Two-dimensional plumbum-doped tin diselenide monolayer transistor with high on/off ratio

Doping can effectively regulate the electrical and optical properties of two-dimensional semiconductors. Here, we present high-quality Pb-doped SnSe₂ monolayer exfoliated using a micromechanical cleavage method. X-ray photoelectron spectroscopy measurement demonstrates that Pb content of the doped sample is ∼3.6% and doping induces the downward shift of the Fermi level with respect to the pure SnSe₂. Transmission electron microscopy characterization exhibits that Pb_0.036Sn_0.964Se₂ nanosheets have a high-quality hexagonal symmetry structure and Pb element is uniformly distributed in the nanosheets. The current of the SnSe₂ field effect transistors (FETs) was found to be very difficult to turn off due to the high electron density. The FETs based on the Pb_0.036Sn_0.964Se₂ monolayer show n-type behavior with a high on/off ratio of 10⁶ which is higher than any values of SnSe₂ FETs reported at the moment. The estimated carrier concentration of Pb_0.036Sn_0.964Se₂ is approximately six times lower than that of SnSe₂. The results suggest that the method of reducing carrier concentration by doping to achieve high on/off ratio is effective, and Pb-doped SnSe₂ monolayer has significant potential in future nanoelectronic and optoelectronic applications.