Role of Interfacial States in the Molecular Interaction in Electro-Optically Doped Two-Dimensional MoS₂

The energy states in semiconductor devices are mainly tuned by the gate field, which is limited by the material characteristics. The novel field effect transistor (FET) device is fabricated by coupling a two-dimensional monolayer of molybdenum disulfide (MoS 2 ) with the metal plasmonic structure of dimers. The collective oscillation of electrons within each dimer induces a strong coupling with MoS 2 (plasmonic-MoS 2 ) through charge transfer at the interface. Thus, the turn-on voltage of the meta-FET device results in a significant shift of 483% to a higher negative potential upon optical interaction. An electro-optically sensitive metasurface was exposed to the molecules of opposite polarity like ammonia (NH 3 ) and sulfur dioxide (SO 2 ). Both the A-exciton and B-exciton in plasmonic MoS 2 demonstrated excellent sensitivity to the polarity of molecules due to the electro-optical doping of MoS 2 . Transfer characteristics of the meta-FET device showed an excellent variation of 518% and 2506% in the maximum drain current upon interaction with NH 3 and SO 2 molecules in the presence of optical excitations. Density functional calculations revealed that upon light interactions, the trapped charges can be released in larger amounts, resulting in more charge transfer to MoS 2 from the Au interface, thereby improving the charge sensing capabilities of the surface. The meta-FET device provides a novel paradigm for electronic devices by 2-fold doping to overcome limitations of material properties.