Theoretical Analysis of Fano Resonance in Niobium Selenide and Titanium Carbide Heterojunction for Ultrahigh FOM in Biorefractive Index Detection

Transition metal diselenides (TMSes), as a new class of 2-D semiconductor materials, have higher thermal stability, stronger optoelectronic properties, and higher carrier mobility than sulfides and perform better in optoelectronic devices. Among them, 2-D niobium diselenide (NbSe2) nanocrystals have excellent flexibility, fast optical response properties, outstanding chemical stability, and light absorption properties and thus have potential applications in the field of optical sensors. Here, we present for the first time an optical biosensor based on multilayer NbSe2, which can achieve high sensitivity and high figure of merit (FOM) response to the refractive index of the medium by precise tuning of the optical and structural parameters of the sensor. The results of the theoretical study show that the multilayer NbSe2 at the nanoscale is capable of producing extremely strong Fano resonance effects in the proposed sensor structure in this article. Compared with the conventional Au thin-film surface plasmon resonance (SPR)-based sensor, the FOM of the NbSe2 at Ti3C2-MXene Fano-SPR-based sensor proposed in this study is substantially improved by a factor of 28. Our theoretical study demonstrates that NbSe2 is a surface plasmonic material with excellent Fano effect, which provides a theoretical reference for its experimental study in the field of biosensors.