Yuta Takahashi

Magnetic trapping of superconducting submicron particles produced by laser ablation in superfluid helium

We produced spherical superconducting submicron particles by laser ablation of their base metal tips in superfluid helium, and trapped them using a quadrupole magnetic field owing to the diamagnetism caused by the Meissner effect. We also measured their critical temperatures of superconductivity, by observing the threshold temperatures for the confinement of superconducting submicron particles in the trap.

Property of magnetic trapping of superconducting sub-micron particles

We have produced superconducting sub-micron particles by laser ablation in superfluid helium and trapped them using quadrupole magnetic field due to the diamagnetism.

Optical fabrication and trapping of superconducting nanoparticles in superfluid helium (Conference Presentation)

Superfluid helium having extremely low temperature, negligibly small viscosity, and huge thermal conductivity provides us a unique opportunity to generate a novel cryogenic space for the fabrication of nanostructures and the manipulation of their motion. Here we fabricated metallic nano- and micro-particles by laser ablation in superfluid helium and selectively trapped superconducting particles with a quadrupole magnetic field utilizing perfect diamagnetism caused by Meissner effect. We also discuss the size dependence of the superconducting transition temperatures of the trapped metallic particles by changing the temperature of liquid helium.

Deposition of tetracene thin films on SiO2/Si substrates by rapid expansion of supercritical solutions using carbon dioxide

We report on a novel deposition technique of tetracene (naphthacene) thin films on SiO2/Si substrates by rapid expansion of supercritical solutions (RESS) using CO2. Optical microscopy and scanning electron microscopy show that the thin films consist of a high density of submicron-sized grains. The growth mode of the grains followed the Volmer–Weber mode. X-ray diffraction shows that the thin films have regularly arranged structures in both the horizontal and vertical directions of the substrate. A fabricated top-contacted organic thin-film transistor with the tetracene active layer showed p-type transistor characteristics with a field-effect mobility of 5.1 × 10−4 cm2 V−1 s−1.