Work Function Modulation of Molybdenum Disulfide Nanosheets by Introducing Systematic Lattice Strain.

Tuning the surface electronic properties of 2D transition metal dichalcogenides such as Molebdenum disulfide (MoS) nanosheets is worth exploring for their potential applications in strain sensitive flexible electronic devices. Here in, the correlation between tensile strain developed in MoS nanosheets during swift heavy ion irradiation and corresponding modifications in their surface electronic properties is investigated. With prior structural characterization by transmission electron microscopy, chemically exfoliated MoS nanosheets were exposed to 100 MeV Ag ion irradiation at varying fluence for creation of controlled defects. The presence of defect induced systematic tensile strain was verified by Raman spectroscopy and X-ray Diffraction analysis. The effect of ion irradiation on in-plane mode is observed to be significantly higher than that on out-of-plane mode. The contribution of irradiation induced in-plane strain on modification of the surface electronic properties of nanosheets was analyzed by work function measurement using scanning Kelvin probe microscopy. The work function value is observed to be linearly proportional to tensile strain along the basal plane indicating a systematic shifting of Fermi surface with fluence towards the valence band.