Takatoshi Nagano

Large constriction of lattice constant in epitaxial magnesium oxide thin film: Effect of point defects on lattice constant

Epitaxial thin films prepared using an MgO target on silicon substrate often show constriction of lattice constant (a∼4.1u2002A). Detailed investigation of the crystal structure excluded the possibility that the epitaxial films are either cubic spinel MgO or magnesium silicate (a/2∼4.1u2002A). With such a constriction in rock salt MgO structure point defects must be induced into structure. An ab initio method with semicore pseudopotentials predicted such constrictions on configurations of Schottky type defects. The Schottky defects with random distribution throughout lattice cites satisfied constricted lattice constant, mass density, and crystallography experimentally observed on the epitaxial MgO films.

Nano-structure-controlled very low resistivity Cu wires formed by high purity electrolyte and optimized additives

Resistivity increase in nano-level Cu wires is becoming a critical issue for high speed ULSIs. We have established the new manufacturing process utilizing very high-purity 9N electrolyte and optimized additives to control nano-structures of Cu wires, and we realized Cu wires with resistivity 50% lower than that of wires made by a conventional process. We also have ascertained the reason for getting very low resistivity Cu wires by STEM analyses and first-principle simulation.

Properties of epitaxial AlN thin film deposited on sapphire substrate by ECR plasma

We prepared AlN film on c-plane sapphire substrate by electron cyclotron resonance plasma-enhanced sputtering deposition (ECR-sputtering). X-ray diffraction (XRD) verified the epitaxial growth of AlN films with the full width at half maximum (FWHM) of rocking curve of 0.04 deg. even on the film thickness of 100 nm. XRD also verified slight change of peak position from AlN film along both out of plane and in-plane directions.