S. Inoue

Imprinting characteristics by photo-induced solidification of liquid polymer

Imprinting lithography is the most promising technology in terms of mass-production and low-cost of equipment, but thermal cycle above the glass transition temperature (more than 100/spl deg/C) will worsen positional accuracy in stitching and overlay of patterns. In this paper, we describe the imprinting process using liquid polymer, which is solidified with Ultra-violet (UV) light exposure.

Epitaxial growth of GaN on copper substrates

We have grown GaN films on Cu(111) substrates using pulsed laser deposition. We have found that GaN(0001) grows epitaxially on Cu(111) when employing low temperature grown AlN buffer layers with an in-plane epitaxial relationship of AlN[112¯0]‖Cu[11¯0] Reflection high-energy electron diffraction images have exhibited sharp streaky patterns, indicating that GaN grows with a flat surface. Electron backscattering diffraction observations have revealed that neither 30° rotational domains nor cubic phase domains exist in the GaN films. Spectroscopic ellipsometry measurements have shown that the heterointerfaces in the GaN∕AlN∕Cu structure are abrupt. The epitaxial growth of GaN on Cu substrates is likely to raise the power limit for future light emitting and electron devices due to the high thermal conductivity of Cu.

Growth of single crystalline GaN on silver mirrors

GaN films have been grown on highly thermally conducting Ag(111) substrates by using pulsed laser deposition. GaN(0001) grows epitaxially on Ag(111) with an in-plane epitaxial relationship of GaN[112¯0]‖Ag[11¯0] when low temperature AlN buffer layers are used. The heterointerfaces in the AlN∕Ag structure are atomically abrupt, and that the abruptness remains unchanged during annealing up to 700°C for the GaN growth. Neither 30° rotational domains nor cubic phase domains exist in the GaN films. It has been also confirmed that the GaN films grown on the Ag substrate exhibit strong near band edge photoluminescence emission at 3.51eV. These results indicate that the epitaxial growth of GaN on mirror-polished single crystalline Ag substrates possibly improve the power limits and the light extraction efficiency of future light-emitting devices.

Epitaxial growth of GaN films grown on single crystal Fe substrates

GaN films have been grown on single crystalline Fe(110), Fe(100), and Fe(111) substrates with low-temperature AlN buffer layers by the use of pulsed laser deposition. AlN films with 30° rotated domains and polycrystalline AlN films grow on Fe(100) and Fe(111), respectively. On the other hand, AlN(0001) films grow epitaxially on Fe(110) substrates. X-ray reflectivity measurements have revealed that the heterointerface of AlN∕Fe(110) is quite abrupt and that its abruptness remains unchanged, even after annealing at 700°C. GaN epitaxial films have been grown on AlN∕Fe(110) structures with an in-plane relationship of GaN[11−20]∥AlN[11−20]∥Fe[001]. The first-principles calculations have revealed that this in-plane epitaxial relationship is determined by the adsorption process of nitrogen atoms on the Fe surfaces at the initial stage of the growth.

Epitaxial growth of AlN films on Rh ultraviolet mirrors

Epitaxial growth of AlN films on mirror polished Rh(111) substrates, with high reflectivity in the ultraviolet (UV) region and high thermal conductivity, was demonstrated using a low temperature growth technique employing pulsed laser deposition. It was found that AlN(0001) grows epitaxially on Rh(111) at 450°C with an in-plane epitaxial relationship of AlN[112¯0]‖Rh[11¯0] Electron backscattering diffraction observations revealed that neither 30° rotational domains nor cubic phase domains were present in the AlN. X-ray reflectivity measurements revealed that no interfacial layer was present between the AlN films and Rh substrates and that the heterointerface was atomically abrupt, indicating that the Rh substrate still functioned as an UV mirror, even after AlN growth.

Observation of magnetic domain structure in anatase (Ti,Co)O2 thin film at room temperature

Magnetic domain structures in anatase (Ti,Co)O2 (001) epitaxial thin films were observed at room temperature. Magnetic force microscopy in vacuum enabled to observe submicrometer-sized maze domain. Variation of magnetic domain structure as functions of carrier density and Co content was in accordance with that of macroscopic magnetization representing close relationship between the bulk magnetism and magnetic domain structure. With increasing carrier density and/or Co content, the magnetic domain became larger with larger magnetic force signal mostly, where the ferromagnetic transition at carrier density of ∼2 × 1019 cm−3 was observed as an emergence of magnetic domain structure. Micromagnetic parameters were evaluated as functions of carrier density and Co content.

Molecular Weight Dependence of Dielectric Behavior of Polymer Electrolytes under Shear Flow

We have developed a new apparatus for measuring dielectric relaxation under shear flow, and applied it to a typical polymer electrolyte system, polypropylene oxide (PPO)-lithium perchloride, while changing the molecular weight of PPO. We observed a drastic increase in dielectric increment Δe and a drastic decrease in conductivity σ with increasing shear rate. The molecular weight dependence of σ and the relaxation time τ suggests that the conductivity is due to ion transport assisted by the conformational change of the entire polymer chain and the permittivity is ascribed to the ion fluctuation within a single chain assisted by the segmental motion of a polymer. On applying shear flow, the conformational change of a polymer chain is strongly suppressed, which would cause the decrease in conductivity.