主催: The Japan Society of Vacuum and Surface Science
会議名: 2023年日本表面真空学会学術講演会
開催地: 名古屋
開催日: 2023/10/31 - 2023/11/02
Molecules show strong infrared absorption when adsorbed on metal nanoparticles or on the surface of discontinuous metal thin films. The phenomenon was reported first by Hartstein et al. in 1980 [1] and is known as surface-enhanced infrared absorption (SEIRA). SEIRA has been used in various fields, such as the detection of trace chemical species and the tracking of chemical reactions on electrode surfaces [2]. Our previous study suggested that SEIRA occurs not only on metal nanostructured surfaces but also on non-metal nanostructured surfaces [3]. Therefore, we conducted infrared absorption spectroscopy measurements on line and space nanostructured surfaces of silicon, a semiconductor material.
The line and space nanostructures were fabricated in the Takeda–Sentanchi Building's super clean room at the University of Tokyo. Each structure occupies 1600 × 1600 μm2 on a silicon substrate. The line width of the line and space structure was 100 nm, with four different line periods of 350 nm, 600 m, 850 nm, and 1100 nm. Polyacrylic acid (PAA; Wako Pure Chemical Industries Ltd.) was spin-coated onto the substrate with the line and space nanostructures. A 200 μL droplet of 1 to 10 g L-1 PAA ethanol solution was dropped on the substrate. The infrared absorption spectroscopy was performed by p-polarized multi-angle incidence resolved spectroscopy (pMAIRS).
The enhancement factors of infrared absorption for the line and space nanostructures were found to be three to four. Comparing the enhancement factor of the peaks around 902 cm-1 and 1710 cm-1, the peak around 902 cm-1 was more enhanced. Longer line periods give a greater enhancement factor. However, when the line period is more than about one-tenth of the excitation wavelength, the enhancement effect is smaller.
References
[1] A. Hartstein, J.R. Kirtley, J.C. Tsang, Phys. Rev. Lett. 45, 201 (1980).
[2] M. Osawa, Appl. Phys. 81, 163 (2001).
[3] T. Shimada, H. Nagashima, Y. Kumagai, Y. Ishigo, M. Tsushima, A. Ikari, Y. Suzuki, J. Phys. Chem. C 120, 534 (2016).
