The effect of air stable n-doping through mild plasma on the mechanical property of WSe layers.

Two-dimensional transition metal dichalcogenides have been widely applied to electronic and optoelectronic device owing to their remarkable material properties. Many studies present the platform for regulating the contact resistance via various doping schemes. Here, we report the alteration of mechanical properties of few top layers of the WSe flake which are processed by air stable n-doping of NO with a constant gas flow through mild plasma and present better manufacturability and friability. The single-line nanoscratching experiments on the WSe flakes with different doping time reveal that the manufacturable depths are positively correlated with the exposure time at a certain range and tend to be stable afterwards. Meanwhile, material characterization by x-ray photoelectron spectroscopy confirms that the alteration of mechanical properties is owing to the creation of Se vacancies and substitution of O atoms, which breaks the primary molecular structure of the WSe flakes. The synchronous Kelvin probe force microscopy and topography results of ROI nanoscratching of a stepped WSe sample confirmed that the depth of the degenerate doping is five layers, which was consistent with the single-line scratching experiments. Our results reveal the interrelationship of the mechanical property, chemical bonds and work function changes of the doped WSe flakes.