Field-effect transistor with a chemically synthesized MoS2 sensing channel for label-free and highly sensitive electrical detection of DNA hybridization

A field-effect transistor (FET) with two-dimensional (2D) few-layer MoS2 as a sensing-channel material was investigated for label-free electrical detection of the hybridization of deoxyribonucleic acid (DNA) molecules. The high-quality MoS2-channel pattern was selectively formedthrough the chemical reaction of the Mo layer with H2S gas. The MoS2 FET was very stable in an electrolyte and inert to pH changes due to the lack of oxygen-containing functionalities on the MoS2 surface. Hybridization of single-stranded target DNA molecules with single-stranded probe DNA molecules physically adsorbed on the MoS2 channel resulted in a shift of the threshold voltage (Vth) in the negative direction and an increase in the drain current. The negative shift in Vth is attributed to electrostatic gating effects induced by the detachment of negatively charged probe DNA molecules from the channel surface after hybridization. A detection limit of 10 fM, high sensitivity of 17 mV/dec, and high dynamic range of 106 were achieved. The results showed that a bio-FET with an ultrathin 2D MoS2 channel can be used to detect very small concentrations of target DNA molecules specifically hybridized with the probe DNA molecules.