Strained 2D TMD lateral heterojunctions via grayscale thermal-Scanning Probe Lithography

Abstract: Nanoscale tailoring of the optoelectronic response of 2D Transition Metal Dichalcogenides semiconductor layers (TMDs) has been achieved thanks to a novel strain engineering approach based on the grayscale thermal-Scanning Probe Lithography (t-SPL). This method allows the maskless nanofabrication of locally strained 2D MoS2-Au lateral heterojunction nanoarrays that are characterized by asymmetric electrical behavior. 2D MoS2 layers are conformally transferred onto grayscale t-SPL templates characterized by periodic nanoarrays of deterministic faceted nanoridges. This peculiar morphology induces asymmetric and uniaxial strain accumulation in the 2D TMD material allowing to tailor their electrical work-function at the nanoscale level, as demonstrated by Kelvin Probe Force Microscopy (KPFM). The modulation of the electronic response has been exploited to develop periodic nanoarrays of lateral heterojunctions endowed with asymmetric electrical response by simple maskless deposition of Au nanocontacts onto the strained 2D TMD layers. The locally strained Au-MoS2 layers show asymmetric lateral heterojunctions with engineered carrier extraction functionalities, thus representing a promising platform in view of tunable ultrathin nanoelectronic, nanophotonic and sensing applications.