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A ferroelectric tunnelling heterostructure is presented in which both the height and the width of the tunnelling barrier can be electrically modulated, leading to a greatly enhanced tunnelling electroresistance. In Pt/BaTiO3/Nb:SrTiO3 heterostructures, an ON/OFF conductance ratio that is about an order of magnitude greater than those reported in normal ferroelectric tunnelling junctions, is demonstrated at room temperature.
Coherent twin boundaries, which usually form during the growth, deformation or annealing of crystalline solids, are widely described as perfect interfaces. Experiments and simulations now show that as-grown coherent twin boundaries in nanotwinned copper consist of incoherent segments and partial dislocations, and significantly affect the material’s mechanical behaviour and deformation mechanisms.
A highly selective and efficient approach to covalently bond complementary DNA strands in solution and on surfaces on demand is shown. The approach involves the substitution of a pair of complementary bases by cinnamate-based crosslinks, which can be activated on exposure to ultraviolet light, and allows chemical patterning of flat and curved surfaces down to micrometre and potentially submicrometre resolutions.
Although high proton conductivity and chemical stability in yttrium-doped barium zirconate are of interest for intermediate-temperature solid-oxide fuel cells, there are remaining issues regarding its defect chemistry and macroscopic proton-transport mechanism. Proton transport in this compound is shown to be limited by proton–dopant association, and the presence of two types of proton environment above room temperature are observed, reflecting differences in proton–dopant configurations.
The conversion efficiency of heat to electricity in thermoelectric materials depends on both their thermopower and electrical conductivity. It is now reported that, unlike their inorganic counterparts, organic thermoelectric materials show an improvement in both these parameters when the volume of dopant elements is minimized; furthermore, a high conversion efficiency is achieved in PEDOT:PSS blends.
Photoelectrochemical water-splitting is a promising route for the renewable production of hydrogen, but trade-offs between photoelectrode stability and efficiency remain problematic. A metal–oxide–semiconductor photoelectrode architecture demonstrates stable and efficient water splitting using narrow-bandgap semiconductors. Substantial improvement in the performance of Si-based photocathodes is achieved by combining a high-quality SiO2 layer and bilayer metal catalysts.
A transparent organic field-effect transistor allows the stimulation and recording of the bioelectrical activity of primary neural cells. The cells grow, differentiate and function on the device, which then provides the electrical stimulation, and enables the recording of extracellular current and optical imaging of the modulation of neuronal membrane potential.
The conversion of a spin current into an electric signal is known as the inverse spin Hall effect, and is expected to enable the full potential of spintronic devices to be realized. Although the effect has been extensively studied in inorganic metals and semiconductors, it is now shown also to occur in a solution-processed organic polymer placed in proximity to a magnetic insulator.
Despite recent progress in the synthesis and characterization of molybdenum disulphide, little is yet known about its microstructure. Using refined chemical vapour deposition synthesis, high-quality crystals of monolayer molybdenum disulphide have now been grown. Single-crystal islands and polycrystals containing tilt and mirror twin grain boundaries are characterized, and the influence of the grain boundaries on the material properties of molybdenum disulphide is assessed.
The development of metallic glasses is hindered by the lack of mechanistic understanding of why some alloys crystallize quickly and thus are poorer at forming glasses than those that crystallize slowly. A molecular dynamics study of the growth rate of a planar crystal surface in model metallic glasses now shows that their glass-forming ability is determined by the structure of the crystal/liquid interface.
The ferroelectric properties of BiFeO3 have been the subject of extensive study. Using a range of experimental tools and numerical modelling, it is now shown that its ferroic properties can also be manipulated by strain effects, giving rise to a variety of magnonic phenomena.
Spillover of reactants from one active site to another is important in heterogeneous catalysis but is notoriously hard to detect or control, especially for hydrogen. The hydrogen spillover pathway on a Pd–Cu alloy can now be controlled by reversible adsorption of a spectator molecule. This effect observed during a surface catalysed reaction should prove useful for controlling uptake and release of hydrogen in a model storage system.
The dissipation of heat towards cooler regions of a thermodynamic system is a ubiquitous phenomenon. It is now shown that collective excitations known as spin waves can be used to control the flow of heat in a ferrimagnet consisting of Y3Fe5O12.
The silver chalcogenide semimetals are known for their appealing magnetoresistive properties. It is now shown that when copper silver selenide is doped with nickel, these properties are maintained, resulting in high electron mobilities and, in turn, a significant thermoelectric effect.
Analytical techniques reveal that spherical calcium phosphate particles are the first mineralized structures to be formed in the calcification process in cardiovascular tissues. Furthermore, the inner sections of calcified lesions in patients with various cardiovascular diseases are identified as highly crystalline, spherical hydroxyapatite particles that differ in structure from bone mineral.
The range of phenomena associated with the two-dimensional electron gas occurring at oxide interfaces has garnered significant attention. By performing a finite-size scaling analysis, the universality class of the magnetic field-driven quantum phase transition that occurs at the superconducting LaTiO3/SrTiO3 interface is now established.
Pseudocapacitance is commonly associated with surface or near-surface reversible redox reactions. The kinetics of charge storage in T-Nb2O5 electrodes is now quantified and the mechanism of lithium intercalation pseudocapacitance should prove to be important in obtaining high-rate charge-storage devices.
Nickel–cadmium and nickel–metal hydride batteries exhibit memory effects but lithium-ion batteries are widely believed to have none. Now, a memory effect for LiFePO4 positive electrodes that appears after only one cycle of partial charge and discharge is reported. This observation is important as the slight voltage change that it causes can lead to substantial erroneous estimation of the state of charge of batteries.
The variety of electronic processes occurring within an organic light-emitting diode (OLED) make the prediction of their emission characteristics problematic. It is now shown that all the relevant processes occurring in a stacked OLED can be modelled down to the molecular scale, in turn leading to accurate emission profiles.
Designing synthetic surfaces whose properties dynamically adapt in response to mechanical stimuli is challenging. Now, liquid-infused nanoporous elastic substrates that respond to stretching by continuously changing their transparency and wettability—a consequence of smooth variations in surface roughening as the liquid flows inside the pores—are demonstrated.
