Strong Magnetic Anisotropy of Epitaxial PrVO Thin Films on SrTiO Substrates with Different Orientations.

We have probed the structural and magnetic properties of PrVO (PVO) thin films grown on the (001)-, (110)-, and (111)-oriented SrTiO (STO) substrates. By changing the substrate orientation, the film out-of-plane orientation can be tuned to [110], [100]/[010], and [011]/[311], with different in-plane crystallographic variants. Accommodation of these variants on the different substrates implies different strain states, which have direct influence on the magnetic properties of PVO films.

Complementary Resistive Switching and Synaptic-Like Memory Behavior in an Epitaxial SrFeO Thin Film through Oriented Oxygen-Vacancy Channels.

Oxygen-vacancy-ordered brownmillerite oxides offer a reversible topotactic phase transition by significantly varying the oxygen stoichiometry of the material without losing its lattice framework. This phase transition leads to substantial changes in the physical and chemical properties of brownmillerite oxides, including electrical and ion conductivity, magnetic state, and oxygen diffusivity. In this study, the variations in the resistive switching mode of the epitaxial brownmillerite SrFeO thin film in the device were studied by systematically controlling the oxygen concentration, which could be varied by changing the compliance current during the first electroforming step.

Effects of the Heterointerface on the Growth Characteristics of a Brownmillerite SrFeO Thin Film Grown on SrRuO and SrTiO Perovskites.

Manipulation of the heterointerfacial structure and/or chemistry of transition metal oxides is of great interest for the development of novel properties. However, few studies have focused on heterointerfacial effects on the growth characteristics of oxide thin films, although such interfacial engineering is crucial to determine the growth dynamics and physical properties of oxide heterostructures. Herein, we show that heterointerfacial effects play key roles in determining the growth process of oxide thin films by overcoming the simple epitaxial strain energy.

Topotactic Phase Transition Driving Memristive Behavior.

Redox-based memristive devices are one of the most attractive candidates for future nonvolatile memory applications and neuromorphic circuits, and their performance is determined by redox processes and the corresponding oxygen-ion dynamics. In this regard, brownmillerite SrFeO has been recently introduced as a novel material platform due to its exceptional oxygen-ion transport properties for resistive-switching memory devices. However, the underlying redox processes that give rise to resistive switching remain poorly understood.

Confining vertical conducting filament for reliable resistive switching by using a Au-probe tip as the top electrode for epitaxial brownmillerite oxide memristive device.

We had discovered novel resistance switching phenomena in SrCoO epitaxial thin films. We have interpreted the results in terms of the topotactic phase transformation between their insulating brownmillerite phase and the conducting perovskite phase and the existence of a rather vertical conducting filament due to its inherent layered structure. However, the rough interface observed between the SrCoO and the Au top electrode (area ~10000 μm) was assumed to result in the observed fluctuation in key switching parameters.

Brownmillerite thin films as fast ion conductors for ultimate-performance resistance switching memory.

An oxide-based resistance memory is a leading candidate to replace Si-based flash memory as it meets the emerging specifications for future memory devices. The non-uniformity in the key switching parameters and low endurance in conventional resistance memory devices are preventing its practical application. Here, a novel strategy to overcome the aforementioned challenges has been unveiled by tuning the growth direction of epitaxial brownmillerite SrFeO thin films along the SrTiO [111] direction so that the oxygen vacancy channels can connect both the top and bottom electrodes rather directly.

Magnetoresistance Versus Oxygen Deficiency in Epi-stabilized SrRu Fe O Thin Films.

Oxygen vacancies have a profound effect on the magnetic, electronic, and transport properties of transition metal oxide materials. Here, we studied the influence of oxygen vacancies on the magnetoresistance (MR) properties of SrRu Fe O epitaxial thin films (x = 0.10, 0.

Magnetic and electric properties of stoichiometric BiMnO3 thin films.

It has been suggested that BiMnO3 is a material exhibiting both ferromagnetism and ferroelectricity. Stoichiometry is rather easily achieved in a polycrystalline sample, and ferromagnetic properties have been well documented for bulk samples. Stoichiometry in thin films has been difficult to obtain, and many physical properties have exhibit wide distributions mainly due to the stoichiometry problem.

Ferromagnetism and Ru-Ru distance in SrRuO3 thin film grown on SrTiO3 (111) substrate.

Epitaxial SrRuO3 thin films were grown on both (100) and (111) SrTiO3 substrates with atomically flat surfaces that are required to grow high-quality films of materials under debate. The following notable differences were observed in the (111)-oriented SrRuO3 films: (1) slightly different growth mode, (2) approximately 10 K higher ferromagnetic transition temperature, and (3) better conducting behavior with higher relative resistivity ratio, than (100)c-oriented SrRuO3 films. Together with the reported results on SrRuO3 thin films grown on (110) SrTiO3 substrate, the different physical properties were discussed newly in terms of the Ru-Ru nearest neighbor distance instead of the famous tolerance factor.

Brush-shaped ZnO heteronanorods synthesized using thermal-assisted pulsed laser deposition.

Brush-shaped ZnO heteronanostructures were synthesized using a newly designed thermal-assisted pulsed laser deposition (T-PLD) system that combines the advantages of pulsed laser deposition (PLD) and a hot furnace system. Branched ZnO nanostructures were successfully grown onto CVD-grown backbone nanowires by T-PLD. Although ZnO growth at 300 °C resulted in core-shell structures, brush-shaped hierarchical nanostructures were formed at 500-600 °C.