A High-Sensitivity Sensor Based on Insulator-Metal-Insulator Structure.

In this paper, a theoretical model of a surface plasmon resonance (SPR) biosensor based on the insulator-metal-insulator (IMI) structure is proposed. The sensor mainly consists of two IMI structures, MgF₂/Au/Al₂O₃ and Al₂O₃/Au/sensing medium structure, respectively. Benefits from the symmetrical modes stimulated by the IMI structure, i.e., the electric field strength inside the sensing medium, are reinforced, resulting in a better overall performance in sensitivity and figure of merit (FOM). The influences of the thickness of the metal layers, the parameters of the dielectric layer materials, and the number of structural layers on the performance of this sensor are discussed. When the refractive index (RI) of the analyte varies in the range of 1.3494–1.3495, the optimized sensor could achieve a maximum wavelength sensitivity of 220 μm/RIU (refractive index unit) and a FOM of 3013.70 RIU⁻¹. Compared with the conventional SPR sensor, the sensitivity and FOM of this structure are significantly improved. [ABSTRACT FROM AUTHOR]