Abstract

Surface plasmon resonances (SPR) when combined with spectroscopy technique is a powerful method for monitoring dynamic biological interactions under label-free and nondestructive detection [1]. Molecular signals can be largely enhanced through the coupling between the molecular vibrations and SPRs in mid-IR spectral range, which is the basic principle of molecule recognitions. Highly doped semiconductors with higher FoMs have been developed by our team as plasmonic materials for biosensing platforms [2-3]. In this research, we prepared ZnO: Ga microdot arrays with different periods (Diameter (D): 4 μm and Spacing (L): 2 ~ 9 μm) on CaF₂ substrates by photo-lithography and pulsed laser deposition, employing surface lattice resonances (SLRs) to couple to SPRs. To demonstrate the effect of substrate-induced screening filed on the plasmon oscillations in microdots, we deposited ZnO: Ga arrays on substrates with different refractive indices (RI). Reflectance spectra of p-pol. and s-pol. light under changing incident angles were measured by ellipsometry and the origins of the peaks were confirmed through theoretical calculations. On the surface of the ZnO: Ga microdot arrays, we aim to detect DNA molecules with phosphate related vibrational absorptions at around 1000 cm^-1.

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