Periodic Alignment of Silicon Dot Fabricated by Linearly Polarized Nd:YAG Pulse Laser
- PDF / 1,138,302 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 85 Downloads / 164 Views
0910-A15-03
Periodic Alignment of Silicon Dot Fabricated by Linearly Polarized Nd:YAG Pulse Laser Kensuke Nishioka, and Susumu Horita Graduate School of Materials Science, Japan Advanced Institute of Science and Technology, Nomi, Ishikawa, 923-1292, Japan
ABSTRACT Periodically aligned submicron Si dots were fabricated by only irradiating linearly polarized Nd:YAG pulse laser to the amorphous silicon (a-Si) thin film deposited on silicon dioxide (SiO2) film. Interference between the incident beam and the scattered surface wave leads to the spatial periodicity of beam energy density distribution on the surface of the irradiated samples. The a-Si thin film was melted by laser beam, and then, the molten thin Si film was split and condensed due to its surface tensile according to the periodic energy density distribution. The polycrystalline Si (poly-Si) fine lines were formed periodically. After the first irradiation, the sample was rotated by 90o, and the laser beam was irradiated. The periodic energy density distribution was generated on the Si fine lines. Then, the lines were split off and condensed according to the periodic energy density distribution, and the periodically aligned submicron Si dots were fabricated on the SiO2 film. INTRODUCTION Recently, submicron or nano-structures have been used for fluidic, electronic, optic, and mechanical devices in various fields. Most of those fine structures are fabricated by conventional lithographic process, and they require complicated steps including masking and molding. Therefore, there is much demand for fabrication techniques of fine structures without lithographic process for faster and cheaper manufacturing. It has been reported that linearly polarized laser irradiation induces spatially periodic structures on the surfaces of semiconductor [1-4], metal [5-7], and polymer [8,9]. This means that the laser irradiation produces a periodic temperature distribution on the surface. For most of the case, the periodic spacing Λ of the energy density distribution on the surface depends on the wavelength λ and the incident angle from the normal incident θ of the laser beam, and is formulated from Rayleigh’s diffraction conditions as
Λ = λ/[n0(1±sinθ)] ,
(1)
for 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 of the incident beam. In this study, we applied the spontaneously induced periodic energy density distribution to fabrication of periodically aligned submicron Si dots.
EXPERIMENT A 50-nm-thick oxide layer was grown by the thermal oxidization of a silicon wafer. Then, a 10-nm-thick amorphous Si (a-Si) film was deposited on the thermal oxidized Si substrate at 350oC by electron beam evaporation in a ultrahigh vacuum chamber (base pressure: 1x10-10 Torr), and was irradiated by linearly polarized Nd:YAG pulse laser beam (λ: 532 nm, Repetition frequency: 10 Hz, Pulse width: 6-
Data Loading...
