Hiroyuki Fukuyama

Abstract The N 2 –CO gas annealing technique was demonstrated to improve the crystalline quality of the AlN layer on sapphire. 300-nm-thick AlN layers were fabricated on sapphire substrates by a metal–organic vapor phase epitaxy method. The AlN layers were annealed in N 2 and/or N 2 –CO gas atmosphere at 1923–1973 K for 0.5–4 h. Many pits and voids were observed on the AlN surface annealed in N 2 atmosphere at 1973 K for 2 h. The rough surface was, however, much improved for the AlN annealed in

An electromagnetic levitation technique performed in a static magnetic field was used to measure density, surface tension, normal spectral emissivity, heat capacity, and thermal conductivity of molten 316L stainless steel (SS316L) and SS316L that contained 5 mass % B4C. The addition of 5 mass % B4C to the SS316L yielded reductions of 111 K, 6%, 19%, and 6% in the liquidus temperature, density, normal spectral emissivity, and thermal conductivity at the liquidus temperature of the SS316L, respect

A model of one-dimensional fermions characterized by a large momentum-transfer interaction ${g}_{1}$ and a small momentum-transfer interaction ${g}_{2}$ is considered. Results obtained previously by the renormalization-group method are extended by studying the triplet Cooper-pair response function and uniform charge and spin response functions. The sign of ${g}_{1}$ dominates the behavior of the system. For ${g}_{1}>0$, ${g}_{1}\ensuremath{-}2{g}_{2}>0$ the triplet Cooper response diverges

A tight-binding model Hamiltonian is used to study the electronic properties of the disordered alloy ${A}_{x}{B}_{1\ensuremath{-}x}$. Both the local energy levels and the interatomic transfer integrals are allowed to vary randomly. The problem simplifies considerably if it is assumed that the values of the transfer integrals are additive, i.e., that ${h}^{\mathrm{AB}}=\frac{({h}^{\mathrm{AA}}+{h}^{\mathrm{BB}})}{2}$. In this case the conventional methods of perturbation theory are applicable and

This study is a fundamental investigation aimed at developing a new noncontact modulated laser calorimetry method incorporating a static magnetic field to achieve measurement of the true thermal conductivity of a metallic melt. For establishing the experimental principle, a solid platinum sphere was used in this study. The sphere positioned in the centre of a radio frequency coil was heated sinusoidally by a laser; its temperature response was monitored. Analyses of the temperature amplitude and

Single crystalline aluminum nitride (AlN) is a key material for deep-ultraviolet light emitting devices. In the present study, high-quality single crystalline AlN films have been fabricated by nitriding α-Al2O3 with a precise control of driving force of nitridation reaction. This process provides the ⟨0001⟩-axis oriented AlN film as large as 50.8mm in diameter formed on (0001) and (112¯0) planes of α-Al2O3 substrates. The crystalline qualities of the films have the values of full width at half m

A new synthetic method of forming the gamma‐phase of aluminum oxynitride (alon) has been proposed. alon has been successfully synthesized by the DC nitrogen plasma arc using alpha‐Al 2 O 3 and AlN as starting materials. Alon rapidly forms in a liquid state under thermal plasma. The obtained lattice parameter of alon has been determined as a function of the concentration of Al 2 O 3 . Evaporation takes place during arc melting. The condensed alon from the vapor consists of nanoscale‐sized spheric

The normal spectral emissivities at 807 and 940 nm, heat capacities at constant pressure and thermal conductivities of Pd and Ti melts were measured using an electromagnetic levitation technique in a static magnetic field. The static magnetic field suppresses the surface oscillation, translational motion, and convection flow on electromagnetically levitated samples. The convections in the levitated Pd and Ti melts were suppressed sufficiently for thermal conductivity measurement by the static ma

We argue that at low temperatures and large magnetic fields, Coulomb correlations among the electrons in two-dimensional structures determine the recently observed temperature dependence of the quantum Hall measurements for the highest fields.

The authors previously developed a sapphire nitridation method using carbon-saturated N2–CO gas mixture to form a high-quality AlN film for III-nitride-based optoelectronic devices. In this study, the nitridation behavior of (0001) (c) plane and (112¯0) (a) plane sapphire was studied to elucidate and optimize the process at temperatures of 1823 and 1873 K. The AlN film thickness, surface morphology, crystal quality, and interfacial phenomena were investigated as functions of nitridation time and