Katsuei Ishida

Preparation of twin- and crack-free LiNbO3 films by pulsed laser ablation using nucleation process at high temperature

LiNbO3 films were prepared by pulsed laser ablation with a KrF excimer laser. A novel growth process was employed using nucleation at a high temperature and subsequent film growth at a low temperature. This two-step growth process gave rise to a high-quality LiNbO3 film without twins and cracks. This process is expected to be effective for preparing excellent LiNbO3 films for the waveguide applications.

Rotational honeycomb epitaxy of Ru thin films on sapphire (0001) substrate

Rotational honeycomb epitaxy of hexagonal Ru films was achieved on c-plane sapphire substrates by pulsed laser ablation with the a-axis ratio of √3. The crystal structure and crystallinity of the Ru films were examined by X-ray diffraction and pole figure measurements, respectively. The Ru films were found to be epitaxially grown with an a-axis rotation by 30° around the a-axis of sapphire, resulting in the crystallographic relationship of (0001)Ru // (0001) sapphire and Ru // sapphire. This is because the lattice mismatch between Ru and sapphire is as small as about 1.3%.

Characterization by chemical etching for superconducting Bi2Sr2CaCu2O8 crystals grown by CO2-laser melting

Single crystals are grown directly from the melt in a rough size of (0.5–1.5)×(0.2–0.5)×(0.05–0.1) mm3. Comparing a pair of opposite surfaces created by cleaving, it has been recognized that the microstep line structure with the unit cell steps is generated at the instant of cleaving the crystal. With the aid of chemical etching it has further been clarified that the cleavage plane fractures into terraces hemmed by unit cell steps at crossing spiral dislocations. Simultaneously it has been proved that beak-pits observed among etch figures indicate the outcrop of dislocations. In addition it has been revealed by etching that stacking faults in a plane are involved in the crystal along the crystallographic a-axis.