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The generation and manipulation of single photons is important for quantum information and metrology. Highly bright and stable single-photon sources are now identified in silicon carbide, a wide-bandgap semiconductor widely used for photonic and electronic devices.
The LaAlO3/SrTiO3 interface plays host to a diverse range of physical phenomena. By imaging the electrostatic landscape with a specially designed detector it is shown that tetragonal domains give rise to a large extrinsic piezoelectricity.
The electrochemical reduction of oxygen to hydrogen peroxide requires selective and stable electrocatalysts. It is now shown that Pt–Hg nanoparticles display an order of magnitude improvement in the mass activity for hydrogen peroxide production compared with the best performing catalyst.
The propagation of light in photonic crystals with a honeycomb structure mirrors the behaviour of charges in graphene, therefore allowing for the investigation of electronic properties that cannot otherwise be accessed in graphene itself. This approach is now used to predict unexpected edge states that localize in the bearded edges of hexagonal lattices.
Oxide ion conductors are technologically relevant for applications in electrochemical devices such as sensors, separation membranes and fuel cells. Magnesium doping in Na0.5Bi0.5TiO3—a piezoelectric material that suffers from high leakage conductivity—now results in a family of ionic conductors that could prove significant not only for dielectric-based applications but also for intermediate-temperature solid-oxide fuel cells.
Proteins from bone extracellular matrix are known to mediate the organization of apatite crystals in bone. Now, electron microscopy, X-ray scattering and nuclear magnetic resonance measurements of the structure and organization of apatite nanoparticles and intact bone samples show that water also plays a significant role in orienting the apatite crystals, and that such structuring is mediated by a disordered mineral layer that coats the crystalline core of bone apatite.
Size effects and geometry can significantly modify the properties of nanoparticles with direct impact on their biocompatibility and chemical reactivity. Using high-resolution electron microscopy it is now shown that strain gradients induced in the oxide shell of cuboid Fe nanoparticles can lead to oxide domain formation and shape evolution of the particles.
Compared with their rigid counterparts, thin-film solar cells grown on flexible substrates usually display lower power-conversion efficiencies. Now, the application of a post-deposition alkaline treatment that modifies the chemical composition of the surfaces of Cu(In,Ga)Se2 thin films reduces optical losses in these flexible photovoltaic architectures. Furthermore, efficiencies comparable to solar cells based on polycrystalline silicon are achieved.
Metal fluorides/oxides are promising electrodes for lithium-ion batteries, but the mechanism by which they exhibit additional reversible capacity is still not well understood. By using high-resolution solid-state NMR techniques it is shown that extra capacity in this RuO2 system is due to the generation of LiOH and its subsequent reversible reaction with Li to form Li2O and LiH.
Traps in organic semiconducting crystals are healed when a perfluoropolyether oil is deposited on the surface of these materials, thus making possible the detection of intrinsic features of charge-carrier transport in rubrene and tetracene.
In organic semiconductors, disorder-induced traps can alter the mobility of the charges and introduce noise in transport measurements. It is now shown that simple drop-casting of perfluoropolyether on top of organic single-crystals is an effective strategy for healing charge traps. This method allows the intrinsic transport properties of these materials to be recovered as well as suppressing noise in Hall effect measurements.
Rare-earth hexagonal manganites are known for their multiferroic properties. Using parameters calculated from first principles, a theoretical description of the topological defects arising in these systems is now presented.
