Low-Frequency Noise in Layered ReS

Layered rhenium disulfide (ReS2) field effect transistors (FETs), with thickness ranging from few to dozens of layers, are demonstrated on 20 nm thick HfO2/Si substrates. A small threshold voltage of -0.25 V, high on/off current ratio of up to ∼107, small subthreshold swing of 116 mV/dec, and electron carrier mobility of 6.02 cm2/V·s are obtained for the two-layer ReS2 FETs. Low-frequency noise characteristics in ReS2 FETs are analyzed for the first time, and it is found that the carrier number fluctuation mechanism well describes the flicker (1/f) noise of ReS2 FETs with different thicknesses. pH sensing using a two-layer ReS2 FET with HfO2 as a sensing oxide is then demonstrated with a voltage sensitivity of 54.8 mV/pH and a current sensitivity of 126. The noise characteristics of the ReS2 FET-based pH sensors are also examined, and a corresponding detection limit of 0.0132 pH is obtained. Our studies suggest the high potential of ReS2 for future low-power nanoelectronics and biosensor applications.