Real graphene on a SiC substrate
Graphene is the name given to an isolated plane of carbon atoms arranged
on a honeycomb lattice. Because of pecular electronic properties, it
could play a major role in tomorrow's nanoelectronics. Graphene can be
grown on a SiC substrate opening a route to carbon based electronics. We
show in our letter that this system indeed has the properties of
isolated graphene thanks to the formation of an interface buffer layer.
Our calculations and X-Ray diffraction measurements evidence that
eventhough the cristallographic structure of this interfacial layer is
very close to the honeycomb lattice, the strong coupling to the
substrate prevents any graphene like behavior in this layer. Graphene
properties are recovered in the first carbon layer on top of the buffer
layer. In agreement with experiment, we find that the graphene layers
are doped and we show that the doping level depends on the interface
geometry. LX10753
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Tuning of tunneling anisotropies by an electric field
The resistance measured in ferromagnetic metals usually depends on
the relative orientation of the magnetization and the current
direction, an effect known as anisotropic magnetoresistance (AMR).
Before the advent of giant magnetoresistance the effect was employed in
read-out heads of hard disks. In our manuscript we describe another
type of anisotropic resistance occurring if a ferromagnetic layer is
incorporated in a ferromagnet/insulator/non-magnetic metal sandwich, in
our case Fe/GaAs/Au with a single crystalline Fe/GaAs interface. There
the resistance which is due to quantum mechanical tunneling of
electrons between the ferromagnetic (Fe) and normal (Au) metal, depends
on the direction of magnetization in the iron film. While the
observation of such a tunneling anisotropic magnetoresistance (TAMR)
came as a surprise, more astonishing is the possibility to tune the
anisotropy. Indeed, the anisotropy can be reversed and even switched
off by means of the applied bias voltage. The experiments can be
perfectly fitted by taking the role of the spin-orbit interaction of
electrons, while tunneling, into account. Apart from potential
application, provided the effect can be increased, e.g. by other
material combinations, the experiment provides a striking experimental
manifestation of the role of spin-orbit interaction in the quantum
mechanical tunnelling process. LY10336
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Phase Transition in Strongly Non-ideal Deutherium Plasma, Generated by Quasiisentropical Compression at Megabars.
High-explosive (HE) driven generators of cylindrical and plane shock waves in D2 and H2 were used for generation of warm and dense strongly non-ideal matter with intense inter-particle interaction and Fermi statistics. For the first time highly resolved flash X-ray diagnostics were used for measuring the adiabatic plasma compressibility. The thermodynamic measurements demonstrated the twenty percent increase of density at megabar pressure, just in the density range, where the electrical measurements indicated sharp - five order of magnitude - increase of electrical conductivity due to pressure ionization in strongly coupled plasmas. We think we have obtained the first direct experimental signature of the existence of new phase transition in strongly non-ideal hydrogen (deuterium) with intense Coulomb interaction other than the gas-liquid transition and melting of molecular crystal. LY10378
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A chemical survey of the landscape beyond the nanoscale
A team of scientists from Australia and Spain have for the first time demonstrated simultaneous imaging and unambiguous chemical identification of columns of atoms in a solid. This was achieved by scanning the specimen with an atom-sized electron probe at the state-of-the-art SuperSTEM facility in Daresbury, England. Improved data processing techniques and detailed modeling of the imaging process facilitated this major step towards the goal articulated by Richard P. Feynman in his famous talk, Plenty of Room at the Bottom (1959): “It would be very easy to make an analysis of any complicated chemical structure; all one would have to do would be to look at it and see where the atoms are. The only trouble is that the electron microscope is one hundred times too poor... I put this out as a challenge: Is there no way to make the electron microscope more powerful?” Research in nanoscience and technology, design of new materials and drugs, protein structure and folding, to name just a few, are all areas where knowledge of structure and function at the atomic level is essential. LF11130
