Fabrication of Periodic Arrays of Top-Gathering Titania-organic Hybrid Pillars Derived from Multi-beam Laser Interference

摘要

Multi-beam laser interference (MLI) lithography is known to be one of the fabrication techniques of photonic crystals. In MLI lithography, laser beams are interfered on a scale of the wavelength of light and are irradiated to photosensitive films. We have paid attention to photosensitive TiO_2-organic hybrid film, which has high refractive index. TiO_2-organic hybrid periodic pillar patterns were fabricated by MLI lithography. The TiO_2 hybrid film, which was prepared from Ti-alkoxide and β-diketone by the sol-gel method, was exposed to the interference pattern of femtosecond pulses at 800 nm wavelength. After laser irradiation, the unirradated portion was removed by the development and rinse. Two-dimensional periodic standing alone pillars and 2x2 and 3x3 top-gathering pillars, which were gathered at the top by means of self-organization were formed by changing conditions such as laser irradiation time and film thickness. The pillar patterns depended upon the rinse liquid, the diameter, and the height of pillars. The top-gathering pillars are applicable for diffractive optics.