The magnetoelectrochemical switch

In the field of spintronics, the archetype solid-state two-terminal device is the spin valve, where the resistance is controlled by the magnetization configuration. We show here how this concept of spin-dependent switch can be extended to magnetic electrodes in solution, by magnetic control of their chemical environment. Appropriate nanoscale design allows a huge enhancement of the magnetic force field experienced by paramagnetic molecular species in solutions, which changes between repulsive and attractive on changing the electrodes' magnetic orientations. Specifically, the field gradient force created within a sub-100-nm-sized nanogap separating two magnetic electrodes can be reversed by changing the orientation of the electrodes' magnetization relative to the current flowing between the electrodes. This can result in a breaking or making of an electric nanocontact, with a change of resistance by a factor of up to 103. The results reveal how an external field can impact chemical equilibrium in the vicinity of nanoscale magnetic circuits

Transient Quantum Trapping of Fast Atoms at Surfaces

International audienceWe report on the experimental observation and theoretical study of the bound state resonances in fast atom diffraction at surfaces. In our studies, the He4 atom beam has been scattered from a high-quality LiF(001) surface at very small grazing incidence angles. In this regime, the reciprocal lattice vector exchange with the surface allows transient trapping of the 0.3–0.5 keV projectiles into the quasistationary states bound by the attractive atom-surface potential well which is only 10 meV deep. Analysis of the linewidths of the calculated and measured resonances reveals that prior to their release, the trapped projectiles preserve their coherence over travel distances along the surface as large as 0.2  μm, while being in average only at some angstroms in front of the last atomic plane

The coadsorption and interaction of molecular icosahedra with mercury

We have investigated the changes in the electronic structure of molecularly adsorbed orthocarborane films, as a function of Hg co-adsorption, using photo emission. The interaction between Hg and molecular orthocarborane is weak and results in the formation of some small aggregates of Hg. This behavior is very different from alkali metals interaction with molecular carborane films and the interaction of Hg with semiconducting boron carbide films. Hg doping of semiconducting boron carbide may decrease the activation barrier for intrinsic carrier mobility, but does not significantly increase the number of carriers

Evidence for multiple polytypes of semiconducting boron carbide (C2B10) from electronic structure

Boron carbides fabricated via plasma enhanced chemical vapour deposition from different isomeric source compounds with the same C2B10H12 closo-icosahedral structure result in materials with very different direct (optical) band gaps. This provides compelling evidence for the existence of multiple polytypes of C2B10 boron carbide and is consistent with electron diffraction results

Surface-grating deflection of fast atom beams

For energetic atomic beams grazingly incident at the surface along the low index directions, fast motion parallel to the surface and slow motion perpendicular to the surface lead to the quantum diffraction pattern in the scattered beam. In this experimental and theoretical joint study we show that when the incident beam is misaligned with respect to an axial channel, the characteristic deformation of the diffraction pattern reflects an overall deflection of the scattered beam from the specular direction. The deflection is maximum for the azimuthal misalignment angles close to the rainbow angle and we show how this effect can be explained with the detailed balance principle relating diffraction of misaligned and perfectly aligned beams. We also demonstrate that using the detailed balance principle the diffraction charts for the incident beams aligned along the axial channel can be reconstructed from the azimuthal incidence angle dependence of the data obtained with misaligned beams.Fil: Zugarramurdi, A.. Universite Paris Sud; Francia. Centre National de la Recherche Scientifique; FranciaFil: Debiossac, M.. Universite Paris Sud; Francia. Centre National de la Recherche Scientifique; FranciaFil: Lunca Popa, P.. Universite Paris Sud; Francia. Centre National de la Recherche Scientifique; FranciaFil: Salazar Alarcon, Leonardo. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); ArgentinaFil: Momeni, A.. Universite de Cergy-Pontoise; FranciaFil: Khemliche, H.. Universite Paris Sud; Francia. Centre National de la Recherche Scientifique; FranciaFil: Roncin, P.. Universite Paris Sud; Francia. Centre National de la Recherche Scientifique; FranciaFil: Borisov, A. G.. Universite Paris Sud; Francia. Centre National de la Recherche Scientifique; Franci

Determination of the geometric corrugation of graphene on SiC(0001) by grazing incidence fast atom diffraction

International audienc

Heteronanojunctions with atomic size control using a lab-on-chip electrochemical approach with integrated microfluidics

A versatile tool for electrochemical fabrication of heteronanojunctions with nanocontacts made of a few atoms and nanogaps of molecular spacing is presented. By integrating microfluidic circuitry in a lab-on-chip approach, we keep control of the electrochemical environment in the vicinity of the nanojunction and add new versatility for exchanging and controlling the junction's medium. Nanocontacts made of various materials by successive local controlled depositions are demonstrated, with electrical properties revealing sizes reaching a few atoms only. Investigations on benchmark molecular electronics material, trapped between electrodes, reveal the possibility to create nanogaps of size matching those of molecules. We illustrate the interest of a microfluidic approach by showing that exposure of a fabricated molecular junction to controlled high solvent flows can be used as a reliability criterion for the presence of molecular entities in a gap. © 2011 IOP Publishing Ltd