Interfacial Doping Effects in Fluoropolymer-Tungsten Diselenide Composites Providing High-Performance P-Type Transistors.

In this study, we investigated the p-doping effects of a fluoropolymer, Cytop, on tungsten diselenides (WSe2). The hole current of the Cytop-WSe2 field-effect transistor (FET) was boosted by the C-F bonds of Cytop having a strong dipole moment, enabling increased hole accumulation. Analysis of the observed p-doping effects using atomic force microscopy (AFM) and Raman spectroscopy shed light on the doping mechanism. Moreover, Cytop reduces the electrical instability by preventing the adsorption of ambient molecules on the WSe2 surface. Annealing Cytop deposited on WSe2 eliminated the possible impurities associated with adsorbates (i.e., moisture and oxygen) that act as traps on the surface of WSe2. After thermal annealing, the Cytop-WSe2 FET afforded higher p-type conductivity and reduced hysteresis. The combination of the Cytop-WSe2 FET with annealing provides a promising method for obtaining high-performance WSe2 p-type transistors.