Two different device physics principles for operating MoS2 transistor biosensors with femtomolar-level detection limits

We experimentally identify two different physics principles for operating MoS2 transistor biosensors, which depend on antibody functionalization locations. If antibodies are functionalized on an insulating layer coated on a MoS2 transistor, antibody-antigen binding events mainly modify the transistor threshold voltage, which can be explained by the conventional capacitor model. If antibodies are directly grafted on the MoS2 transistor channel, the binding events mainly modulate the ON-state transconductance of the transistor, which is attributed to the antigen-induced disordered potential in the MoS2 channel. This work advances the device physics for simplifying the transistor biosensor structures targeting for femtomolar-level quantification of biomolecules.