Volume 8 Issue 3, March 2009

Two independent studies demonstrate how control over magnetic molecules on surfaces may lead to new spintronics applications.

Preparation of supported subnanometre platinum clusters that are stable provides a new design strategy for industrial nanocatalysts.

The discovery that domain walls in insulating thin films of the multiferroic compound BiFeO₃ are electrically conducting opens the door for a number of possible applications.

The melting of transition metals on compression is a challenging topic. Computer simulations suggest that hot-compressed tantalum becomes a one-dimensional, liquid-like glass, with important implications for understanding planetary interiors.

Large and homogeneous layers of graphene are obtained by annealing silicon carbide in a dense noble gas atmosphere that controls the way in which silicon sublimates. Epitaxial graphene thus gets back on track towards future electronic applications.

Biological membranes form an extremely complex and dynamic network in cells, guided by specialized protein machinery. A new algorithm analyses membrane shape to extract forces applied by proteins controlling the membranes.

Although magnetic molecules are widely investigated for their potential use in memory devices, their regular arrangement on surfaces has proven difficult. Arrays of iron atoms, linked by molecular ligands, have now been fabricated on copper surfaces. Importantly, the magnetism of the iron atoms is preserved and can be switched through oxygen adsorption.

Molecular magnets are promising for their use as high-density memory devices. However, maintaining the molecules’ magnetic state when bonded to a substrate has been impossible. The discovery, in sophisticated experiments, that single magnetic molecules can indeed show magnetic hysteresis when wired to a gold surface opens the door to individually address magnetic molecules.

The possibility of polarizing conducting charges in a material by blocking those with a specific spin direction could lead to efficient spintronic devices. It is now shown that spin polarized-defects in a non-magnetic semiconductor can deplete electrons with opposite spins and turn the semiconductor into an efficient spin filter operating at room temperature.

Thermal annealing of SiC produces graphene layers on an insulating substrate, but the material is highly inhomogeneous. It is now shown that an argon atmosphere during annealing improves uniformity of the graphene layers dramatically and yields better transport characteristics. This is a very important result for the development of graphene-based electronic devices.

A limiting factor of the power conversion efficiencies of organic photovoltaic devices is low voltage output. Methano derivatives of the trimetallic endohedral fullerene Lu₃N@C₈₀ have now been synthesized and used as the acceptor in organic photovoltaics. The open circuit voltage of the devices is significantly above those made using alternative fullerenes.

Catalytic oxidative dehydrogenation of alkanes is limited by poor activity and/or selectivity. Efficient conversion of propane to propylene is now achieved using sub-nanometre Pt clusters stabilized on alumina supports. The clusters are shown to be substantially more active than conventional catalysts and are highly selective towards propylene formation.

Mesoporous materials with tunable, non-oxidic frameworks possess structural characteristics that make them attractive for catalytic and optoelectronic applications. Porous materials based on germanium-rich chalcogenide networks and polarizable surfaces exhibit selectivity for separating hydrogen from methane and carbon dioxide.

The melting of transition metals at high pressures has been subject to intensive debate, given seemingly contradictory experimental evidence. Molecular dynamics calculations now demonstrate how, at high pressure, shear induces a transition from body-centred-cubic tantalum to a one-dimensional structure, offering a plausible explanation for experimental observations.

Domain walls may be important in future electronic devices, given their small size as well as the fact that their location can be controlled. In the case of insulating multiferroic oxides, domain walls are now discovered to be electrically conductive, suggesting their possible use in logic and memory applications.

Graphene nanostructures—like nanoribbons or quantum dots—hold great potential for applications. An extensive STM study elucidates how the details of the nanostructure edges heavily influence the electronic properties, which can vary between metallic and semiconducting according to the predominancy of zigzag or armchair edges.