Hole doping effect of MoS via electron capture of He ion irradiation.

Beyond the general purpose of noble gas ion sputtering, which is to achieve functional defect engineering of two-dimensional (2D) materials, we herein report another positive effect of low-energy (100 eV) He ion irradiation: converting n-type MoS to p-type by electron capture through the migration of the topmost S atoms. The electron capture ability via He ion irradiation is valid for supported bilayer MoS; however, it is limited at supported monolayer MoS because the charges on the underlying substrates transfer into the monolayer under the current condition for He ion irradiation. Our technique provides a stable and universal method for converting n-type 2D transition metal dichalcogenides (TMDs) into p-type semiconductors in a controlled fashion using low-energy He ion irradiation.