Wei Luo

Twisted bilayer transition metal dichalcogenides (TB-TMDs) have emerged as a versatile platform for fabricating moiré superlattices and exploring correlated electronic behavior, particularly in revealing the interplay between exciton dynamics and twisted angles. However, the direct synthesis of high-quality TB-TMDs nanosheets has been hindered by thermodynamic instability. Here, we develop an oxygen-assisted physical vapor deposition strategy to directly synthesize TB-MoS₂ nanosheets with twist-angle-dependent exciton dynamics. First-principles calculations reveal that oxygen incorporation significantly reduces the formation energy of TB-MoS₂. Guided by this analysis, an oxygen-modulated precursor system is successfully designed to synthesize high-quality TB-MoS₂ nanosheets with well-defined moiré patterns and a broad angular distribution. Besides, for A exciton, it is demonstrated that the time constant t₂ corresponding to the radiative recombination process is shorter at the twist angles of 0° and 60° compared to 12°, 24°, 40°, and 47°. This result is attributed to reduced interlayer distance and enhanced interlayer coupling, as supported by differential charge density and density of states calculations. Furthermore, t₂ is shorter at 24° and 40° than at 12° and 47°, owing to a smaller energy difference between indirect and direct bandgaps. Our work not only establishes an effective route for fabricating TB-TMDs but also deepens the understanding of twist-angle-engineered moiré photonics.

Dimensionality and morphology critically tailor material properties by controlling electron behavior through modifications to crystal symmetry and potential fields. However, precise dimensionality control in low‐dimensional materials remains challenging. The controlled synthesis of 2D and 1D Fe _1+y Te nanocrystals (y < 0.12) with distinct electromagnetic transport properties via chemical vapor deposition (CVD) is demonstrated. By reducing the distance between the Fe and Te sources, the morphology of Fe _1+y Te nanocrystals evolves from 2D quasi‐square and ribbon‐shaped structures to 1D nanoribbons. Spherical aberration‐corrected scanning transmission electron microscopy (STEM) analysis reveals that this dimensional transition is likely driven by intermediate phases with anisotropic formation energy. Electromagnetic transport measurements indicate that both 2D and 1D Fe _1+y Te nanocrystals undergo a structural phase transition from tetragonal to monoclinic symmetry, accompanied by a magnetic phase transition from paramagnetic to bicollinear antiferromagnetic states upon cooling. unlike the metallic behavior of 2D Fe _1+y Te, the 1D nanoribbons exhibit field‐induced semiconducting characteristics. Moreover, a charge density wave (CDW) state emerges near 22 K exclusively in the 1D nanoribbons. These findings establishes a versatile platform for dimension‐controlled fabrication of low‐dimensional materials and exploration of their emergent physical phenomena.

Reconfigurable two-dimensional (2D) devices have garnered significant attention for next-generation electronics due to their adaptive functionality and structural advantages, yet achieving nondestructive, programmable reconfiguration in simple 2D transistors remains challenging. We introduce a gate-controlled graded ozone (O₃) strategy to dynamically reconfigure palladium diselenide (PdSe₂) devices. Systematic characterization confirms the nondestructive nature of O₃ adsorption while enabling controllable hole doping via surface charge transfer modulation. This graded doping profile facilitates programmable logic inverters and artificial synapses. Our PdSe₂-based complementary inverters achieve ultralow voltage operation at 0.05 V, while the artificial synapses exhibit metaplasticity at an ultralow energy consumption of 0.35 fJ per synaptic event. This O₃-mediated reconfiguration approach offers a versatile platform for multifunctional 2D electronics and adaptive neuromorphic computing.

Two-dimensional (2D) ferroelectrics usually exhibit instability or a tendency toward degradation when exposed to the ambient atmosphere, and the mechanism behind this phenomenon remains unclear. To unravel this affection mechanism, we have undertaken an investigation utilizing NH₃ and two-dimensional ferroelectric SnS. Herein, the adsorption and desorption of NH₃ molecules can reversibly modulate the electrical properties of SnS, encompassing I–V curves and transfer curves. The response time for NH₃ adsorption is approximately 1.12 s, which is much quicker than that observed in other two-dimensional materials. KPFM characterizations indicate that air molecules’ adsorption alters the surface potentials of SiO₂, SnS, metal electrodes, and contacts with minimal impact on the electrode contact surface potential. Upon the adsorption of NH₃ molecules or air molecules, the hole concentration within the device decreases. These findings elucidate the adsorption mechanism of NH₃ molecules on SnS, potentially fostering the advancement of rapid gas sensing applications utilizing two-dimensional ferroelectrics.

Broad-bandgap semiconductor-based solar-blind ultraviolet (SBUV) photodetectors have attracted considerable research interest because of their broad applications in missile plume tracking, flame detectors, environmental monitoring, and optical communications due to their solar-blind nature and high sensitivity with low background radiation. Owing to its high light absorption coefficient, abundance, and wide tunable bandgap of 2-2.6 eV, tin disulfide (SnS₂) has emerged as one of the most promising compounds for application in UV-visible optoelectronic devices. However, SnS₂ UV detectors have some undesirable properties such as slow response speed, high current noise level, and low specific detectivity. This study reports a metal mirror-enhanced Ta_0.01W_0.99Se₂/SnS₂ (TWS) van der Waals heterodiode-based SBUV photodetector with an ultrahigh photoresponsivity (R) of ∼1.85 × 10⁴ AW^-1 and a fast speed with rising time (τ_r) of 3.3 μs and decay time (τ_d) of 3.4 μs. Notably, the TWS heterodiode device exhibits a significantly low noise equivalent power of ∼1.02 × 10^-18 W Hz^-1/2 and a high specific detectivity of ∼3.65 × 10¹⁴ cm Hz^1/2 W^-1. This study provides an alternative method for designing fast-speed SBUV photodetectors with enormous potential in applications.

Driven by the unique linear dichroism feature of anisotropic two‐dimensional (2D) materials, much attempt has been made to introduce artificial anisotropy into isotropic 2D materials to deliver polarization‐sensitive performance. However, those methods have not been widely promoted because of technical limitations. This paper reports on the successful modulation to the structural symmetry of WSe₂ through van der Waals (vdW) interlayer coupling. Correspondingly, both the polarized Raman and photoluminescence (PL) spectra of WSe₂ in heterostructure exhibit periodic variation tendency. Similarly, direction‐sensitive electronic transport has also been observed in WSe₂/CrOCl heterostructure, and the conductance along armchair direction is ≈1.5 times of that along zigzag direction. As a functional illustration to the interlayer coupling induced linear dichroism, angle‐dependent photodetection is conducted to WSe₂/CrOCl device. With light irradiation at 532 nm, the device photocurrent along armchair direction is 1.27 times higher than that along zigzag direction. The abnormal linear dichroism of WSe₂ in the study clearly proves that few‐layer WSe₂ on CrOCl flake has been entitled with artificial anisotropy. The interlayer coupling method is feasible and practical in 2D‐material range, offering the possibility to develop polarization‐dependent electronic, pyroelectric, and photoelectric devices from isotropic 2D materials.