Strained 2D Semiconductor Lateral Heterojunctions via Grayscale Thermal-Scanning Probe Lithography

Nanoscale tailoring of the optoelectronic response of 2D transition metal dichalcogenides semiconductor layers (TMD) is demonstrated thanks to a novel strain engineering approach based on 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 lateral modulation of the electronic band structure. 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 us to tailor their electrical work-function at the nanoscale level, as demonstrated by Kelvin Probe Force Microscopy. By tailoring the local morphology of the grayscale nanopatterns, the capability to control the strain-dependent electrical work function of the 2D TMD layers at the local scale is demonstrated. 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 form asymmetric lateral heterojunctions with strain-modulated Schottky versus Ohmic behavior, thus representing a promising platform in view of tunable ultrathin nanoelectronics, nanophotonic, and sensing applications.