Design and Simulation of SPR Sensors by Employing Silicon and Silicon-Nitride With Mono and Bimetal Layers for Sensitivity Enhancement

In this work, three novel surface plasmon resonance (SPR) sensors based on the Kretschmann configuration are proposed. The optimized structural designs of Sensor 1 [BK7/Si (42 nm)/Au (25 nm)/Ag (25 nm)/Si3N4 (18 nm)/sensing medium] and Sensor 2 [BK7/Si (10 nm)/Au (30 nm)/Ag (30 nm)/Si3N4 (20 nm)/sensing medium] incorporate bimetallic layers of gold (Au) and silver (Ag), while Sensor 3 [BK7/Si (32 nm)/Ag (25 nm)/Si3N4 (20 nm)/sensing medium] includes only an Ag layer. These biosensors feature silicon (Si) and silicon nitride (Si3N4) as dielectric layers. The study uses the transfer matrix method to optimize the sensors and evaluates their performance using the angle modulation method. Results indicate that reverse optimization, optimizing the Si3N4 layer before the Si layer, yields significantly better performance than conventional optimization. Sensor 2 outperforms Sensor 1 and Sensor 3, demonstrating superior sensitivity, detection accuracy (DA), and figure of merit (FoM). The maximum sensitivity ( ${S}$ ), DA, and FoM for Sensor 1 are calculated as 440°/RIU, 0.1470 1/degree, and 64.70 1/RIU, respectively. Sensors 2 and Sensor 3 achieve even higher performance when analyzed using reverse optimization, with their sensitivity ( ${S}$ ), DA, and FoM values at 460°/RIU, 0.2222 1/degree, 102.222 1/RIU, and 460°/RIU, 0.2197 1/degree, 101.09 1/RIU, respectively. These novel SPR sensors demonstrate exceptional performance, as substantiated by a thorough comparison to the recently published works in the field of biomedical applications. This comparison underscores the sensors' considerable potential in biosensing and biomedicine.