Nanoscale Control of Carrier Transport in Monolayer Transition-Metal Dichalcogenide Double Heterostructures

Heterostructures are fundamental to modern electronics and optoelectronics. Lateral heterostructures of two-dimensional (2D) semiconductors provide a promising platform for monolayer device architecture. However, the carrier transport mechanisms across these lateral heterointerfaces, especially in heterostructures with nanometer-scale dimensions, remain underexplored. Here, we report the synthesis of monolayer transition-metal dichalcogenide lateral double heterostructures (LDHs) with coherent, dislocation-free interfaces and sub-10 nm dimensional control, including WS₂-MoS₂-WS₂ and WS₂-WSe₂-WS₂. Using WS₂-WSe₂-WS₂ LDHs as a model system, we investigate the electron transport mechanism across the WSe₂ barrier and observe a transition from thermionic emission to direct tunneling as the WSe₂ width decreases to sub-10 nm. Importantly, the effective barrier height can be modulated by the gate voltage and source-drain bias, enabling electrostatic control of charge injections. These findings establish LDHs as a powerful platform for engineering transport within monolayer semiconductors, offering new opportunities for next-generation 2D electronic and quantum devices.