Fabrication of two-dimensional periodic TiO2 pillar arrays by multi-beam laser interference lithography

Hiroyo Segawa,Hiroaki Misawa

doi:10.4236/ns.2009.13022

Hiroyo Segawa, Hiroaki Misawa

Open Access

https://doi.org/10.4236/ns.2009.13022

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Abstract

Two-dimensional (2D) periodic TiO2 pillar arrays, applicable to photonic crystals and micro-channels, were fabricated by direct patterning of a TiO2-organic hybrid material by multi-beam laser interference lithography and calcination of hybrid patterns. 2D periodic pillars of a TiO2– organic hybrid material were prepared by irra-diation with the interference pattern of femto-second laser beams and removal of the non- irradiated portions. Two types of periodic pillar arrays, standing pillars and top-gathering pillars (four pillars gathered at the top), were obtained, depending on laser irradiation conditions. After calcination of TiO2–organic hybrid pillars, TiO2 pillar arrays were obtained without collapse.

Highlights

IntroductionTwo-dimensional (2D) periodic arrays of dielectric materials with submicrometer to micrometer repetitions have great potential in various applications, such as diffraction gratings [1], photonic crystals (PCs) [2,3], and molecular separation in a microchannel [4,5]
Two-dimensional (2D) periodic arrays of dielectric materials with submicrometer to micrometer repetitions have great potential in various applications, such as diffraction gratings [1], photonic crystals (PCs) [2,3], and molecular separation in a microchannel [4,5]. Most of these arrays are fabricated by lithography, in which dielectric materials are coated with photoresists, the photoresist patterns are fabricated by beams such as electron beams, lasers, and beams of UV light, and the patterns of the dielectric material are chemically etched in the area not covered by the photoresist
The refractive index of the pillars might be larger than that of the film, since the pillars appear dense. These results indicate that patterning of photosensitive hybrid materials by lithography and calcination of hybrid materials are excellent methods of creating fine patterns with high aspect ratios in ceramics

Summary

Introduction

Two-dimensional (2D) periodic arrays of dielectric materials with submicrometer to micrometer repetitions have great potential in various applications, such as diffraction gratings [1], photonic crystals (PCs) [2,3], and molecular separation in a microchannel [4,5] Most of these arrays are fabricated by lithography, in which dielectric materials are coated with photoresists, the photoresist patterns are fabricated by beams such as electron beams, lasers, and beams of UV light, and the patterns of the dielectric material are chemically etched in the area not covered by the photoresist. The patterns of the dielectric materials do not feature a high aspect ratio (pattern height to pitch), and complex patterns, e.g.,threedimensional (3D) patterns, cannot be obtained because dielectric materials are generally stable for chemical etchants Patterns such as pillars [6,7], waveguides [8, 9,10], and diffraction gratings [11], can be fabricated in organic–inorganic hybrid materials by direct lithography.

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