Controllable Doping of Transition-Metal Dichalcogenides by Organic Solvents

Seeking controllable and efficient surface dopant molecules for transition-metal dichalcogenides (TMDCs) is highly valuable for fully understanding TMDCs properties and their applications to relevant devices. The general doping effect of solvents on TMDCs are explored. By selecting suitable solvents with optimized relevant factors, controllable n-doping of molybdenum disulfide (MoS2) is obtained on the same device with the sheet density of electrons increased from 2.3 x 10(11) to 6.4 x 10(12), 9.7 x 10(12), and 1.6 x 10(13) by use of dimethylsulfoxide, N,N-dimethylformamide, and N-methyl-pyrrolidone (NMP), respectively. The doping principle is explained by charge-donating characteristics of molecule and dipole interaction. After doping by NMP, the contact resistance is reduced by four times, and the on/off current ratio of fabricated top-gated MoS2 transistors is increased by 3 orders of magnitude. This work can guide the selection of suitable solvents for effective doping of two-dimensional materials and advance the development of precise controllable electronic and optoelectronic devices.