Research articles

The resolution of electron microscopy has increased through the years, and scientists have been able to measure progressively lighter elements. The ultimate goal has now been reached with the imaging of hydrogen atoms.

Monte Carlo simulations are performed to study the assembly of polyhedrons into various mesophases and crystalline states. The formation of new liquid-crystalline and plastic-crystalline phases is predicted at intermediate volume fractions and, by correlating these results with particle anisotropy and rotational symmetry, guidelines for predicting phase behaviour are proposed.

One of the key loss mechanisms in the operation of organic solar cells is the separation and extraction of the generated charge carriers from the active region. The use of a ferroelectric layer is now shown to create large internal electric fields, resulting in an enhanced carrier extraction and increased device efficiency.

Low-voltage intercalation anodes for lithium batteries are important for future applications in portable electronics and electric vehicles. Using a combination of computational methods along with powder X-ray- and neutron-diffraction techniques, the intercalation process for Li_1+xV_1−xO₂, in particular the key role of non-stoichiometry in switching on intercalation, is clarified.

The occupation of electronic orbitals on the surface and interface of oxide thin films and heterostructures is a key influence over their properties, including magnetism and superconductivity. A new spectroscopy technique now provides the first quantitative, spatially resolved data of orbital occupation in oxide structures.

Metamaterials show many intriguing properties, which are often limited to a narrow range of frequencies. The demonstration of a low-loss broadband metamaterial at radiofrequencies promises applications as enhanced antennas, for example.

Electronic devices based on complex oxides offer the possibility to connect electrical devices with phenomena such as magnetism and superconductivity. However, existing oxide field-effect transistors have drawbacks such as high operation voltage. The demonstration of a metal-base transistor whose geometry makes use of the strong internal electric fields in oxide heterojunctions may now offer a new platform for oxide electronics.

A one-pot, high-throughput method for the recombinant polymerization of monomer DNA sequences is reported. The method enables the rapid synthesis of diverse libraries of artificial repetitive polypeptides, exemplified by the isolation of protease-responsive polymers and a family of polypeptides with reversible thermally responsive behaviour.

Devices that can field-ionize gas molecules at low bias voltages are promising for selective gas-sensing applications and for ion-mobility spectrometry. Field ionization is now observed at very low voltage on semiconducting whiskered silicon nanowires.

The control over phase transitions in complex oxides offers the possibility to control their electronic and structural properties. The discovery of a new route to ultrafast photoswitching of manganites via high-energy ‘hidden’ excited states offers the possibility of phase transitions free from thermal effects.

Transmission electron microscopy (TEM) has reached unprecedented resolution and can provide structural information down to the single atomic level. It is now shown that a properly designed experimental analysis also allows the charge distribution around a single atomic dopant to be monitored, demonstrating the possibility of TEM to provide electronic as well as structural information.

Considerable attention has been given in the past few years to two-dimensional electron gases formed at the interface between two bulk insulators. It is now shown that a similar electronic system can be created on the surface of an oxide insulator simply by exposure to UV light.

Metallic glasses are strong but at the same time are brittle once they yield. A new Pd-based metallic glass now shows significantly enhanced fracture toughness. The unique combination of yield strength and toughness makes this glass comparable to the toughest as well as strongest materials known.

Is friction dominated by electrons or by lattice vibrations? A nano-contact experiment shows that on a Nb surface friction drops by a factor of three when crossing the superconductivity transition, showing that it has essentially an electronic nature in the metallic state, whereas the phononic contribution dominates in the superconducting state.

Phase-change materials are key components in rewritable optical disks and are promising for non-volatile electronic memories. The very different structure and ultrafast recrystallization dynamics of another class of phase-change materials, Sb–Te-based alloys, now suggests their use in future memory applications.

Actin networks are an excellent model system for studying the mechanical properties of the cell cytoskeleton. Using microscopic methods, actin bundle networks formed in the presence of the crosslinking protein fascin show age-dependent changes in their viscoelastic properties and spontaneous relaxation dynamics in a similar way to glassy, soft materials.

Phase-change materials are used in computer memories for their switching between amorphous and crystalline phases. However, even the crystalline state shows disorder, with extremely small electron mean free paths. The discovery that, depending on annealing temperature, this disorder leads to a metal–insulator transition in the crystalline phase provides a completely new look at the transport properties of these compounds.