Shinpei Iijima

Hexagonal polymorph of tantalum–pentoxide with enhanced dielectric constant

A tantalum–pentoxide dielectric with an enhanced permittivity of over 50 was found to be crystallized in a hexagonal symmetry with a=0.628 nm and c=0.389 nm. The incommensurate epitaxy of tantalum pentoxide on hcp-ruthenium metal stabilizes the hexagonal phase with √3-time periodicity in plane, as compared with that of the known hexagonal δ phase. The crystallographic assumption, which is based on one-dimensional Ta–O–Ta chain along the c axis, can explain large polarizability caused by delocalized electrons on the one-dimensional chain.

Photostimulated evaporation of SiO2 at room temperature by undulator irradiation and its dependence on sample fabrication

Abstract Ablation of SiO 2 films by irradiation of undulator light was examined on samples fabricated by chemical vapor deposition (CVD) and thermal oxidation of silicon. CVD samples having different values of x in SiO x were prepared by changing the mixture ratio of SiH 4 and N 2 O. The ablation rate increased of value of x in SiO x . Thermal growth oxide of silicon was also ablated by undulator irradiation at room temperature. The ablation rate increased with increasing excitation energy.