Tailoring the functionalities of MoS₂ field-effect transistors by an area-selective surface charge transfer doping strategy

Surface charge transfer doping (SCTD) is widely recognized as an effective and non-destructive method for modulating the electrical properties of atomically thin transition metal dichalcogenides (TMDs), capitalizing on their distinctive two-dimensional (2D) structure. Nevertheless, the challenges of achieving precise area-selective doping using conventional methods, such as dopant vaporization, have impeded the advancement of practical optoelectronic and electronic devices based on TMDs. Herein, we propose a simple and reliable area-selective SCTD strategy to facilitate transfer, doping, and encapsulation simultaneously during the polyvinyl alcohol (PVA)-assistant transfer process. The electrical performance of PVA-doped molybdenum disulfide (MoS₂) field-effect transistor (FET) exhibited significant enhancement, with carrier concentrations reaching up to 10¹³ cm⁻², on-state currents increasing to 10 μA·μm⁻¹, and on/off ratios attaining a remarkable value of 10⁷. Optical photothermal infrared (O-PTIR) spectroscopy was employed to elaborate the intrinsic temperature-dependent doping mechanism. The functionalization of MoS₂ FETs was successfully achieved by introducing a hexagonal boron nitride (hBN) capping layer to define the doping area, enabling the creation of a homojunction with a rectification ratio of 10⁶, an inverter fabricated within a single channel, and a Schottky barrier as low as 30.17 meV at the Au/MoS₂ interface. This area-selective SCTD strategy, enabled by the PVA-assisted transfer process, offers a reliable, efficient, and economical approach for tailoring the functionalities of TMD-based devices, demonstrating substantial potential for diverse electronic applications.