Articles in 2010

The manipulation of spin states is a key requirement in spintronics. In semiconductor microcavities, a multistate switching of the spin state of polaritons, which form as a result of the coupling of photons and excitons in the microcavity, may lead to new spintronics devices.

The control of magnetic properties by electric fields is key to realizing spintronics devices. The surface of the antiferromagnetic magnetoelectric Cr₂O₃ is now shown to exhibit room-temperature ferromagnetism, whose direction can be switched by an electric field. This magnetization switches the exchange-bias field with magnetic multilayers grown on Cr₂O₃, promising a new route towards room-temperature spintronics devices.

Peptide-based molecules that self-assemble into lamellar plaques with fibrous texture on heating, subsequently break on cooling to form long-range aligned bundles of nanofibres. This thermal route to monodomain gels is compatible for living cells and allows the formation of noodle-like viscoelastic strings of any length.

There has been an intense search in recent years for long-lived spin-polarized carriers for spintronics and quantum computing devices. It is now shown that spin-polarized quasiparticles in superconducting aluminium layers have surprisingly long spin lifetimes, nearly a million times longer than in their normal state.

The formation of lithium dendrites on the metal electrode surface of lithium batteries can lead to short circuits, making them potentially unsafe and unusable. The use of in situ NMR spectroscopy provides time-resolved and quantitative information about the nature of metallic lithium deposited on lithium-metal electrodes.

Tailoring the thermal conductivity of nanostructured materials is a fundamental challenge for nano- and microelectronics heat management. It is now demonstrated how to modify the thermal conductivity of SiGe by engineering nanodot inclusions in regions as short as 15 nm. A similar approach could used on other materials, extending the range of thermal conductivities available.

An organic light-emitting transistor has now been fabricated with a trilayer heterostructure. This architecture is shown to prevent both photon loss at the electrodes and exciton-charge quenching, thereby dramatically improving device efficiency and establishing these types of transistor as a promising alternative to organic light-emitting diodes.

The fact that cells sense and respond to the mechanical properties of their environment is now a well-explored concept, although the mechanism of this response is still unknown. Now it is shown that cells themselves can mechanically manipulate the materials surrounding them by pulling at connective points, providing a feedback loop to influence cell fate.

Understanding the interaction of water with oxide surfaces at the molecular level could prove to be significant for controlling the catalytic activity of complex nanoparticles on insulating films. Two types of selective dissociation pathway involving electronic and vibrational excitation are now observed for a single water molecule on MgO thin films.

Electronics that are capable of intimate integration with the surfaces of biological tissues create opportunities for improving animal/machine interfaces. A bio-interfaced system of ultrathin electronics supported by bioresorbable silk-fibroin substrates is now presented. Mounting such devices on tissue and then allowing the silk to dissolve initiates a conformal wrapping process that is driven by capillary forces.

Despite recent advances in lithium batteries, fundamental issues of practical importance such as energy efficiency have not been adequately considered. A general model for the occurrence of inherent hysteretic behaviour in insertion storage systems containing multiple particles is now proposed.

Peptoids are synthetic polymers designed to mimic the structure and functionality of proteins. When a one-to-one blend of two oppositely charged peptoids is mixed in solution, giant, 2.7-nm-thick free-floating sheets are formed. The sheets can specifically bind a corresponding protein, and offer potential for producing functional two-dimensional nanostructures in the future.

Viscoelastic gels can be made by using flow to induce structure into solutions containing surfactant micelles. However, the gels disintegrate soon after flow stoppage. By using a microfluidic-assisted laminar-flow process to generate very high extension rates, it is now shown that permanent gels can be made, creating new opportunities for applications.

Silicon-based lithium-ion batteries are attractive because in principle they offer higher specific capacities than conventional graphite. A hierarchical bottom-up approach is now used to prepare lithium-ion anodes with improved reversible capacities and stable electrochemical performance.

Counterintuitively, the exceptional strength of silks comes from β-sheet nanocrystals in which the key molecular interactions are weak hydrogen bonds. Simulations now show that nanoconfinement effects make β-sheet nanocrystals the size of a few nanometres stiffer, stronger and tougher than larger ones. These effects can be exploited to create materials with superior mechanical properties.

An exothermic chemical reaction coupled with a one-dimensional conductor has been predicted to give rise to self-propagating waves with high thermal conductivity. This is now demonstrated experimentally with carbon nanotubes used as guides for the waves, which propagate with high thermal conductivity and with electric pulses of very intense power.

Controlling the magnetic properties of a materials system by electric means can lead to efficient electronic and memory devices. Now, for the first time, the control of ferromagnetism by the application of an electric voltage is demonstrated in germanium quantum dots for temperatures up to 100 K.

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.

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.