Research articles

Multiferroics are promising for their ability to use an electric polarization to control magnetism and vice versa. However, ferroelastic effects during the switching of multiferroics such as BiFeO₃ destabilize the ferroelectric state. A new approach for the switching of these sorts of compound may now represent a solution to this problem.

Despite having many similarities with graphene, single-layer boron nitride has a very large bandgap. Now, single-layer hybrids consisting of a blend of domains of boron nitride and graphene have been synthesized. By varying the percentage of boron nitride it is possible to tune the electronic properties, which is a very promising development for potential devices.

In comparison with the plastic deformation of regular crystalline materials, the mechanisms that govern complex solids with hundreds of atoms in a single unit cell are much less understood. An unusual defect mechanism in complex solids suggests the coordinated movement of hundreds of atoms, a result that improves the understanding of the deformation mechanisms in these types of material.

While superconductivity experts investigate the fundamental properties of iron pnictides, it is worth wondering whether the properties of these materials are good enough for applications. A strategy for growing high-quality BaFe₂As₂ thin films shows that the use of an appropriate buffer layer allows very high critical currents to be reached.

Efforts in predicting crystal structures from first principles have mainly focused on the bulk materials. A general approach based on a genetic algorithm is now proposed to simulate grain boundaries and heterophase interfaces in multicomponent systems. The efficiency of the approach is demonstrated in the case of grain boundaries in SrTiO₃.

As a liquid approaches its glass transition its dynamics slow down and simultaneously the material becomes more heterogeneous. A static structural heterogeneity, now shown to be widely present in glass-forming liquids, is suggested to be the origin of this dynamic heterogeneity that links structural parameters to the glass transition.

The ability to exert control over domains in multiferroic materials is important in terms of the potential use of these materials. In the multiferroic YMnO₃, structural considerations lead to an unusual cloverleaf pattern of ferroelectric domains, where the domain walls are electrically insulating.

Resolving the surface structure and chemistry of oxides such as strontium titanate has so far proved difficult. Rings of six or eight corner-sharing TiO₄ tetrahedra and a homologous series of surface reconstructions for SrTiO₃(110) are now predicted.

The use of silicon nanostructures in solar cells offers a number of benefits, such as the fact they can be used on flexible substrates. A silicon wire-array structure, containing reflecting nanoparticles for enhanced absorption, is now shown to achieve 96% peak absorption efficiency, capturing 85% of light with only 1% of the silicon used in comparable commercial cells.

The origin of the effect that a magnetic field has on various electronic properties of organic semiconductors is still controversial. It is now shown that substituting hydrogen for deuterium in conducting polymers changes the response to a magnetic field substantially, proving the essential part played by hyperfine interaction in this effect.

The mechanical properties of many materials are different on the nanoscale than they are in the bulk. In the case of metallic glasses, nanometre-scale samples show enhanced ductility. This tensile ductility has now been quantified for samples with diameters down to 100 nm, where a new regime of increased ductility during deformation is observed.

Creating p–n junctions using semiconducting polymers has proved to be challenging because of difficulties in depositing semiconducting polymer films. Now, by using a cationic conjugated-polymer electrolyte and a neutral conjugated-polymer layer, devices with a fixed bilayer organic p–n junction and fast response times have been fabricated.

In most suspensions viscosity decreases with increasing shear rate. The opposite effect, shear thickening, is a problem for industrial applications. An understanding of how particle interactions in suspensions influence shear thickening may lead to a solution of this problem through the design of smart suspensions.

Small interfering ribonucleic acid (siRNA) is used to silence genes and treat conditions such as human immunodeficiency virus. Safe and efficient delivery, however, is proving problematic. A new class of biologically active siRNA polyelectrolyte complexes based on chemically self-crosslinked siRNA is presented, which shows greatly enhanced gene-silencing efficiencies in vitro and in vivo without significantly eliciting an immune response.

Electron transport through metal–molecule contacts greatly affects the operation of electronic devices based on organic semiconductors and single-molecule junctions, but the nature of the contact barrier remains poorly understood. Scanning tunnelling microscopy experiments reveal a significant variation on the submolecular scale, leading to a scheme to locally manipulate the potential barrier of the molecular nanocontacts with atomic precision.

Why does the bandgap in semiconducting carbon nanotubes depend on the way it is measured? It is now shown that the results obtained by scanning tunnelling spectroscopy are usually influenced by screening, which creates the discrepancy with optical measurements. The results highlight the importance of many-body effects in the electronic properties of carbon nanotubes.

The ability to control the surface chemistry of silicon is important for microelectronic applications. Chemical species can now be stabilized on Si(111) surfaces using a partially alkoxylated surface as a nanopatterning template.

Control of magnetization in ferromagnetic metals can be achieved through the spin torque of currents of spin-polarized electrons, usually injected externally. It is now shown that even without this spin-polarized injection, a current can induce strong spin torques through the Rashba effect. The efficiency of this process makes it a realistic candidate for room-temperature spintronic applications.

Jamming transitions of disordered systems such as foams, gels and colloidal suspensions, describe the change from a liquid to a solid state. An investigation of the three-dimensional properties of jamming shows how, for example, unjamming occurs simultaneously in all directions even if it is induced in one direction only.

Capacitive energy storage is technologically attractive because of its short charging times and its ability to deliver more power than batteries. The capacitive charge-storage properties of mesoporous films of MoO₃ with iso-oriented grains now lead to pseudocapacitive materials that offer increased energy density while still maintaining high power density.