domains randomly exist in inverted nanodomains in congruent LiNbO3 but not in near-stoichiometric one. The Gibbs free energy change ΔG associating with the internal field Eint in congruent LiNbO3 was discussed. We propose that nonstoichiometric defects, which caused Eint during polarization reversal, play a key role in formation of antiparallel domains in congruent LiNbO3 crystals. [ABSTRACT FROM AUTHOR]

Metallic nanoparticle deposition from an aqueous solution onto the +Z surfaces of LiNbO3 nanodomain patterns has been demonstrated. The distribution of the selectively deposited Ag particles was uniform and their sizes were 2–10 nm both in the diameter and height. The authors have inferred the mechanism by which the photovoltaic effect causes Ag particles to be deposited selectively on the +Z surfaces. The photovoltaic current density and the ferroelectric crystal thickness are found to be fundamental parameters of the photocatalytic deposition. [ABSTRACT FROM AUTHOR]

The stability of domains engineered in near-stoichiometric and congruent composition LiTaO3 crystals was investigated after heat treatment using scanning force microscopy. Piezoresponse images of the domains showed that the heat treatment had induced backswitching in the near-stoichiometric crystals and that the degree of backswitching depended on the domain structure and heating temperature. No backswitching was observed in the congruent composition crystals after the same heat treatment. The thermal stability of engineered LiTaO3 domains thus depends on the number of nonstoichiometric defects, the domain wall energy, and the pyroelectric effect. [ABSTRACT FROM AUTHOR]

The surface potential imaging of nanoscale domains engineered on near-stoichiometric LiNbO3 (SLN) crystals was investigated using Kelvin probe-based, electrostatic force microscopy. The surface potential image reflected in the domain structure was clearly obtained using heat treatment in vacuum due to the decreases in spontaneous polarization and screening charge adsorption. In-vacuum observation revealed that the surface potential contrast and polarity of nanoscale engineered domains can be repeatedly changed by switching the temperature between 298 and 393 K, demonstrating the controllability of the spontaneous polarization distribution in SLN crystals. [ABSTRACT FROM AUTHOR]

The authors examined the electronic transport of a solid electrolyte resistive switch. Using element analysis and the temperature dependence of its electronic transport, they deduced that the conductive path is composed of Cu metal precipitated in the solid electrolyte film by an electrochemical reaction. Furthermore, they observed Coulomb blockade phenomena at 4 K when the switch was in the off state. Their observations and experimental results suggest that the metallic conductive path consists of metallic islands separated by tunneling barriers and that switching between the on and off states originates from modulation in the tunneling barriers. [ABSTRACT FROM AUTHOR]

Nanosized inverted domain dots in ferroelectric materials have potential applications in ultrahigh-density rewritable data storage systems. Here, a data storage system based on scanning nonlinear dielectric microscopy and thin films of ferroelectric single-crystal lithium tantalite is presented. Through domain engineering, nanosized inverted domain dots have been successfully formed at a data density of 1.50 Tbit/in.². Nanosized inverted domain dots in ferroelectric materials have potential applications in ultrahigh-density rewritable data storage systems. Here, a data storage system based on scanning nonlinear dielectric microscopy and thin films of ferroelectric single-crystal lithium tantalite is presented. Through domain engineering, nanosized inverted domain dots have been successfully formed at a data density of 1.50 Tbit/in.². [ABSTRACT FROM AUTHOR]

Epitaxial Ca1-xSrxVO3 (0 ≦ x ≦ 1) thin films were grown on (100)-oriented SrTiO3 substrates by using the pulsed laser deposition technique. In contrast to the previous report that metal-insulator transition (MIT) in Ca1-xSrxVO3 (CSVO) was achieved only for extremely thin films (several nm thick), MIT was observed at 39, 72, and 113 K for films with a thickness of 50 nm. The electronic structure was investigated by hard and soft X-ray photoemission spectroscopy (HX-PES and SX-PES). The difference between these PES results was significant due to the variation in an escape depth of photoelectrons of PES. While HX-PES showed that the V 2p3/2 spectra consisted of four peaks (V5+, V4+, V3+, and V2+/1+), SX-PES showed only three peaks (V5+, V4+, and V3+). This difference can be caused by a strain from the substrate, which leads to the chemical disorder (V5+, V4+, V3+, and V2+/1+). The thin film near the substrate is affected by the strain. The positive magnetoresistance is attributed to the effect of electron-electron interactions in the disorder system. Therefore, the emergence of MIT can be explained by the electron-electron interactions from the chemical disorder due to the strain. [ABSTRACT FROM AUTHOR]