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.

Two-/three-dimensional (2D/3D) heterojunction-based photodetectors have attracted much attention due to their highly efficient photoelectric conversion driven by the built-in electric field for high-speed photoresponse. However, a large dark current induced by unexpected surface states at the interface between 2D materials and 3D bulks is widely observed in such structures, greatly degrading their optoelectronic performance. Herein, a heterojunction of proton acid HCl treated MXene (H-MXene)/TiO₂/Si via integrating surface and interface engineering is fabricated, which exhibits decreased dark current and improved environmental stability. A feasible strategy to optimize the interface properties between MXene and Si is proposed by an in-situ oxidation process of MXene into TiO₂, resulting in a suppressed dark current as well as high specific detectivity. Benefitting from the enhanced light absorption of MXene on the bulk Si substrate, the photoresponse of as-fabricated devices in the near-infrared region is also elevated. Moreover, the treatment of proton acid HCl on the surface of MXene brings better conductivity and environmental stability due to the decreased layer spacing of MXene, which is further confirmed by both experimental and theoretical methods. This work opens a unique way to comprehensively boost the optoelectronic performance of MXene-based photodetectors.