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.

This study proposes a feasible and scalable production strategy to naturally obtain aligned platinum diselenide (PtSe₂) nanoribbon arrays with anisotropic conductivity. The anisotropic properties of two-dimensional (2D) materials, especially transition-metal dichalcogenides (TMDs), have attracted great interest in research. The dependence of physical properties on their lattice orientations is of particular interest because of its potential in diverse applications, such as nanoelectronics and optoelectronics. One-dimensional (1D) nanostructures facilitate many feasible production strategies for shaping 2D materials into unidirectional 1D nanostructures, providing methods to investigate the anisotropic properties of 2D materials based on their lattice orientations and dimensionality. The natural alignment of zigzag (ZZ) PtSe₂ nanoribbons is experimentally demonstrated using angle-resolved polarized Raman spectroscopy (ARPRS), and the selective growth mechanism is further theoretically revealed by comparing edges and edge energies of different orientations using the density functional theory (DFT). Back-gate field-effect transistors (FETs) are also constructed of unidirectional PtSe₂ nanoribbons to investigate their anisotropic electrical properties, which align with the results of the projected density of states (DOS) calculations. This work provides new insight into the anisotropic properties of 2D materials and a feasible investigation strategy from experimental and theoretical perspectives.