Kenji Kasahara

Fabrication of high-intensity light-emitting diodes using nanostructures by ultraviolet nanoimprint lithography and electrodeposition

Antireflection nanostructures for GaN light-emitting diodes (LEDs) were fabricated by reactive ion etching (RIE) using Ni as an etching mask. The Ni mask was formed by electrodeposition in combination with ultraviolet nanoimprint lithography (UV-NIL). The antireflection nanostructures of 600 nm in depth, 300 nm in diameter, and 500 nm in pitch were fabricated on a GaN substrate. The radiant intensity of the LEDs was increased 1.5 times compared to that of a conventional LED. Since this method enables the fabrication of wafer-level GaN nanostructures with a low cost process, it is applicable to the fabrication of photonic crystals.

Preparation of epitaxial yttrium–iron garnet micropatterns using metal–organic decomposition with electron-beam irradiation

We have succeeded in obtaining epitaxial yttrium–iron garnet (YIG) micropatterns on a gadolinium-gallium garnet (GGG) substrate by a metal–organic decomposition method with electron-beam (EB) irradiation. We have demonstrated that metal-octylates of Y and Fe showed negative exposure behavior for EB irradiation. X-ray diffraction measurements indicated that the YIG micropatterns were epitaxially well grown on a GGG(111) substrate. The magnetization curve of the YIG micropatterns showed a clear hysteresis loop and the saturation magnetization was estimated to be approximately 100 emu/cm3, which is consistent with that of bulk YIG.