Wafer-Scale Atomic Layer-Deposited TeOx/Te Heterostructure P-Type Thin-Film Transistors.

There is an increasing demand for p-type semiconductors with scalable growth, excellent device performance, and back-end-of-line (BEOL) compatibility. Recently, tellurium (Te) has emerged as a promising candidate due to its appealing electrical properties and potential low-temperature production. So far, nearly all of the scalable production and integration of Te with complementary metal oxide semiconductor (CMOS) technology have been based on physical vapor deposition. Here we demonstrate wafer-scale atomic layer-deposited (ALD) TeOx/Te heterostructure thin-film transistors with high uniformity and integration compatibility. The wafer-scale uniformity of the film is evidenced by spatial Raman mappings and statistical electrical analysis. Furthermore, surface accumulation-induced good ohmic contact has been observed and explained by the unique band alignment of the charge neutrality level inside the Te valence band. These results demonstrate ALD TeOx/Te as a promising p-type semiconductor for monolithic three-dimensional integration in BEOL CMOS applications incorporated with well-established n-type ALD oxide semiconductors.

Gate Modulation of Dissipationless Nonlinear Quantum Geometric Current in 2D Te.

Two-dimensional trigonal tellurium (2D Te), a narrow-bandgap semiconductor with a bandgap of approximately 0.3 eV, hosts Weyl points near the band edge and exhibits a narrow, strong Berry curvature dipole (BCD). By applying a back-gate bias to align the Fermi level with the BCD, a sharp increase in the dissipationless transverse nonlinear Hall response is observed in 2D Te. Gate modulation of the BCD demonstrates an on/off ratio of 104 and a responsivity of nearly 106 V/W, while the longitudinal current induced by band modulation reaches an on/off ratio of about 10. This current is sustained up to 200 K, exhibiting a change of 3 orders of magnitude. The inclusion of both transistor action and rectification enhances the temperature sensitivity of the dissipationless Hall current, offering potential applications in electrothermal detectors and sensors and highlighting the significance of topological properties in advancing electronic applications.

Lead-Free Perovskite With Efficient Tellurium Ion Activation for Multifunctional Applications.

Lead-free perovskite materials have received extensive attention due to their non-toxicity, super environmental stability and adjustable photoelectric properties. However, the inherent problems of low luminous efficiency and low photoluminescence quantum yields (PLQYs) limit its development in multifunctional applications. Here, Te4+ doped Cs2ZrCl6 with high luminous efficiency and stability for multifunctional applications are developed. Te4+ ions are used as emission centers to improve the optical properties of Cs2ZrCl6 to make efficient and stable single-component white light-emitting diodes (WLEDs), and can be used as scintillator materials to improve scintillation performance to achieve high-resolution and low-dose X-ray imaging detection. In addition, it is found for the first time that Te4+ ions can be introduced into the trap center, so that the Cs2ZrCl6:Te4+ perovskite material exhibits excellent persistent luminescence (PersL) and mechanoluminescence (ML) after X-ray radiation, which has potential applications in the fields of delayed imaging and stress sensing. This work provides a method for designing lead-free perovskites with high optical performance and scintillating properties, as well as developing multifunctional applications.

Beyond Conventional Catalysts: Monoelemental Tellurium as a Game Changer for Piezo-Driven Hydrogen Evolution.

The increasing demand for clean hydrogen production over fossil fuels necessitates the development of sustainable piezoelectrochemical methods that can overcome the limitations of conventional electrocatalytic and photocatalytic approaches. In this regard, existing piezocatalysts face challenges related to their low piezoelectricity or active site coverage for hydrogen evolution reaction (HER). Driven by global environmental concerns, there is a compelling push to engineer practical materials for highly efficient HER. Herein, monoelemental 2D tellurium (Te) is presented as a class of layered chalcogenide with a non-centrosymmetric crystal structure (P3121 space group). The refined Te nanosheets demonstrate an unprecedented highly efficient H2 production rate ≈9000 µmol g-1 h-1 under ultrasonic mechanical vibration due to built-in piezo-potential in the system. The remarkable piezocatalytic performance of Te nanosheets arises from a synergistic interplay between their semi-metallic nature, favorable free energy landscape, enhanced electrical conductivity and outstanding piezoelectricity. As a proof of concept, the theoretical approach based on Density Functional Theory (DFT) validates the findings due to the gradual exposure of active sites on the Te nanosheets leading to a self-optimized catalytic performance for hydrogen generation. Therefore, mechanically driven Te emerges as a promising piezocatalyst with the potential to revolutionize highly efficient and sustainable technology for futuristic applications.

Synthesis, Properties, and Application of Ultrathin and Flexible Tellurium Nanorope Films: Beyond Conventional 2D Materials.

Nanomaterials that can be easily processed into thin films are highly desirable for their wide range of applicability in electrical and optical devices. Currently, Te-based 2D materials are of interest because of their superior electrical properties compared to transition metal dichalcogenide materials. However, the large-scale manufacturing of these materials is challenging, impeding their commercialization. This paper reports on ultrathin, large-scale, and highly flexible Te and Te-metal nanorope films grown via low-power radiofrequency sputtering for a short period at 25 °C. Additionally, the feasibility of such films as transistor channels and flexible transparent conductive electrodes is discussed. A 20 nm thick Te-Ni-nanorope-channel-based transistor exhibits a high mobility (≈450 cm2 V-1 s-1 ) and on/off ratio (105 ), while 7 nm thick Te-W nanorope electrodes exhibit an extremely low haze (1.7%) and sheet resistance (30 Ω sq-1 ), and high transmittance (86.4%), work function (≈4.9 eV), and flexibility. Blue organic light-emitting diodes with 7 nm Te-W anodes exhibit significantly higher external quantum efficiencies (15.7%), lower turn-on voltages (3.2 V), and higher and more uniform viewing angles than indium-tin-oxide-based devices. The excellent mechanical flexibility and easy coating capability offered by Te nanoropes demonstrate their superiority over conventional nanomaterials and provide an effective outlet for multifunctional devices.

Enhanced Sensitivity in Photovoltaic 2D MoS2/Te Heterojunction VOC Sensors.

Volatile organic compound (VOC) sensors have a broad range of applications including healthcare monitoring, product quality control, and air quality management. However, many such applications are demanding, requiring sensors with high sensitivity and selectivity. 2D materials are extensively used in many VOC sensing devices due to their large surface-to-volume ratio and fascinating electronic properties. These properties, along with their exceptional flexibility, low power consumption, room-temperature operation, chemical functionalization potential, and defect engineering capabilities, make 2D materials ideal for high-performance VOC sensing. Here, a 2D MoS2/Te heterojunction is reported that significantly improves the VOC detection compared to MoS2 and Te sensors on their own. Density functional theory (DFT) analysis shows that the MoS2/Te heterojunction significantly enhances the adsorption energy and therefore sensing sensitivity of the sensor. The sensor response, which denotes the percentage change in the sensor's conductance upon VOC exposure, is further enhanced under photo-illumination and zero-bias conditions to values up to ≈7000% when exposed to butanone. The MoS2/Te heterojunction is therefore a promising device architecture for portable and wearable sensing applications.

Affinity of Telluronium Chalcogen Bond Donors for Lewis Bases in Solution: A Critical Experimental-Theoretical Joint Study.

Telluronium salts [Ar2 MeTe]X were synthesized, and their Lewis acidic properties towards a number of Lewis bases were addressed in solution by physical and theoretical means. Structural X-ray diffraction analysis of 21 different salts revealed the electrophilicity of the Te centers in their interactions with anions. Telluroniums' propensity to form Lewis pairs was investigated with OPPh3 . Diffusion-ordered NMR spectroscopy suggested that telluroniums can bind up to three OPPh3 molecules. Isotherm titration calorimetry showed that the related heats of association in 1,2-dichloroethane depend on the electronic properties of the substituents of the aryl moiety and on the nature of the counterion. The enthalpies of first association of OPPh3 span -0.5 to -5 kcal mol-1 . Study of the affinity of telluroniums for OPPh3 by state-of-the-art DFT and ab-initio methods revealed the dominant Coulombic and dispersion interactions as well as an entropic effect favoring association in solution. Intermolecular orbital interactions between [Ar2 MeTe]+ cations and OPPh3 are deemed insufficient on their own to ensure the cohesion of [Ar2 MeTe ⋅ Bn ]+ complexes in solution (B=Lewis base). Comparison of Grimme's and Tkatchenko's DFT-D4/MBD-vdW thermodynamics of formation of higher [Ar2 MeTe ⋅ Bn ]+ complexes revealed significant molecular size-dependent divergence of the two methodologies, with MBD yielding better agreement with experiment.

An Unusual Macrocyclic Hexamer of an Iso-Tellurazole N-Oxide Featuring CTe O Chalcogen Bonds is Formed by κ6 -O Complexation to Fe(II) and Ni(II).

Studies of the supramolecular chemistry of iso-tellurazole N-oxides have been confined to non-polar media until now. To overcome that limitation, an iso-tellurazole N-oxide was derivatized with a primary alcohol group; the compound is soluble in polar solvents and stable in acidic to neutral aqueous media. Nickel (II) and iron (II) form macrocyclic complexes with six molecules of that iso-tellurazole N-oxide in a hitherto not-observed macrocyclic arrangement defined by CTe⋅⋅⋅O chalcogen bonds and κ6 -O bound to the metal ion. This behaviour is in sharp contrast with the κn -Te (n=1,2,4) complexes formed by soft metal ions.

Telluronium-Catalyzed Halogenation Reactions: Chalcogen-Bond Activation of N-Halosuccinimides and Catalysis.

The ability of triaryltelluronium salts to interact with N-halosuccinimides (NXS) through chalcogen bonding (ChB) in the solid state and in solution is demonstrated herein. Cocrystals of the triaryltelluronium bearing two CF3 electron-withdrawing groups per aryl ring with N-chloro-, N-bromo- and N-iodosuccinimide (respectively NCS, NBS and NIS) were analyzed by X-ray diffraction, evidencing a ChB between tellurium and the carbonyl group of NXS. This ChB was confirmed in solution by NMR spectroscopy, especially by 125Te NMR titration experiment, which allowed the determination of the association constant (Ka) between the telluronium and NBS. The so-obtained Ka value of 17.3±0.6 M-1 indicated a moderate interaction in solution because of the competitive role of the solvent. The strength of the Te⋅⋅⋅O ChB was however sufficient enough to promote the catalytic halofunctionalization of aromatics and of alkenes such as the intra- and intermolecular haloalkoxylation and haloesterification of alkenes.

Bidentate Ligand Driven Intramolecularly Te O Bonded Organotellurium Cations from Synthesis, Stability to Catalysis.

A new series of unsymmetrical phenyl tellurides derived from 2-N-(quinolin-8-yl) benzamide ligand has been synthesized in a practical manner by the copper-catalyzed method by using diaryl ditelluride and Mg as a reductant at room temperature. In order to augment the Lewis acidity of these newly formed unsymmetrical monotellurides, these have been transformed into corresponding unsymmetrical 2-N-(quinolin-8-yl)benzamide tellurium cations. Subsequently, these Lewis acidic tellurium cations were used as chalcogen bonding catalysts, enabling the synthesis of various substituted 1,2-dihydroquinolines by activating ketones with anilines under mild conditions. Moreover, the synthesized 2-N-(quinolin-8-yl)benzamide phenyl tellurium cation has also catalyzed the formation of ß-amino alcohols in high regioselectivity by effectively activating epoxides at room temperature. Mechanistic insight by 1 H and 19 F NMR study, electrostatic surface potential (ESP map), control reaction in which tellurium cation reacted explosively with epoxide, suggested that the enhanced Lewis acidity of tellurium center seems responsible for efficient catalytic activities under mild conditions enabling ß-amino alcohols with excellent regioselectivity and 1,2-dihydroquinolines with trifluoromethyl, nitro, and pyridylsubstitution, which were difficult to access.

Cationic Hypervalent Chalcogen Bond Catalysis on the Povarov Reaction: Reactivity and Stereoselectivity.

Chalcogen bond catalysis, particularly cationic hypervalent chalcogen bond catalysis, is considered to be an effective strategy for organocatalysis. In this work, the cationic hypervalent chalcogen bond catalysis for the Povarov reaction between N-benzylideneaniline and ethyl vinyl ether was investigated by density functional theory (DFT). The catalytic reaction involves the cycloaddition process and the proton transfer process, and the rate-determining step is the cycloaddition process. Cationic hypervalent tellurium derivatives bearing CF3 and F groups exhibit superior catalytic activity. For the rate-determining step, the Gibbs free energy barrier decreases as the positive electrostatic potential of the chalcogen bond catalysts increases. More importantly, the Gibbs free energy barrier has a strong linear correlation with the electrostatic energy of the chalcogen bond in the catalyst-substrate complex. Furthermore, the catalytic reactions include the endo pathway and exo pathway. The C-H⋅⋅⋅π interaction between the substituent of the ethyl vinyl ether and the aryl ring of the N-benzylideneaniline contributes to the endo-selectivity of the reaction. This research contributes to a deeper understanding of chalcogen bond catalysis, providing insights for designing chalcogen bond catalysts with high performance.

Telluride-Based Materials: A Promising Route for High Performance Supercapacitors.

As supercapacitor (SC) technology continues to evolve, there is a growing need for electrode materials with high energy/power densities and cycling stability. However, research and development of electrode materials with such characteristics is essential for commercialization the SC. To meet this demand, the development of superior electrode materials has become an increasingly critical step. The electrochemical performance of SCs is greatly influenced by various factors such as the reaction mechanism, crystal structure, and kinetics of electron/ion transfer in the electrodes, which have been challenging to address using previously investigated electrode materials like carbon and metal oxides/sulfides. Recently, tellurium and telluride-based materials have garnered increasing interest in energy storage technology owing to their high electronic conductivity, favorable crystal structure, and excellent volumetric capacity. This review provides a comprehensive understanding of the fundamental properties and energy storage performance of tellurium- and Te-based materials by introducing their physicochemical properties. First, we elaborate on the significance of tellurides. Next, the charge storage mechanism of functional telluride materials and important synthesis strategies are summarized. Then, research advancements in metal and carbon-based telluride materials, as well as the effectiveness of tellurides for SCs, were analyzed by emphasizing their essential properties and extensive advantages. Finally, the remaining challenges and prospects for improving the telluride-based supercapacitive performance are outlined.

Generation and Coupling of Radical Species from α-Alkoxy Bridgehead Carboxylic Acid, Selenide, Telluride, Acyl Selenide, and Acyl Telluride.

α-Alkoxy bridgehead radicals enable intermolecular construction of sterically congested C-C bonds due to their sterically accessible nature. We implemented these radical species into total syntheses of various densely oxygenated natural products and demonstrated their exceptional versatility. Herein, we employed different precursors to generate the same α-alkoxy bridgehead radical and compared the efficacy of the precursors for coupling reactions. Specifically, the bridgehead radical of the trioxaadamantane structure was formed from α-alkoxy carboxylic acid, selenide/telluride, and acyl selenide/acyl telluride, and reacted with 4-((tert-butyldimethylsilyl)oxy)cyclopent-2-en-1-one and 5-oxo-1-cyclopentene-1-carbonitrile. The efficiency of the bridgehead radical formation and subsequent coupling reaction significantly depended on the structures of the precursors and acceptors as well as the reaction conditions. Our findings provide new insights for selecting the appropriate substrates of key coupling reactions in the total synthesis of complex natural products.

Reveal Ultrafast Electron Relaxation across Sub-bands of Tellurium by Time- and Energy-Resolved Photoemission Microscopy.

Exploring ultrafast carrier dynamics is crucial for the materials' fundamental properties and device design. In this work, we employ time- and energy-resolved photoemission electron microscopy with tunable pump wavelengths from visible to near-infrared to reveal the ultrafast carrier dynamics of the elemental semiconductor tellurium. We find that two discrete sub-bands around the Γ point of the conduction band are involved in excited-state electron ultrafast relaxation and reveal that hot electrons first go through ultrafast intra sub-band cooling on a time scale of about 0.3 ps and then transfer from the higher sub-band to the lower one on a time scale of approximately 1 ps. Additionally, theoretical calculations reveal that the lower one has flat-band characteristics, possessing a large density of states and a long electron lifetime. Our work demonstrates that TR- and ER-PEEM with broad tunable pump wavelengths are powerful techniques in revealing the details of ultrafast carrier dynamics in time and energy domains.

Tunable Circular Photogalvanic and Photovoltaic Effect in 2D Tellurium with Different Chirality.

Chirality arises from the asymmetry of materials, where two counterparts are the mirror image of each other. The interaction between circular-polarized light and quantum materials is enhanced in chiral space groups due to the structural chirality. Tellurium (Te) possesses the simplest chiral crystal structure, with Te atoms covalently bonded into a spiral atomic chain (left- or right-handed) with a periodicity of 3. Here, we investigate the tunable circular photoelectric responses in 2D Te field-effect transistors with different chirality, including the longitudinal circular photogalvanic effect induced by the radial spin texture (electron-spin polarization parallel to the electron momentum direction) and the circular photovoltaic effect induced by the chiral crystal structure (helical Te atomic chains). Our work demonstrates the controllable manipulation of the chirality degree of freedom in materials.

LUMO-Mediated Se and HOMO-Mediated Te Nanozymes for Selective Redox Biocatalysis.

Selenium (Se) and tellurium (Te) nanomaterials with novel chain-like structures have attracted widespread interest owing to their intriguing properties. Unfortunately, the still-unclear catalytic mechanisms have severely limited the development of biocatalytic performance. In this work, we developed chitosan-coated Se nanozymes with a 23-fold higher antioxidative activity than Trolox and bovine serum albumin coated Te nanozymes with stronger prooxidative biocatalytic effects. Based on density functional theory calculations, we first propose that the Se nanozyme with Se/Se2- active centers favored reactive oxygen species (ROS) clearance via a LUMO-mediated mechanism, while the Te nanozyme with Te/Te4+ active centers promoted ROS production through a HOMO-mediated mechanism. Furthermore, biological experiments confirmed that the survival rate of γ-irritated mice treated with the Se nanozyme was maintained at 100% for 30 days by inhibiting oxidation. However, the Te nanozyme had the opposite biological effect via promoting radiation oxidation. The present work provides a new strategy for improving the catalytic activities of Se and Te nanozymes.

Tunable Chirality-Dependent Nonlinear Electrical Responses in 2D Tellurium.

Tellurium (Te) is an elemental semiconductor with a simple chiral crystal structure. Te in a two-dimensional (2D) form synthesized by a solution-based method shows excellent electrical, optical, and thermal properties. In this work, the chirality of hydrothermally grown 2D Te is identified and analyzed by hot sulfuric acid etching and high-angle tilted high-resolution scanning transmission electron microscopy. The gate-tunable nonlinear electrical responses, including the nonreciprocal electrical transport in the longitudinal direction and the nonlinear planar Hall effect in the transverse direction, are observed in 2D Te under a magnetic field. Moreover, the nonlinear electrical responses have opposite signs in left- and right-handed 2D Te due to the opposite spin polarizations ensured by the chiral symmetry. The fundamental relationship between the spin-orbit coupling and the crystal symmetry in two enantiomers provides a viable platform for realizing chirality-based electronic devices by introducing the degree of freedom of chirality into electron transport.

Following the Trace of Cyclodextrins on the Selenium and Tellurium Odyssey.

There is an urgent need to develop safer and more effective modalities for the treatment of numerous pathologies due to the increasing rates of drug resistance, undesired side effects, poor clinical outcomes, etc. Over the past decades, cyclodextrins (CDs) have gathered great attention as potential drug carriers due to their ability to enhance their bioactivities and properties. Likewise, selenium (Se) and tellurium (Te) have been extensively studied during the last decades due to their possible therapeutical applications. Although there is limited research on the relationship between Se and Te and CDs, herein, we highlight different representative examples of the advances related to this topic as well as give our view on the future directions of this emerging area of research. This review encompasses three different aspects of this relationship: (1) modification of the structure of the different CDs; (2) formation of host-guest interaction complexes of naïve CDs with Se and Te derivatives in order to overcome specific limitations of the latter; and (3) the use of CDs as catalysts to achieve novel Se and Te compounds.

Theoretical Design of Tellurium-Based Two-Dimensional Perovskite Photovoltaic Materials.

In recent years, the photoelectric conversion efficiency of three-dimensional (3D) perovskites has seen significant improvements. However, the commercial application of 3D perovskites is hindered by stability issues and the toxicity of lead. Two-dimensional (2D) perovskites exhibit good stability but suffer from low efficiency. Designing efficient and stable lead-free 2D perovskite materials remains a crucial unsolved scientific challenge. This study, through structural prediction combined with first-principles calculations, successfully predicts a 2D perovskite, CsTeI5. Theoretical calculations indicate that this compound possesses excellent stability and a theoretical efficiency of up to 29.3%, showing promise for successful application in thin-film solar cells. This research provides a new perspective for the design of efficient and stable lead-free 2D perovskites.

Unlocking Four-electron Conversion in Tellurium Cathodes for Advanced Magnesium-based Dual-ion Batteries.

Magnesium (Mg) batteries hold promise as a large-scale energy storage solution, but their progress has been hindered by the lack of high-performance cathodes. Here, we address this challenge by unlocking the reversible four-electron Te0/Te4+ conversion in elemental Te, enabling the demonstration of superior Mg//Te dual-ion batteries. Specifically, the classic magnesium aluminum chloride complex (MACC) electrolyte is tailored by introducing Mg bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2), which initiates the Te0/Te4+ conversion with two distinct charge-storage steps. Te cathode undergoes Te/TeCl4 conversion involving Cl- as charge carriers, during which a tellurium subchloride phase is presented as an intermediate. Significantly, the Te cathode achieves a high specific capacity of 543 mAh gTe -1 and an outstanding energy density of 850 Wh kgTe -1, outperforming most of the previously reported cathodes. Our electrolyte analysis indicates that the addition of Mg(TFSI)2 reduces the overall ion-molecule interaction and mitigates the strength of ion-solvent aggregation within the MACC electrolyte, which implies the facilized Cl- dissociation from the electrolyte. Besides, Mg(TFSI)2 is verified as an essential buffer to mitigate the corrosion and passivation of Mg anodes caused by the consumption of the electrolyte MgCl2 in Mg//Te dual-ion cells. These findings provide crucial insights into the development of advanced Mg-based dual-ion batteries.