Te Nanowires Research Articles

Phase Change Ge-Rich Ge-Sb-Te/Sb2Te3 Core-Shell Nanowires by Metal Organic Chemical Vapor Deposition.

Ge-rich Ge–Sb–Te compounds are attractive materials for future phase change memories due to their greater crystallization temperature as it provides a wide range of applications. Herein, we report the self-assembled Ge-rich Ge–Sb–Te/Sb2Te3 core-shell nanowires grown by metal-organic chemical vapor deposition. The core Ge-rich Ge–Sb–Te nanowires were self-assembled through the vapor–liquid–solid mechanism, catalyzed by Au nanoparticles on Si (100) and SiO2/Si substrates; conformal overgrowth of the Sb2Te3 shell was subsequently performed at room temperature to realize the core-shell heterostructures. Both Ge-rich Ge–Sb–Te core and Ge-rich Ge–Sb–Te/Sb2Te3 core-shell nanowires were extensively characterized by means of scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Raman microspectroscopy, and electron energy loss spectroscopy to analyze the surface morphology, crystalline structure, vibrational properties, and elemental composition.

Super-assembled atomic Ir catalysts on Te substrates with synergistic catalytic capability for Li-CO2 batteries

Rechargeable Li-CO2 batteries (LCBs) are considered as a promising candidate for the next generation energy storage system, but still be impeded by the lack of high-performance cathode catalyst and poor understanding for the complicated reaction mechanism. In the present work, we demonstrate that the catalytic capability of cathode catalyst of LCBs can be remarkably enhanced from the accelerated reaction kinetics using a p-type substrate as adsorption/desorption promoter for refined reaction route. A carbon-free atomic Ir-Te cathode catalyst with Ir atomic cluster is uniformly super-assembled on the surface of Te nanowires forming an amorphous surface layer (ca. 3 nm) to maximize the catalytic capability of active Ir sites and provide a refined reaction pathway due to synergistic effect of Ir active sites and Te substrate. The adsorption ability of Li2C2O4 during discharging and the desorption ability of CO2 species during charging of the p-type Te substrate could both promote the catalytic reaction kinetics and optimize the reaction pathways on Ir active sites. Finally, a large specific capacity of 13,247.1 mAh g−1 and an excellent high rate cyclability with stably over 350 and 200 cycles at the current density of 1000 and 2000 mA g−1 are achieved. This contribution provides a rational design strategy for high performance cathode catalyst, and intrinsic insight towards the understanding the reaction mechanisms of LCBs.

Core-shell Au@PtIr nanowires with dendritic alloy shells as efficient bifunctional catalysts toward methanol oxidation and hydrogen evolution reactions

Nanocatalysts with combination of unique morphologies and synergistic interactions have a potential to enhance electrocatalytic ability related to the reactions in fuel cells. Here, we show a wet-chemistry-based synthesis of dendritic Au@PtIr nanowires (NWs) with core-shell constructions regarding Te NWs as sacrificial templates for methanol oxidation reaction (MOR) and hydrogen evolution reaction (HER). Regarding the synthesis of Au@PtIr NWs, Au NWs are firstly obtained through galvanic replacement with Te templates, followed by growth of alloy PtIr shells in subsequent seed-mediated growth. The as-synthesized core-shell Au@PtIr nanowires combine the advantage of one-dimensional (1D) dendritic feature that facilitate fast electron transport and provide more interfaces and interstices between catalytic active sites and electrolyte, with the synergistic interactions in alloy shells. Consequently, the as-prepared Au@PtIr NWs show good catalytic properties in MOR and HER in terms of higher activity, larger electrochemically active surface areas (ECSAs) and better anti-toxicity than commercial Pt/C.

Study on the electronic properties of M6X6 (M = Mo, W; X = S, Se, Te) nanowire arrays

The stability of M6X6 (M = Mo, W; X = S, Se, Te) nanowire arrays was investigated with different displacements and rotation angles (α, β) by first-principles calculations. Among the four arrays (including square, centered square, hexagonal I, and hexagonal II), the hexagon I array having α = 15° is most stable. Interestingly, by arranging the nanowires into such an array, we found that the isolated M6X6 (X = Te) nanowires could be transformed from semiconductor to metal by coupling between individual nanowires, while the isolated M6X6 (X = S, Se) nanowires kept the original metallic nature unchanged.

Directly grown Te nanowire electrodes and soft plasma etching for high-performance MoTe2 field-effect transistors

Contact tailoring for two-dimensional (2D) transition metal dichalcogenides (TMDs) to achieve high-performance devices remains a challenge. Fermi-level pinning at 2D TMD–metal contacts leads to a Schottky barrier for contacts. In addition, when there are no dangling bonds between 2D TMDs and contacts, the contact resistance increases. In this study, Te nanowire (NW) contacts were employed for a MoTe2 p-channel of enhancement mode field-effect transistor (FET). The Te NWs were directly grown on 2D MoTe2 film by metal–organic chemical vapor deposition and selectively etched by a soft plasma etching technique for contact isolation. Using t-Te NW contacts on three-atomic-layer MoTe2, a highly effective field-effect mobility of 543.9 cm2/Vs, as well as ohmic contacts and atomic hybridization, was achieved. These results of t-Te NW electrodes provide a novel device structure for p-type 2D TMD transistors with excellent performances. Further, they offer a practical guideline for wafer-scale 2D TMD-based high-performance electronics and optoelectronics.

Near‐Infrared Light Triggered Self‐Powered Mechano‐Optical Communication System using Wearable Photodetector Textile

AbstractThe merging of humans and machines depends on the contact sensor medium used. However, this contact interaction inevitably leads to mechanical loss. Photodetectors are cutting‐edge tools in optical communication that use controlled lighting to achieve efficient signal conversion to drive mechano–optical communication systems and provide an innovative interface for the Internet of Things services. Here, a self‐powered, non‐contact mechano–optical communication system based on a wearable Te@TeSe photodetector textile is presented, which encodes near‐infrared light to modulate robotic manipulator actions. The wearable Te@TeSe photodetector textile enhanced the photocurrent and responsivity by 400 times compared to a pristine Te nanowire (NW) array. The type II heterojunction of Te@TeSe NWs is proved by first‐principles calculations and simulated, providing insights on photogenic carrier transmission in Te@TeSe NWs. This system shows the possibility of duplicate real‐time execution of mechanical gestures in virtual environments and paves the way for advanced optical devices applied to information transmission and mechano–optical communication.

Tellurium nanowires wrapped by surface oxidized tin disulfide nanosheets achieves efficient photocatalytic reduction of U(VI)

Surface and interface engineering represents a powerful strategy for photocatalytic reduction of soluble hexavalent uranium (U(VI)) into insoluble tetravalent uranium (U(IV)). Herein, we fabricated surface oxidized tin disulfide nanosheets (O-SnS2) on tellurium nanowires (Te@O-SnS2) as highly efficient and stable photocatalysts for U(VI) removal from wastewater. In this system, the Te nanowires increased the surface negative charge and resulted in the injection of hot electrons into O-SnS2 nanosheets, which facilitated the binding and reduction of U(VI) on the abundant surface defects of O-SnS2. Under the irradiation of simulated sunlight, the removal efficiency toward U(VI) by Te@O-SnS2 reached 97.3% in 60 min with the initial U(VI) concentration of 8 mg/L. Additionally, the maximum extraction capacity of U(VI) by Te@O-SnS2 reached 704.8 mg/g at the initial U(VI) concentration of 200 mg/L. Furthermore, the Te@O-SnS2 exhibited remarkable resistence ability for the interfering ions and a U(VI) removal efficiency > 88.4% over a wide range of pH, and maintained a high U(VI) removal efficiency (>92%) during cycle tests at pH 4.8.

(Keynote) All Roads Lead to Rome: Paths of Heat and Charge Transport in Hybrid Polymer-Nanowire Systems

In this talk, we present research that aims to identify the specific pathways of heat and charge transport in complex hybrid polymer-nanowire thermoelectric systems. These materials have demonstrated remarkable performance due to interfacial charge transport dynamics that have proven difficult to untangle. Here I present the work of a few recent papers to disaggregate the role of the organic and inorganic layer in the transport of charge and heat, as well as the mechanism that causes an enhancement in thermoelectric performance. We also assess the role of specific features of the polymer and nanowire themselves, and how those contribute to transport. We do this at both the single nanowire level, and also at the film level, enabling meaningful comparisons and conclusions. Through combining thermoelectric property measurements using a custom-built suspended microbridge setup for single nanowires, the Kang-Snyder charge transport model as well as gate modulated electrical conductivity measurements, we conclude that the thin organic PEDOT:PSS shell is the predominant channel for charge carrier transport in this hybrid material, and the large electrical conductivity is attributed to the highly ordered PEDOT chains on the Te nanowire surface brought about by a templating effect. We also present complementary research on charge transport characteristics of modified PEDOT:PSS derivatives as well. This talk will summarize the work of our 4 most recent manuscripts from the last few months.

A high performance flexible and robust printed thermoelectric generator based on hybridized Te nanowires with PEDOT:PSS

In this work, we demonstrate a water-based scalable synthetic method of Te nanowires (NWs) and formulation of hybrid thermoelectric (TE) inks utilizing poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), towards the fabrication of high performance and flexible printed thermoelectric generators (TEGs). X-Ray diffraction (XRD) and Raman spectra confirm the high crystallinity of Te NWs nanocrystals with hexagonal lattice. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) illustrated the microstructural features of the produced nanostructures, as well as the monocrystalline nature of the synthesized Te NWs. Hall-effect measurements determined the carrier density and mobility of Te NWs and their hybrid materials. According to the thermoelectric response and best power factor (PF) of the hybrid inks measured in solid-state of pre-fabricated films (max. PF = 102.42 μW/m K2), a flexible TEG has been fabricated with a power output (Pout) of ~ 4.5 µW upon being exposed to ΔT = 100 K. The fabricated TEG demonstrated herein can be produced in a continuous and scalable roll-to-roll (R2R) printing process using i.e. slot die, gravure, etc. printing technologies towards the realization of large scale flexible TEG production and future large scale thermal energy harvesting by printed TEG devices.

Gate‐Tunable Photodiodes Based on Mixed‐Dimensional Te/MoTe2 Van der Waals Heterojunctions

AbstractThe dangling‐bond‐free surfaces of 2D materials enable them to possess various degrees of freedom to form heterostructures with non‐2D materials. This allows for the combination of the advantages of different dimensional materials to fabricate van der Waals (vdW) heterostructures, thereby improving device performance and even bringing diversity and novelty. Herein, a mixed‐dimensional vdW heterostructure photodiode comprising a 1D tellurium (Te) nanowire and a 2D molybdenum ditelluride (MoTe2) flake is demonstrated. Forward rectifying and backward rectifying characteristics are realized by applying different gate voltage. The device displays a broad spectral response from visible to near‐infrared and exhibits ultrahigh external quantum efficiency of 7.16 × 103% for photogating effect. Moreover, the response time can be improved by controlling gate voltage and a rapid response time of 4.8 ms is achieved. These mixed‐dimensional vdW heterojunctions, which take advantages of both 1D and 2D semiconductors, will facilitate the development of next‐generation electronics and optoelectronics.

Fabrication of 1D Te/2D ReS2 Mixed-Dimensional van der Waals p-n Heterojunction for High-Performance Phototransistor.

The superior optical and electronic properties of the two-dimensional (2D) rhenium disulfide (ReS2) makes it suitable for nanoelectronic and optoelectronic applications. However, the internal defects coupled with with the low mobility and light-absorbing capability of ReS2 impede its utilization in high-performance photodetectors. Fabrication of mixed-dimensional heterojunctions is an alternative method for designing high-performance hybrid photodetectors. This study proposes a mixed-dimensional van der Waals (vdW) heterojunction photodetector, containing high-performance one-dimensional (1D) p-type tellurium (Te) and 2D n-type ReS2, developed by depositing Te nanowires on ReS2 nanoflake using the dry transfer method. It can improve the injection and separation efficiency of photoexcited electron-hole pairs due to the type II p-n heterojunction formed at the ReS2 and Te interface. The proposed heterojunction device is sensitive to visible-light sensitivity (632 nm) with an ultrafast photoresponse (5 ms), high responsivity (180 A/W), and specific detectivity (109), which is superior to the pristine Te and ReS2 photodetectors. As compared to the ReS2 device, the responsivity and response speed is better by an order of magnitude. These results demonstrate the fabrication and application potential of Te/ReS2 mixed-dimensional heterojunction for high-performance optoelectronic devices and sensors.

Designing complex radial heterostructures of Te/Bi2Te3 and Te/Bi2-x Pb x Te3 nanowires: fundamental mechanistic insights into nanowire growth and evolution

Metal telluride/Te heterostructure nanowires are important thermoelectric materials and it is important to be able to tune these materials according to the requirement of the application. In order to do so, a good understanding of the reaction mechanism and critical observation of the evolution of the nanowire heterostructure during the course of reaction is essential. Here, single crystalline, anisotropic Te core/Bi2Te3 shell nanowires have been synthesized by a facile template-based wet chemical synthesis method. The formation and evolution mechanism of the heterostructure has been elucidated by several control reactions, detailed transmission electron microscopy imaging and composition analysis using energy dispersive spectroscopy in scanning transmission electron microscopy mode of the products of the reactions. Fundamental understanding of the formation mechanism and time-dependent evolution of the core–shell structure in the nanowire have led to successful designing of higher order heterostructures involving Te/Bi2-x Pb x Te3. Through this study, interesting insights into the crystal structure evolution, crystal growth and miscibility of PbTe and Bi2Te3 into each other is obtained.

In-Plane Oriented Linear Assembly of Te Nanowires in Polydimethylsiloxane-Based Composite Film for the Enhancement of Piezoelectric Property

Flexible piezoelectric materials are attractive as empowering devices in the field of sensors, actuators and energy harvesting. Herein, we fabricate a polymer-based nanocomposite with piezoelectric property by incorporation of tellurium (Te) nanowires. Firstly, large-scale selective synthesis of uniform single crystalline tellurium nanowires with a diameter of 150 nm av. and 10 μm av. in length, can be realized by a hydrothermal process. The Te nanowires with random distribution in pre-polymer of polydimethylsiloxane (PDMS) is relocated forming linearly aligned assembly controlled by application of external AC electric field. The aligned Te-PDMS at 0.5 wt% Te content gives a maximum output voltage of 13.9 V, which is 2.4-fold comparing corresponding film with random distribution. This work provides an effective alignment of nanofillers in a viscous polymer matrix and noble method to fabricate enhance piezoelectric composite film materials.

Identification of a TeO32- reductase/mycothione reductase from Rhodococcus erythropolis PR4.

A Rhodococcus erythropolis bacterium that tolerates normally lethal concentrations of Fe(II), Cu(II), AsO32-, SeO32-, TeO32-, Cd(II) and Zn(II) was identified from an environmental isolate. In characterizing the molecular basis for metal tolerance, a mycothione reductase (Mtr) with remarkable selectivity for TeO32- reduction over SeO32- was identified. In equimolar concentrations of TeO32- and SeO32-, the enzymatic product contains a 7-fold excess of Te. This selectivity is remarkable because the standard reduction potential of SeO32- is 0.20V more favorable for reduction than TeO32. Selectivity of the enzyme for TeO32- decreases with increasing assay pH. Homology modeling of the enzyme identifies four aromatic residues near the active site, including two histidine residues, that are not present in a related SeO32- preferring reductase. On the basis of more favorable π-interactions for Te than for Se and the pH dependence of the selectivity, the Te-selectivity is attributed in part to these aromatic residues. The resulting Te0 enzymatic product resembles Te nanowires.

Giant and Anisotropic Nonlinear Optical Responses of 1D van der Waals Material Tellurium

AbstractRecently, tellurium (Te), composed of helical Te chains stacked via the van der Waals interaction, emerges as a versatile material with high carrier mobilities and intriguing topological properties. Here, it is revealed that Te's 1D counterpart, that is, Te nanowire (NW), has advantages over the NWs of other materials in the characteristics of giant and anisotropic nonlinear optical responses. This endows the Te NW with potentials for developing nonlinear photonic and optoelectronic nanodevices with high efficiency and polarization selectivity. Compared with the well‐studied III–V and II–VI compound NWs, such as aluminium gallium arsenide, zinc oxide, and indium phosphide NWs, second harmonic generations (SHGs) and third harmonic generations (THGs) from the Te NWs are more than two orders of magnitude stronger. Its second‐order nonlinear susceptibility is estimated as 1.25 × 104 pm V−1, which is the highest value in the reported NWs, and almost four orders of magnitude higher than ZnO NW. Further, this giant optical nonlinearity promises the realizations of strong SHGs and sum‐frequency generations from Te NWs with the pump of sub‐milliwatt continuous‐wave lasers. Determined by the helical Te chain, its SHG only responds to the pump laser polarized perpendicularly to the long axis of NW, which is opposite to the polarization dependencies in other NWs, and the THG has a distorted fourfold polarimetric pattern.

Morphology and property tuning of Te nanostructures in a hydrothermal growth

Te nanoplates, nanowires, and nanospheres were successfully synthesized by a hydrothermal method with glucose as a surfactant agent. By simply changing the reaction time, the morphology of Te nanostructures can be changed from nanoplates, to nanowires, and ultimately to nanospheres. The samples were studied by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, x-ray photoemission spectroscopy, and photoluminescence measurements. It is found that the reaction time plays an important role in morphology formation and optical properties of Te nanostructures. A possible growth mechanism involving a self-assembly process and Wulff facets theorem is proposed to explain the formation of Te nanoplates, nanowires, and nanospheres. This study presents a simple way to control the morphology of Te nanostructures and their optical properties.

Parallel Nanoimprint Forming of One-Dimensional Chiral Semiconductor for Strain-Engineered Optical Properties

HighlightsExquisite strain engineering in 1D chiral semiconductor.Facile nanoimprinting induced tensile strain in Te nanowire.Intriguing and tunable optical properties of 1D Te nanowire by strain engineering.

Polarization and magneto-optical properties of excitonic emission from wurtzite CdTe/(Cd,Mg)Te core/shell nanowires

Wurtzite CdTe and (Cd,Mn)Te nanowires embedded in (Cd,Mg)Te shells are grown by employing vapour–liquid–solid growth mechanism in a system for molecular beam epitaxy. A combined study involving cathodoluminescence, transmission electron microscopy and micro-photoluminescence is used to correlate optical and structural properties in these structures. Typical features of excitonic emission from individual wurtzite nanowires are highlighted including the emission energy of 1.65 eV, polarization properties and the appearance B-exciton related emission at high excitation densities. Angle dependent magneto-optical study performed on individual (Cd,Mn)Te nanowires reveals heavy-hole-like character of A-excitons typical for wurtzite structure and allows to determine the crystal field splitting, ΔCR. The impact of the strain originating from the lattice mismatched shell is discussed and supported by theoretical calculations.

Nanocable catalysts MTe (M = Pt, PtCu)@UIO-67 for CO2 conversion

Zr-based metal–organic framework nanocable catalysts comprising MTe(M = Pt, PtCu)@UIO-67 resembling “sugarcoated haws on a stick” were assembled. Ultrathin Te nanowires with diameters of about 8.48 nm served as a sacrificial template for the epitaxial growth of an outer M (Pt or PtCu) to obtain cable cores comprising MTe nanowires with good dispersity, which were then successfully encapsulated in the center of a monodisperse MTe@UIO-67 cable nano-structured catalyst. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and energy dispersive X-ray (EDX) element mapping were used to investigate the morphology, structure and composition of the nanocable catalysts. Six types of catalysts were synthesized, and all of the catalysts demonstrated superior product selectivity to CO for reverse water-gas shift (RWGS) reaction. Especially, the morphology and dispersion of PtCuTe@UIO-67 nanocable catalyst can be maintained to some extent after catalysis at high temperature, and PtTe@UIO-67 catalyzed CO2 conversion was achieved with 99.86% CO selectivity.

Boosted charge transfer and Na-ion diffusion in cooling-fins-like Sb2Te3–Te nano-heterostructure for long cycle life and high rate capability anode

To improve the electronic conductivity and accelerate the Na-ion diffusion in active materials for sodium-ion batteries (SIBs), Sb2Te3–Te nano-heterostructure (STNH) electrodes are constructed based on the hierarchical nanostructures of two-dimensional (2D) Sb2Te3 nanoblades serialized by one-dimensional (1D) Te nanowires for high-performance anode material. The STNH electrode delivered high sodium storage capacity of 375 mAh g−1 at 100 mA g−1 after 200 cycles and provided a capacity of 226 mAh g−1 at 15 A g−1, even could obtain a high capacity of 365 mAh g−1 at 1.5 A g−1 after 1000 cycles, respectively. The sodiation/desodiation reaction mechanism is also investigated by ex-situ selected-area electron diffraction (SAED) and in situ X-ray diffraction (XRD). The enhanced sodium storage properties of STNH are mainly attributed to the integrated merits of both 1D and 2D with enhanced charge carrier migration and good structure stability. This work gives the rational guidance to design novel hierarchical nanostructures integrating 1D and 2D nano-heterojunction materials for advanced battery materials. The as-designed STNH electrode enhancing sodium storage exhibts potential interest in SIBs.