Bipolar Doping in van der Waals Semiconductors through Flexo-Doping.

Doping plays a key role in functionalizing semiconductor devices, yet traditional chemical approaches relying on foreign-atom incorporation suffer from doping asymmetry, pronounced lattice disorder, and constrained spatial resolution. Here, we demonstrate a physical doping technique to directly write nanoscale doping patterns into layered semiconductors (MoS2). By applying localized tensile and compressive stress via an atomic force microscopy probe, p-type and n-type conductances are simultaneously written into the designed area with sub-100 nm resolution, as verified by spatially resolved capacitance and photocurrent experiments. Density functional theory calculations reveal strain-driven shifts of donor and acceptor levels as large as several hundreds of meV, linking mechanical stress to semiconductor doping. The fabricated strain-engineered junction efficiently rectifies the current flow and performs logic operations with a stable dynamic response. This strain-driven approach enables spatially precise doping in van der Waals materials without degrading crystallinity, offering a versatile platform for nanoscale semiconductor devices.