Measurements of Sensitivity and Figure of Merit for Noble Metals (Au, Ag, Cu) Thin Film Biosensor Based on SPR Simulation Characterizations

In this paper, we investigate the influence of varying the thickness of noble metals, namely gold (Au), silver (Ag) and copper (Cu), and the incident light wavelength on the surface plasmon resonance (SPR) properties for biosensor applications. Our analysis employs the Fresnel equations to examine the absorption characteristics of these metals when the refractive index shifts by (0.03,0.06). We explore metal layer thicknesses ranging from d=30to70nm and incident light wavelengths of lambda=500 and 600nm, with incident angles (theta) ranging from 0 degrees to 90 degrees. Utilizing simulation analysis in MATLAB, we simulate the SPR responses of these metals when deposited on BK-7 glass prisms, with air as the surrounding medium. Our calculations reveal the absorption properties of Au, Ag and Cu, as indicated by the angle of incidence (theta SPR). Our findings demonstrate that the highest absorption occurs with copper (Cu) at A=0.999 (a.u.) for lambda=500nm and d=30nm. When lambda is adjusted to 600nm, gold (Au) exhibits the highest absorption (A) at 0.997 (a.u.) with a thickness of d=40nm. Additionally, we calculate sensitivity values for all three metals, with copper (Cu) yielding the highest sensitivity of 101.6 Reflected Index Units (RIU-1) for both lambda=500 and 600nm. Furthermore, we compute the Figure Of Merit (FOM), with silver (Ag) achieving the highest FOM of 443 at lambda=500nm and 451 at lambda=600nm. These results provide important signs about noble metals' SPR properties in biosensing, and serve as guides for optimizing the biosensors.