Dynamic mechanical control of local vacancies in NiO thin films.

The manipulation of local ionic behavior via external stimuli in oxide systems is of great interest because it can help in directly tuning material properties. Among external stimuli, mechanical force has attracted intriguing attention as novel stimulus for ionic modulation. Even though effectiveness of mechanical force on local ionic modulation has been validated in terms of static effect, its real-time i.

Enhancement of resistive switching under confined current path distribution enabled by insertion of atomically thin defective monolayer graphene.

Resistive random access memory (ReRAM) devices have been extensively investigated resulting in significant enhancement of switching properties. However fluctuations in switching parameters are still critical weak points which cause serious failures during 'reading' and 'writing' operations of ReRAM devices. It is believed that such fluctuations may be originated by random creation and rupture of conducting filaments inside ReRAM oxides.

A new simple method for point contact Andreev reflection (PCAR) using a self-aligned atomic filament in transition-metal oxides.

Point contact Andreev reflection (PCAR) has become a standard method for measuring the spin polarization (P) of spintronic materials due to its unique simplicity and the firm physical ground, but it is still challenging to achieve a clean point contact between a superconductor (SC) and a metal (N) for implementing PCAR. In this work, we suggest a much simpler method for PCAR measurement, where a point contact between SC and N is provided by a metallic filament in a transition-metal oxide generated by electrical bias. This method has been successfully demonstrated using a structure composed of Nb/NiO/Pt, where P of the Ni filament was estimated to be about 40%, consistent with the known value of the bulk Ni.

Controlled mechnical modification of manganite surface with nanoscale resolution.

We investigated the surfaces of magnetoresistive manganites, La(1-x)Ca(x)MnO3 and La(2-2x)Sr(1+2x)Mn2O7, using a combination of ultrahigh vacuum conductive, electrostatic and magnetic force microscopy methods. Scanning as-grown film with a metal tip, even with zero applied bias, was found to modify the surface electronic properties such that in subsequent scans, the conductivity is reduced below the noise level of conductive probe microscopy. Scanned areas also reveal a reduced contact potential difference relative to the pristine surface by ∼0.

Ultra-thin resistive switching oxide layers self-assembled by field-induced oxygen migration (FIOM) technique.

High-performance ultra-thin oxide layers are required for various next-generation electronic and optical devices. In particular, ultra-thin resistive switching (RS) oxide layers are expected to become fundamental building blocks of three-dimensional high-density non-volatile memory devices. Until now, special deposition techniques have been introduced for realization of high-quality ultra-thin oxide layers.

Mechanical control of electroresistive switching.

Hysteretic metal-insulator transitions (MIT) mediated by ionic dynamics or ferroic phase transitions underpin emergent applications for nonvolatile memories and logic devices. The vast majority of applications and studies have explored the MIT coupled to the electric field or temperarture. Here, we argue that MIT coupled to ionic dynamics should be controlled by mechanical stimuli, the behavior we refer to as the piezochemical effect.

Confining grains of textured Cu2O films to single-crystal nanowires and resultant change in resistive switching characteristics.

By confining columnar grains of textured oxide film using anodized aluminum oxide template, we could obtain a grain-boundary-free (GB-free) cuprous oxide (Cu(2)O) nanowire arrays with a narrow diameter distribution and a high density under the same electrochemical deposition condition. A two-terminal device fabricated using an individual GB-free nanowire and Au/Cr electrodes exhibits bipolar resistive switching contrary to the unipolar one of a textured film, and Schottky-like conduction. On the other hand, a nanowire device with Pt electrodes reveals non-switching behavior and Ohmic conduction.

Nanoscale lithography on monolayer graphene using hydrogenation and oxidation.

Monolayer graphene is one of the most interesting materials applicable to next-generation electronic devices due to its transport properties. However, realization of graphene devices requires suitable nanoscale lithography as well as a method to open a band gap in monolayer graphene. Nanoscale hydrogenation and oxidation are promising methods to open an energy band gap by modification of surface structures and to fabricate nanostructures such as graphene nanoribbons (GNRs).