Search

We report a thickness-dependent flexoresistance effect caused by strain gradient in SrTiO3 (STO) epitaxial thin films. The strain gradient in STO was induced by using an atomic force microscope diamond-coated tip. The depolarization field caused by the strain gradient changes the electrical state of the film, resulting in a decrease in the resistance of the films by 4–6 orders of magnitude. By testing the current–voltage (I–V) curves of STO films with different thicknesses, it is found that the flexoresistance behavior of STO films is obvious thickness dependent: the thicker the film, the higher the force threshold to trigger the film to enter a highly conductive state. The comparison of the surface morphology before and after the I–V test with loading shows that only when the thickness of the STO film is below 8 nm, the film can enter the conductive state from the insulating state without damaging the surface. During the electrical state switching process, the strain gradient caused by tip loading play an important role in the modification of the film barrier. [ABSTRACT FROM AUTHOR]

Ultrathin and transparent metal films are considered as desirable materials to substitute indium-tin oxide based transparent electrodes. In this work, we report that an Al-doped ZnO layer effectively induced the formation of epitaxial ultrathin and ultrasmooth Au films on mica. The ultrathin Au film shows optimum electrical conductivity, optical properties, and high tolerance to mechanical bending, including a low sheet resistance of 8 Ω/sq and a high average transmittance of 80.1%, and maintains low electric resistivity even after 1000 continuous bending cycles. Moreover, the Au/AZO anode-based organic light-emitting diode was fabricated with the maximum luminance intensity of 32 540 cd/cm2, which demonstrates that it is promising for application in next generation optoelectronic devices. [ABSTRACT FROM AUTHOR]

Freestanding perovskite thin films display many unprecedented properties and exhibit the potential to be easily integrated on other non-oxide substrates or layers. In this work, we demonstrated a pathway to synthesis freestanding perovskite oxide thin films by using brownmillerite SrCoO2.5 as a sacrificial layer. Four representative freestanding perovskite oxide films, e.g., ferromagnetic SrRuO3, La0.7Sr0.3MnO3, dielectric SrTiO3, and ferroelectric Pb(Zr0.2Ti0.8)O3, were produced by etching SrCoO2.5 in Fe(NO3)3 weak acidic solution at room temperature. A 80 nm SrRuO3, which served as an H+ conduction channel, was deposited as a bottom layer of SrCoO2.5 to trigger a quick dissolution for the exfoliation of SrTiO3 and Pb(Zr0.2Ti0.8)O3 poor H+ conductor. Their crystal structure and physical properties were well retained in transferred films. Our work demonstrated the wide applicability of SrCoO2.5 as a sacrificial layer on the synthesis of freestanding perovskite oxide thin films. [ABSTRACT FROM AUTHOR]

Large data storage at reduced dimension is of a great deal of interest in spintronic devices in which magnetic oxide films lead for realizing the modulation of perpendicular magnetic anisotropy (PMA). Herein, we report the modulation of PMA in oxide heterostructures composed of one manganite layer sandwiched between two cobaltite layers, i.e., LaCoO3−δ/La0.7Sr0.3MnO3/LaCoO3−δ via oxygen vacancies. The PMA is originated by the orbital reconstruction and ferromagnetic exchange interaction at the interface between the CoO6 and MnO6 octahedra layers. The modulation ratio up to a significant value ∼200% of PMA can be realized through the phase transition of LaCoO3−δ layers between perovskite and brownmillerite via deprivation or replenishment of oxygen sites. The antiferromagnetic superexchange interaction at the interface between the oxygen-deficient CoO4 tetrahedra layer and the adjacent MnO6 octahedral layer with lattice distortion may suppress the magnetization and PMA. This work ensures promising outcomes in situ modulation of PMA in oxide films such as ferroelectric polarization or ionic liquid gating via the transport of oxygen vacancies. [ABSTRACT FROM AUTHOR]

Exchange bias lies in the core of cutting-edge technologies, for instance, high-density data storage, spin valves, and high-frequency magnetic devices. As the devices with flexibility have become vital in the forefront of technology, the maintenance of exchange bias under high flexion is highly desired. This paper reports the strong exchange bias in flexible freestanding La0.7Sr0.3MnO3/BiFeO3 membranes with decent mechanical durability. The La0.7Sr0.3MnO3 layer is biased strongly by the BiFeO3 layer even in the freestanding state. At the same time, the strain is demonstrated to affect the strength of the exchange bias of the La0.7Sr0.3MnO3/BiFeO3 bilayer. Furthermore, the saturation magnetization and exchange bias field of the freestanding La0.7Sr0.3MnO3/BiFeO3 membranes are preserved well after 1000 bending cycles. Our work on freestanding membranes paves the way for manufacturing advanced flexible spintronic devices. [ABSTRACT FROM AUTHOR]

Recently, layered materials have been extensively studied and attracted unprecedented attention. Layered oxides with superior properties have potential applications for nanoscale devices. Here, we report variable supercells in layered bismuth manganite controlled by oxygen pressure and reveal the strong piezoelectric responses from the layered supercells with tunable physical properties, including an approximately three-times difference in the magnetization range and 10% difference in the optical transmittance. The tunability of the sublattice from Bi3O3 to Bi2O2 in supercells is realized by a precise oxygen pressure control of 10 mTorr and 100 mTorr, respectively. The results presented here show a tantalizing opportunity to discover emerging multifunctional oxides for future nanoelectronics. [ABSTRACT FROM AUTHOR]

In this paper, high-performance conducting Al-doped ZnO (AZO) electrodes were deposited on transparent and flexible muscovite mica substrates. The use of mica as a substrate material makes a van der Waals epitaxy possible, which significantly improves the structural, electrical, and optical properties of deposited AZO single-crystal-like films. AZO/mica retains its low electric resistivity, even after continuous bending of up to 1000 times on account of the unique layered structure of mica. When used as a transparent heater, AZO/mica shows an ultrahigh heating rate (200 °C/s) across large areas, which is a record among flexible transparent heaters. [ABSTRACT FROM AUTHOR]

5-nm thick Co4N layers capped with 3-nm thick Au layers were grown epitaxially on SrTiO3(001) substrates by molecular beam epitaxy using solid Co and a radio-frequency NH3 plasma. Spin and orbital magnetic moments of the Co4N layers were estimated using x-ray magnetic circular dichroism (XMCD) measurements at 300 K. The site-averaged Co 3d spin magnetic moment is evaluated to be about 1.4 μB, which is smaller than that predicted theoretically (1.58 μB). The element-specific XMCD intensities for the Co L3 edge and N K edge show that the magnetic moment is induced at the N atoms. [ABSTRACT FROM AUTHOR]