Ryo Matsumoto

Note: Novel diamond anvil cell for electrical measurements using boron-doped metallic diamond electrodes.

A novel diamond anvil cell suitable for electrical transport measurements under high pressure has been developed. A boron-doped metallic diamond film was deposited as an electrode on a nano-polycrystalline diamond anvil using a microwave plasma-assisted chemical vapor deposition technique combined with electron beam lithography. The maximum pressure that can be achieved by this assembly is above 30 GPa. We report electrical transport measurements of Pb up to 8 GPa. The boron-doped metallic diamond electrodes showed no signs of degradation after repeated compression.

Observation of zero resistance in as-electrodeposited FeSe

Abstract Superconducting FeSe films were electrochemically deposited on rolling-assisted biaxially textured substrate (RABiTS) tape. We observed zero resistivity in the as-electrodeposited FeSe film prepared on the RABiTS when the appropriate voltage was applied while it was dipped into the solution. When the RABiTS tape was dipped in the solution without applying voltage, a thin Se film was deposited on the substrate. The compositional ratio of the FeSe film got closer to the stoichiometric ratio with decreasing the dipping time before applying voltage.

Superconducting joints using Bi-added PbSn solders

Superconducting joints between NbTi and Bi2Sr2Ca2Cu3O10 superconducting wires were successfully fabricated using Bi-added PbSn solders with an in situ sheath-dissolution technique without a removal process for the sheath materials. A backscattered electron image and an energy-dispersive X-ray spectroscopy analysis of the cross-sectional plane of the joints revealed that the joints using Bi-added PbSn solder had a homogeneous morphology with tiny non-superconducting islands. The superconducting joints exhibited high critical currents above 200 A in self-field and 50 A under an applied magnetic field of 5 kOe.

Observation of a Pressure-Induced Phase Transition for Single Crystalline LaO0.5F0.5BiSeS Using a Diamond Anvil Cell

A pressure-induced phase transition in LaO0.5F0.5BiSeS is demonstrated by performing resistance measurements with a diamond anvil cell. The superconducting transition temperature (Tc) of LaO0.5F0.5BiSeS changes from a low-Tc phase (4.9 K) to a high-Tc phase (7 K) owing to the application of pressure up to 5.1 GPa.

Synthesis of LaO0.5F0.5BiS2 nanosheets by ultrasonification

Abstract LaO0.5F0.5BiS2 nanosheets were produced by ultrasonification. A slightly reddish colloidal suspension was obtained by ultrasonification of LaO0.5F0.5BiS2 powder in ethanol. Transmission electron microscope (TEM) images of the dried suspension indicated the nanosheet morphology of LaO0.5F0.5BiS2, and the electron diffraction spots indicated 4-fold symmetry. The thickness of the sheets was 2–6 nm, which corresponded to 2–4 unit cells of the c-axis of LaO0.5F0.5BiS2.

Diamond anvil cell using metallic diamond electrodes

A novel diamond anvil cell specialized for resistivity measurements under high pressure have been developed. Boron-doped metallic diamond electrodes were deposited onto a nano-polycrystalline diamond anvil using a microwave plasma-assisted chemical vapor deposition technique combined with electron beam lithography. The various designs of boron-doped metallic diamond electrodes were demonstrated, and they showed no signs of degradation after repeated compression.