研究目的
To improve the signal-to-noise ratio in the observation of Raman light scattering from molecular compounds by investigating periodically profiled metasurfaces of silicon and silver-coated silicon.
研究成果
The metasurface provides a high RS-to-luminescence signal ratio, making it an efficient SERS substrate. The RS signal from DTNB molecules is significantly enhanced due to electromagnetic enhancement of the local optical field, with resonances tunable by varying structural parameters and light incidence angle.
研究不足
The optical loss in silicon increases with decreasing wavelength, limiting effectiveness to wavelengths longer than ~550 nm. There is significant inaccuracy in measured data for silver-coated samples, and nonuniform surface adsorption of the analyte remains unsolved.
1：Experimental Design and Method Selection:
The study involves experimental investigation and computer simulation of metasurfaces to enhance local electromagnetic fields. Finite element method in COMSOL is used for numerical calculations.
2：Sample Selection and Data Sources:
Silicon metasurfaces with and without a thin silver layer are prepared using high-resolution electron-beam lithography and ion etching. DTNB molecules are used as indicators for SERS.
3：List of Experimental Equipment and Materials:
Equipment includes Crestec CABL 9000C machine for electron-beam lithography, CORIAL 200I etch tool for ion etching, WiTec spectrometer for Raman spectroscopy, and COMSOL software for simulations. Materials include silicon substrates, silver for coating, and DTNB molecules.
4：Experimental Procedures and Operational Workflow:
Metasurfaces are fabricated, coated with silver, and characterized using reflection measurements and Raman spectroscopy. Laser radiation at 785 nm is used for excitation, with measurements taken for different polarizations and incidence angles.
5：Data Analysis Methods:
Spectral dependences of reflection coefficients are analyzed, and Raman signal intensities are compared between different surface types and polarizations.
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