Formation of Silicon and Silicon-Based Semiconductor Materials via Photoinduced Reaction Using Femtosecond Laser
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Formation of Silicon and Silicon-Based Semiconductor Materials via Photoinduced Reaction Using Femtosecond Laser Masakazu Nishimura1, Shingo Kanehira2, Masaaki Sakakura2, Yasuhiko Shimotsuma2, Kiyotaka Miura1 and Kazuyuki Hirao1 1
Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Japan
2
Society-Academia Collaboration for Innovation, Kyoto University, Japan
ABSTRACT We have succeeded in silicon (Si) precipitation inside a glass/aluminum (Al) sandwich structure via photoinduced reaction using femtosecond (fs) laser irradiation. The sandwich structure was fabricated by direct bonding below 573 K. Raman spectra at the photomodified area indicated that Si crystals formed at the interface between the glass and metallic Al after the laser irradiation. In addition, the particle size of the precipitated Si could be changed by changing the pulse energy of the laser. Furthermore, we have also focused the laser pulses on Fe-Si film to trigger crystallization and phase transformation of FexSiy at the interface between Fe/Si multilayer and glass.
INTRODUCTION Femtosecond (fs) lasers have been widely used in microfabrication of various materials because of their ability to suppress thermal damages of the materials near the focus. In the case of fabricating three-dimensional microstructures inside transparent materials, it is possible to induce a refractive index change only near the focal point of the laser inside the materials due to a multiphoton absorption. There have been many reports on various microstructures using fs laser irradiation; waveguides [1,2], voids [3,4], optical memory [5], and localized crystallization [6]. As described above, fs laser is a promising tool to miniaturize various devices such as photonic, electronic devices and so on. Si is one of the important photonic materials because of its optical properties, such as high refractive index (n=3.5) and transparency at infrared wavelength. It is possible for Si to be utilized as waveguides with low propagation losses and small bending radius. However, it is necessary to control a site-selective precipitation of Si inside a glass which has a low refractive index. It has been previously reported that Si was precipitated at the interface between Al and SiO2 via thermal annealing above 773 K [7]. The formation of an oxygen-deficiency inside a silica glass [8] or Si nanoparticles in Al-doped silicate glass [9] were also demonstrated by using fs laser. It is important to investigate in detail the mechanism of Si precipitation at the interface between a glass and Al after laser irradiation.
In this paper, we demonstrated Si deposition at the interface Al/SiO2-based glass using fs laser. Firstly, a metallic film was inserted between two glass substrates by a bonding technique without adhesive agents in order to avoid an ablation of the film in the laser irradiation. Next, the Si precipitation was demonstrated by fs laser irradiation. Furthermore, we tried to apply this technique to a photoinduced reaction in Fe-Si binary system
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