Fabrication of Periodic Arrays of Nano-sized Si and Ni dots on SiO 2 Using Linearly Polarized Nd:YAG Pulsed Laser
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1059-KK08-09
Fabrication of Periodic Arrays of Nano-sized Si and Ni dots on SiO2 Using Linearly Polarized Nd:YAG Pulsed Laser Kensuke Nishioka, and Susumu Horita School of Material Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, 923-1292, Japan ABSTRACT Periodic arrays of nano-sized Si and Ni dots were fabricated by only irradiating a linearly polarized Nd:YAG pulsed laser beam to Si and Ni thin films deposited on silicon dioxide (SiO2) film. The interference between an incident beam and a scattered surface wave leads to the spatial periodicity of beam energy density distribution on the surface of the irradiated samples. A thin film was melted using a laser beam, and the molten film was split and condensed owing to its surface tensile according to the periodic energy density distribution. Then, the fine lines (line and space structure) were formed periodically. After the formation of fine lines, the sample was rotated by 90o, and the laser beam was irradiated. The periodic energy density distribution was generated on the fine lines, and the lines split and condensed according to the periodic energy density distribution. Eventually, the periodically aligned nano-sized dots were fabricated on the SiO2 film. INTRODUCTION It has been reported that linearly polarized laser irradiation induces spatially periodic fine structures on the surfaces of semiconductors, metals, and polymers. The formation of these laserinduced periodic surface structures (LIPSS) indicates that the laser irradiation produces a periodic temperature distribution on the surface of the irradiated samples. For most of the cases, the periodic spacing Λ of the energy density distribution on the surface depends on the wavelength λ and the incident angle θi from the normal incident of the laser beam, and is formulated from Rayleigh’s diffraction conditions as Λ = λ/[n0(1±sinθ i)] , (1) for a p-polarized beam, where n0 is the refractive index of the incident medium above the surface. The periodic pattern has alternating peaks and valleys forming parallel lines. The direction of the stripe is perpendicular to the electric field vector (E) of the incident beam. In our previous work, we deposited a 60-nm-thick amorphous Si (a-Si) film on a glass substrate and irradiated a linearly polarized laser beam, and obtained LIPSS on the surface of a polycrystalline Si (poly-Si) film according to the periodic energy density distribution (periodic E-D) [1], as shown in Fig. 1(a) schematically. An increased periodic surface roughness with increasing pulse number leads to an increase in diffracted beam intensity, which leads to an increase in the amplitude of periodic E-D. Moreover, we deposited a very thin a-Si film of about 10 nm and irradiated the laser beam, and the molten Si film split and condensed according to the periodic E-D. Then, we could obtain a periodically aligned submicron Si lines (line and space structure) [2], as shown in Fig. 1(b). In this study, we applied a spontaneously induced periodic E-D to the fabrication of peri
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