Amorphous carbon pillars grown by focused ion beam induced chemical vapor deposition (FIB-CVD) had been considered to form in a cylindrical double structure. In this structure, the core containing Ga originating from the primary ion is surrounded by an amorphous carbon shell grown by the secondary electrons that were emitted during the inelastic scattering process of the primary ions penetration. We measured the Young's modulus in a series of inclined pillars; the thickness of the pillars was reduced with the inclination. However, the Young's modulus of the inclined pillars of thinner diameter increased. Here, we found that such FIB-CVD pillars had an elastic double structure that is comprised of a very stiffened core with 300 GPa of Young's modulus, and an extremely soft shell having 30 GPa of Young's modulus. We also confirmed that the oxygen plasma thinning of the perpendicular pillars considerably increased the Young's modulus of the FIB-CVD pillars.

We demonstrated a new process for synthesizing a graphene sheet at the interface between solid amorphous carbon and liquid gallium. The insolubility of carbon in gallium strongly restricted the depth of graphitization, but a multilayered graphene sheet having four to six layers of graphene was produced over the entire area of the interface immediately beneath the liquid gallium. We also demonstrated the operation of an electric-field-effect device fabricated on the multilayered graphene with a back-gated configuration, and a maximum conductance modulation of 40% was observed for an applied gate voltage ranging from -100 to +100 V.

A method for fabricating single-crystalline nanogaps on Si substrates was developed. Polycrystalline Pt nanowires on Si substrates were broken down by current flow under various gaseous environments. The crystal structure of the nanogap electrode was evaluated using scanning electron microscopy and transmission electron microscopy. Nanogap electrodes sandwiched between Pt-large-crystal-grains were obtained by the breakdown of the wire in an O(2) or H(2) atmosphere. These nanogap electrodes show intense spots in the electron diffraction pattern. The diffraction pattern corresponds to Pt (111), indicating that single-crystal grains are grown by the electrical wire breakdown process in an O(2) or H(2) atmosphere. The Pt wires that have (111)-texture and coherent boundaries can be considered ideal as interconnectors for single molecular electronics. The simple method for fabrication of a single-crystalline nanogap is one of the first steps toward standard nanogap electrodes for single molecular instruments and opens the door to future research on physical phenomena in nanospaces.

Although carbon has been recognized to be insoluble in gallium, we found that the outermost surface of gallium has unexpectedly high carbon solubility, particularly the limited region of about a few nanometers in depth. Our in-situ transmission electron microscope observations revealed that a graphene layer was precipitated at the surface of a gallium droplet simultaneously with gallium evaporation, and some of the droplets created an internal graphitic layer. On the basis of these experimental data, we evaluated a substantial carbon solubility that seemed to exceed about 50 at. %, but was realized in a very thin surface region of about 4 nm in depth. We believe that this high carbon solubility at the gallium surface is the key mechanism for the catalytic ability of gallium that was observed at the interface between liquid gallium and solid amorphous carbon.

[1] We carried out a wind tunnel experiment on aeolian transport of sand. Fluorescencedyed grains of sand were embedded in the sand bed in a wind tunnel, and their dispersion was recorded by a video camera. Dispersion of colored sand both downwind and in the crosswind direction are examined. The concentration of colored sand decreases as an exponential function of the downwind distance y, Ae Àky , whereas the cross-sectional distribution is approximated by a Gaussian distribution with the standard deviation proportional to ffiffi ffi y p . The characteristic length scale is 1000 times greater in the downwind than in the crosswind direction. A simple stochastic model is proposed to explain these findings. We also found that our experimental results conform to the assumptions of the Werner model, which reproduces aeolian dune dynamics well. We derived conditions on the parameters of the Werner model from the experimental results and suggest the applicability of the Werner model to real problems such as sandy coasts, deserts, and regions whose surface is contaminated.

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Magnetic shielding is a key technology for superconducting radio frequency (RF) cavities. There are basically two approaches for shielding: (1) surround the cavity of interest with high permeability material and divert magnetic flux around it (passive shielding); and (2) create a magnetic field using coils that cancels the ambient magnetic field in the area of interest (active shielding). The choice of approach depends on the magnitude of the ambient magnetic field, residual magnetic field tolerance, shape of the magnetic shield, usage, cost, etc. However, passive shielding is more commonly used for superconducting RF cavities. The issue with passive shielding is that as the volume to be shielded increases, the size of the shielding material increases, thereby leading to cost increase. A recent trend is to place a magnetic shield in a cryogenic environment inside a cryostat, very close to the cavities, reducing the size and volume of the magnetic shield. In this case, the shielding effectiveness at cryogenic temperatures becomes important. We measured the permeabilities of various shielding materials at both room temperature and cryogenic temperature (4 K) and studied shielding degradation at that cryogenic temperature.