Xiangchao Ma

拓扑节线半金属ZrSiS因其独特的电子结构而在体相材料中展现出丰富的物理现象。然而，对其低维形式（如单层和双层）的光学与表面等离激元性质的研究尚不充分。基于第一性原理计算，本工作系统地研究了单层和双层 ZrSiS 的电子能带结构、光电导率、光学性质和表面等离子体激元极化激元（SPP）特性。计算结果表明，层状 ZrSiS 由于其拓扑节线能带而表现出独特的光电导特性，在红外区域显示出显著的带内响应，同时在可见光范围内显示出明显的带间响应。此外其光学性质表明，单层和双层结构都具有很高的光吸收率（显著超过石墨烯）以及从红外到可见光谱的可调反射/透射窗口。此外，我们发现单层和双层ZrSiS在表面等离激元特性上支持从红外到可见光范围的表面等离激元（单层:0.5 - 4 eV；双层：0.4 - 2.5 eV）。这些表面等离激元相较于体材料表现出更为出色的局域化特性。综上所述，层状 ZrSiS 在纳米光子学、高性能红外光电探测器以及可调谐等离子体器件的应用方面具有巨大潜力。

This study combines density functional theory (DFT) calculations with systematic analysis to reveal the unique properties of a novel 2D Janus MoSTe/MoTe₂ heterostructure. The most stable configuration is identified as an AD-stacked heterojunction with an interlayer spacing of 6.73 Å, supported by minimal binding energy (−2.24 meV Å⁻¹) and validated through phonon dispersion spectra and molecular dynamics simulations. The heterojunction exhibits a type-II band alignment with a 0.39 eV direct bandgap, where electrons are transferred from the MoSTe side to the MoTe₂ side at the interlayer position, creating a built-in electric field. That enhances electron–hole separation efficiency—a critical feature for optoelectronic applications. Optical calculations demonstrate strong ultraviolet absorption with a peak coefficient of 12.8 μm⁻¹ at 5.4 eV, it has excellent performance and is expected to become a promising candidate for ultraviolet photodetectors. Notably, the system displays exceptional strain sensitivity: compressive strain (−2%) induces a reversible type-II to type-I transition, while 2% tensile strain triggers a semiconductor-to-metal transition, evolving into a Dirac-cone-like band structure at 4% tensile strain. Mechanically, the heterojunction shows anisotropic flexibility, coupled with a Poisson’s ratio of 0.36 that decreases sharply under strain, indicating tunable mechanical response. Combined with its robust UV absorption (12.8 μm⁻¹ at 5.4 eV), moderate visible-light transmittance, and strain-mediated electronic transitions, these properties establish the Janus MoSTe/MoTe₂ heterostructure as a highly adaptable material for next-generation flexible optoelectronics.

Non-radiative decay of surface plasmon (SP) offers a novel paradigm for efficient conversion of photons into carriers. However, the narrow bandwidth of SP has been a significant obstacle to the widespread applications. Previously, research and applications mainly focused on noble metals such as Au, Ag, and Cu. In this article, we report an Ag-Al alloy material, μ-Ag₃Al, in which the surface plasmon operating bandwidth is 1.7 times that of Ag and hot carrier transport properties are comparable with those of AuAl. The results show that μ-Ag₃Al allows efficient direct interband electronic transitions from ultraviolet (UV) to near infrared range. Spherical nanoparticles of μ-Ag₃Al exhibit the localized surface plasmon resonance (LSPR) effect in the ultraviolet region. Its surface plasmon polariton (SPP) shows strong non-radiative decay at 3.36 eV, which is favorable for the generation of high-energy hot carriers. In addition, the penetration depth of SPP in μ-Ag₃Al remains high across the UV to the near-infrared range. Moreover, the transport properties of hot carriers in μ-Ag₃Al are comparable with those in Al, borophene and Au-Al intermetallic compounds. These properties can provide guidance for the design of plasmon-based photodetectors, solar cells, and photocatalytic reactors.

Transition metal dichalcogenides (TMDs) have excellent optical and mechanical properties and have potential application value in wearable optoelectronic response devices. MoTe₂, a representative material of TMDs, is studied by first-principles calculation in this paper. The results show that the MoTe₂ monolayer has a direct band gap of 1.110eV, which has a strong light absorption capacity and can produce a high concentration of photogenerated charge carriers after light absorption. The material is soft and exhibits the unique mechanical properties of layered materials. The effects of biaxial strain and defects on the properties of the materials were analyzed. The results show that the biaxial compression strain can enhance the light absorption curve of the material, enhance the light absorption of the photogenerated carrier, and expand the range of its energy distribution. The tensile strain decreases the value of the photon absorption curve and decreases the range of energy distribution of photogenerated carriers. The Mo vacancy defect increases the absorption curve value in the low energy region and broadens the optical response range of the material. The two types of vacancy defects both induce a ‘discrete’ distribution of photogenerated carriers. The Mo vacancy significantly affects the elastic modulus and anisotropy properties of the material, resulting in the material changing from ductile to brittle. When Mo vacancy is added, the spatial distribution of the elastic modulus of the material also changes greatly. Therefore, MoTe₂ has potential application in flexible optoelectronic devices, and its performance can be controlled by strains and defects.

Unlike conventional optoelectronic devices, plasmon-driven optoelectronic devices can efficiently realize energy conversion and regulate the energy distribution of hot carriers through high-energy, non-equilibrium “hot” electron-hole pairs (hot carriers) generated by surface plasmon non-radiative decay, thereby presenting new opportunities for realizing hot carrier optoelectronic devices. As the basis for the practical application of plasmon optoelectronic devices, searching for plasmon metal materials with exceptional performance has always been an important topic in the field of hot carrier optoelectronic devices. Currently, MXenes can be synthesized on a large scale and has excellent photoelectric properties, so it can be used to build a variety of hot carrier photodetectors with unique structures and functions. Unlike the fixed surface ends of two-dimensional materials such as graphene, MoS2 and borophene, MXenes has an abundance of surface functional groups. However, the increase of ambient temperature will accelerate the oxidation modification of surface functional groups, thus affecting the life and performance stability of optoelectronic devices. In view of the inherent limitations of experimental research on dynamic characteristics of hot carriers at continuous temperatures, we study the temperature effects on the electronic state distributions and scattering effects by using the theory of multi-body perturbation and quantum mechanics. Particularly, we introduce temperature effect into interband electron transition and phonon-assisted electron transition process to obtain temperature dependent dielectric function. From the perspective of non-radiative decay of surface plasmon, we quantify the hot carrier generation efficiency, energy distribution and transport characteristics by first principles calculations, in order to systematically study the ambient temperature dependence of plasmon-induced hot carriers in MXenes. The results show that the interband transition and the phonon-assisted electron transition in MXenes together efficiently produce high-energy hot hole-dominated carriers with a long lifetime and transport distance, which is comparable to borophene. The increase of ambient temperature significantly improves the hot carrier generation efficiency in the infrared range. Meanwhile, the physical mechanism of hot carrier generation in visible light is almost unaffected by the increase of ambient temperature, and the generated hot holes show excellent ambient temperature stability. In addition, the lifetime and transport distance of hot carriers decrease with ambient temperature increasing, which is mainly due to the enhanced scattering of electrons and optical phonons. The research results will provide theoretical and data support for quantitatively evaluating the ambient temperature stability of MXenes plasmon optoelectronic devices in practical environment.

MoSSe材料是非常有前途的光电材料，它的应用环境会接触到水溶液，但是目前尚未有关于MoSSe材料在水溶液中电化学稳定性的研究。本文基于密度泛函理论构建不同钼、硫和硒元素原子比例的单层MoSSe的Pourbaix图，研究在不同pH和电极电位条件下的热力学稳定性和电化学腐蚀行为。对MoSSe的Pourbaix图研究表明，一部分MoSSe的免蚀区域存在于Pourbaix图中水的稳定区域内，说明MoSSe在水环境中可以稳定存在；相比较碱性溶液来说，MoSSe在酸性和中性溶液中的耐腐蚀性更好。对Mo₄S₂Se₆、Mo₄S₆Se₂、Mo₄S₇Se和Mo₄SSe₇的Pourbaix图研究表明，在不同钼、硫和硒元素原子比例的单层MoSSe中硫的摩尔分数高的情况下，材料在水溶液中可以稳定存在的条件范围变大，耐腐蚀性变好；在不同钼、硫和硒元素原子比例的单层MoSSe中硒的摩尔分数高的情况下，材料在水溶液中可以稳定存在的条件范围变小，耐腐蚀性变差。本文对不同钼、硫和硒元素原子比例的单层MoSSe在水溶液中的稳定性和腐蚀行为进行预测，更加深入地探究了MoSSe材料在水溶液中的降解行为，可以对钼硫硒材料在光电领域的应用提供理论指导。

Plasmonic materials that exhibit excellent plasmonic behavior at high temperatures would greatly expand existing applications, but the search for such materials is ongoing. Transition metal nitrides with good conductivity and high-temperature stability are promising candidates for temperature-dependent plasmonic applications. Here, we systematically investigate the temperature-dependent surface plasmon and hot carrier properties of TiN and VN. Significantly, high temperatures significantly affect the phonon-assisted intraband transition processes. Meanwhile, TiN and VN exhibit efficient optical absorption and low surface plasmon loss at different temperatures, which are comparable to or even higher than Ag. In particular, the surface plasmon response of TiN extends to visible light, making it an excellent candidate for low-loss and broadband plasmonic applications at high temperatures. In contrast, VN exhibits a much narrower plasmonic window, which is mainly suitable for infrared low-loss plasmonic devices. For hot carriers, the energy and probability distributions of hot holes in TiN and hot electrons in VN exhibit robustness to temperature. Meanwhile, transport properties indicate that the temperature effect on hot holes is significantly higher than that on hot electrons in TiN and VN. Therefore, we expect that the reported results will provide theoretical guidance for the design of next-generation high-temperature plasmonic devices.

We have systematically studied the electronic structures, dielectric function, SP, hot carrier generation and transport properties of KV₃Sb₅. The results indicate the potential of KV₃Sb₅ for plasmon-mediated hot carrier applications.