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With distinctive phase-change and switching properties, chalcogenide materials have emerged as critical components in various cutting-edge technologies. This review attempts to provide an overview of chalcogenide materials, from their fundamental properties to their diverse applications with focus on memory and sensing technologies, which are indispensable components in human-like electronic artificial sensory systems. After reviewing the synthesis and application of chalcogenide materials with respect to dimensionality, we focus on the key advances in (1) memory devices, including phase-change memory (PCM), ovonic threshold switching (OTS) selectors, and selector-only memory (SOM), and (2) sensing devices, including optical sensors, gas sensors, and neuromorphic sensors. Emphasis will be given on how chalcogenide materials can be integrated into next-generation systems, such as wearable platforms, artificial intelligence, and neuromorphic/quantum computing systems, to meet the growing demands for high-performance memory and multi-functional sensing. We also provide an overview of emerging research trends as well as a comprehensive perspective on the current status of research on chalcogenides. Finally, we attempt to provide insights into how chalcogenides can continue to drive technological breakthroughs in both memory and sensing applications while shaping the future landscape of intelligent systems, smart sensing platforms, and sustainable technology development.

The results of study of charge transfer processes in thin amorphous and crystalline Sb2Te3 films in a wide range of frequencies and temperatures are presented. The frequency spectra of conductivity were obtained by the dielectric spectroscopy method. The authors analyzed the frequency dependences of the conductivity in the electric field and the temperature dependences of the exponent s. A transition from the classical correlated barrier hopping (CBH) to quantum mechanical tunneling (QMT) was observed at a certain temperature Tt. The CBH model allowed the authors to calculate the conductivity parameters of two phases. Two areas with different types of conductivity were revealed on the conduction spectra, and the activation energies of charge transfer processes for amorphous and crystalline films were determined. The following features were discovered: the difference in the temperatures of the change of the charge transfer mechanism and the transition from the semiconductor region to the metal region on the temperature dependence of conductivity. They can help to identify the amorphous phase in the quasi-binary chalcogenide Sb2Te3-GeTe system.

The long-wavelength moiré superlattices in twisted 2D structures have emerged as a highly tunable platform for strongly correlated electron physics. We study the moiré bands in twisted transition metal dichalcogenide homobilayers, focusing on WSe 2 , at small twist angles using a combination of first principles density functional theory, continuum modeling, and Hartree-Fock approximation. We reveal the rich physics at small twist angles θ  < 4 ∘ , and identify a particular magic angle at which the top valence moiré band achieves almost perfect flatness. In the vicinity of this magic angle, we predict the realization of a generalized Kane-Mele model with a topological flat band, interaction-driven Haldane insulator, and Mott insulators at the filling of one hole per moiré unit cell. The combination of flat dispersion and uniformity of Berry curvature near the magic angle holds promise for realizing fractional quantum anomalous Hall effect at fractional filling. We also identify twist angles favorable for quantum spin Hall insulators and interaction-induced quantum anomalous Hall insulators at other integer fillings. The e moiré superlattice in twisted 2D structures becomes a highly tunable platform of strongly correlated electron systems. Here, the authors predict rich physics at small twist angles in twisted transition metal dichalcogenide bilayers, including a magic angle for flat band, interaction-driven Haldane insulator, fractional quantum anomalous Hall effect and quantum spin Hall insulators.

The family of transition metal chalcogenides, particularly barium titanium trisulphide (BaTiS3 $\\text{BaTi}\\mathrm{S}_{3}$ ), is one of the classes of materials that have garnered a lot of interest recently, owing to their unique combination of structural versatility, environmental stability, and tunable electronic properties. However, controlled doping of these materials, as is necessary for customizing their electrical and electronic properties, is one of the several challenges still being faced by researchers. Studies on dopant incorporation processes on these materials are yet to be comprehensively determined. In this research paper, two new materials (BaTi0.5Mn0.5S3 $\\mathrm{BaTi}_{0.5}\\mathrm{Mn}_{0.5}\\mathrm{S}_{3}$and BaTi0.5Mn0.5Se3 $\\mathrm{BaTi}_{0.5}\\mathrm{Mn}_{0.5}\\mathrm{Se}_{3}$ ) were modelled from the BaTiS3 $\\text{BaTi}\\mathrm{S}_{3}$and their electronic and transport properties investigated using density functional theory calculations as implemented in the Quantum Espresso package. The Perdew–Burke–Ernzerhof exchange‐correlation functional was utilized. It was found out that the substitution resulted in lowering the electrical conductivities, carrier mobilities, and formation energies compared to the original sample, while their densities increased. The results also pointed to the adjustment of the materials’ band gaps from 0.71 eV for the original sample to as low as 0.312 eV in the BaTi0.5Mn0.5Se3 $\\mathrm{BaTi}_{0.5}\\mathrm{Mn}_{0.5}\\mathrm{Se}_{3}$sample. Regardless of the changes, the Hall coefficients of the samples turned out to be p‐type, whose values increased with the substitutions. The above findings underline the significance of compositional adjustment in maximizing the performance of BaTiS3 $\\text{BaTi}\\mathrm{S}_{3}$and its derivatives in photovoltaic, thermoelectric, and sensor applications. We investigated the effect of manganese and selenium substitution on BaTiS3 using density functional theory calculations performed with Quantum Espresso. Elemental tuning narrows the band gap from 0.71 to 0.312 eV, slightly modifies stability and conductivity, and preserves p‐type behavior, highlighting the potential of controlled doping for energy‐related applications.

The crystal structure of a material creates a periodic potential that electrons move through giving rise to its electronic band structure. When two-dimensional materials are stacked, the resulting moiré pattern introduces an additional periodicity so that the twist angle between the layers becomes an extra degree of freedom for the resulting heterostructure. As this angle changes, the electronic band structure is modified leading to the possibility of flat bands with localized states and enhanced electronic correlations 1 – 6 . In transition metal dichalcogenides, flat bands have been theoretically predicted to occur for long moiré wavelengths over a range of twist angles around 0° and 60° (ref. 4 ) giving much wider versatility than magic-angle twisted bilayer graphene. Here, we show the existence of a flat band in the electronic structure of 3° and 57.5° twisted bilayer WSe 2 samples using scanning tunnelling spectroscopy. Our direct spatial mapping of wavefunctions at the flat-band energy show that the localization of the flat bands is different for 3° and 57.5°, in agreement with first-principles density functional theory calculations 4 . Using scanning tunnelling spectroscopy, the flat bands in twisted bilayer WSe 2 are shown near both 0° and 60° twist angles.

The intrinsic light–matter characteristics of transition-metal dichalcogenides have not only been of great scientific interest but have also provided novel opportunities for the development of advanced optoelectronic devices. Among the family of transition-metal dichalcogenide structures, the one-dimensional nanotube is particularly attractive because it produces a spontaneous photocurrent that is prohibited in its higher-dimensional counterparts. Here, we show that WS 2 nanotubes exhibit a giant shift current near the infrared region, amounting to four times the previously reported values in the higher frequency range. The wall-to-wall charge shift constitutes a key advantage of the one-dimensional nanotube geometry, and we consider a Janus-type heteroatomic configuration that can maximize this interwall effect. To assess the nonlinear effect of a strong field and the nonadiabatic effect of atomic motion, we carried out direct real-time integration of the photoinduced current using time-dependent density functional theory. Our findings provide a solid basis for a complete quantum mechanical understanding of the unique light–matter interaction hidden in the geometric characteristics of the reduced dimension. We demonstrate that double-wall or multi-wall WS 2 nanotubes can exhibit unexpectedly efficient bulk photovoltaic effect owing to its unique inter-wall charge-shifting excitations.

HighlightsUnique “Janus” interfacial assemble strategy of 2D MXene nanosheets was proposed firstly.Ternary heterostructure consisting of high capacity transitional metal chalcogenide, high conductive 2D MXene and N rich fungal carbonaceous matrix was achieved for larger radius Na/K ions storages.The highly accessible surfaces and interfaces of the strongly coupled 2D based ternary heterostructures provide superb surficial pseudocapacitive storages for both Na and K ions with low energy barriers was verified.Combining with the advantages of two-dimensional (2D) nanomaterials, MXenes have shown great potential in next generation rechargeable batteries. Similar with other 2D materials, MXenes generally suffer severe self-agglomeration, low capacity, and unsatisfied durability, particularly for larger sodium/potassium ions, compromising their practical values. In this work, a novel ternary heterostructure self-assembled from transition metal selenides (MSe, M = Cu, Ni, and Co), MXene nanosheets and N-rich carbonaceous nanoribbons (CNRibs) with ultrafast ion transport properties is designed for sluggish sodium-ion (SIB) and potassium-ion (PIB) batteries. Benefiting from the diverse chemical characteristics, the positively charged MSe anchored onto the electronegative hydroxy (–OH) functionalized MXene surfaces through electrostatic adsorption, while the fungal-derived CNRibs bonded with the other side of MXene through amino bridging and hydrogen bonds. This unique MXene-based heterostructure prevents the restacking of 2D materials, increases the intrinsic conductivity, and most importantly, provides ultrafast interfacial ion transport pathways and extra surficial and interfacial storage sites, and thus, boosts the high-rate storage performances in SIB and PIB applications. Both the quantitatively kinetic analysis and the density functional theory (DFT) calculations revealed that the interfacial ion transport is several orders higher than that of the pristine MXenes, which delivered much enhanced Na+ (536.3 mAh g−1@ 0.1 A g−1) and K+ (305.6 mAh g−1@ 1.0 A g−1 ) storage capabilities and excellent long-term cycling stability. Therefore, this work provides new insights into 2D materials engineering and low-cost, but kinetically sluggish post-Li batteries.

Monoclinic transition metal dichalcogenides offer the possibility of topological quantum devices, but they are difficult to realize. One route may be through switching from the common hexagonal phase, for which a method is now shown. Layered transition metal dichalcogenides (TMDs) have attracted renewed interest owing to their potential use as two-dimensional components in next-generation devices 1 , 2 . Although group 6 TMDs, such as MX 2 with M = (Mo, W) and X = (S, Se, Te), can exist in several polymorphs 3 , most studies have been conducted with the semiconducting hexagonal (2H) phase as other polymorphs often exhibit inhomogeneous formation 1 , 4 , 5 , 6 . Here, we report a reversible structural phase transition between the hexagonal and stable monoclinic (distorted octahedral or 1T′) phases in bulk single-crystalline MoTe 2 . Furthermore, an electronic phase transition from semimetallic to semiconducting is shown as 1T′-MoTe 2 crystals go from bulk to few-layered. Bulk 1T′-MoTe 2 crystals exhibit a maximum carrier mobility of 4,000 cm 2 V −1 s −1 and a giant magnetoresistance of 16,000% in a magnetic field of 14 T at 1.8 K. In the few-layered form, 1T′-MoTe 2 exhibits a bandgap opening of up to 60 meV, which our density functional theory calculations identify as arising from strong interband spin–orbit coupling. We further clarify that the Peierls distortion is a key mechanism to stabilize the monoclinic structure. This class of semiconducting MoTe 2 unlocks the possibility of topological quantum devices based on non-trivial Z 2 -band-topology quantum spin Hall insulators in monoclinic TMDs (ref.  7 ).

Two-dimensional (2D) semiconductors, especially transition metal dichalcogenides (TMDs), have been envisioned as promising candidates in extending Moore’s law. To achieve this, the controllable growth of wafer-scale TMDs single crystals or periodic single-crystal patterns are fundamental issues. Herein, we present a universal route for synthesizing arrays of unidirectionally orientated monolayer TMDs ribbons (e.g., MoS 2 , WS 2 , MoSe 2 , WSe 2 , MoS x Se 2-x ), by using the step edges of high-miller-index Au facets as templates. Density functional theory calculations regarding the growth kinetics of specific edges have been performed to reveal the morphological transition from triangular domains to patterned ribbons. More intriguingly, we find that, the uniformly aligned TMDs ribbons can merge into single-crystal films through a one-dimensional edge epitaxial growth mode. This work hereby puts forward an alternative pathway for the direct synthesis of inch-scale uniform monolayer TMDs single-crystals or patterned ribbons, which should promote their applications as channel materials in high-performance electronics or other fields. Here, the authors report the direct growth of periodic arrays of 2D semiconductor ribbons by exploiting the step edges of high-miller-index Au facets, showing potential for 2D electronic devices. The synthesized ribbons could also be merged to obtain wafer-scale single-crystal monolayers.

Chalcogen vacancies are generally considered to be the most common point defects in transition metal dichalcogenide (TMD) semiconductors because of their low formation energy in vacuum and their frequent observation in transmission electron microscopy studies. Consequently, unexpected optical, transport, and catalytic properties in 2D-TMDs have been attributed to in-gap states associated with chalcogen vacancies, even in the absence of direct experimental evidence. Here, we combine low-temperature non-contact atomic force microscopy, scanning tunneling microscopy and spectroscopy, and state-of-the-art ab initio density functional theory and GW calculations to determine both the atomic structure and electronic properties of an abundant chalcogen-site point defect common to MoSe 2 and WS 2 monolayers grown by molecular beam epitaxy and chemical vapor deposition, respectively. Surprisingly, we observe no in-gap states. Our results strongly suggest that the common chalcogen defects in the described 2D-TMD semiconductors, measured in vacuum environment after gentle annealing, are oxygen substitutional defects, rather than vacancies. The nature of defects in transition metal dichalcogenide semiconductors is still under debate. Here, the authors determine the atomic structure and electronic properties of chalcogen-site point defects common to monolayer MoSe 2 and WS 2 , and find that these are substitutional defects, where a chalcogen atom is substituted by an oxygen atom, rather than vacancies.