Tellurium Nanowires Research Articles

Toward a Procedure for the Template Free Growth of Te Nanowires Across an Insulator by Electrodeposition.

In this work, we present a method for direct, site-selective growth of tellurium nanowires by electrochemical deposition. The Te nanowires were grown laterally between two specially designed nanoband electrodes across a gap, and over a dielectric material, forming a lateral device structure directly. The resulting wires are crystalline and phase pure, as evidenced by Raman spectroscopy, EDS (energy dispersive X-ray spectroscopy), and ADF-STEM (annular dark field scanning transmission electron microscopy). The precise conditions for lateral growth of the nanowires were investigated and the fabrication of an electronic device from the as-deposited material, without the need for any transfer process or further contact fabrication, is demonstrated.

Large-Scale Green Method for Synthesizing Ultralong Uniform Tellurium Nanowires for Semiconductor Devices.

This study presents a large-scale green approach for synthesizing ultralong tellurium nanowires with diameters around 13 nm using a solution-based method. By adjusting key synthesis parameters such as the surfactant concentration, temperature, and reaction duration, we achieved high-quality, ultralong Te NWs. These nanowires exhibit properties suitable for use in semiconductor applications, particularly when employed as channel materials in thin-film transistors, displaying a pronounced gate effect with a high switch of up to 104 and a mobility of 0.9 cm2 V-1s-1. This study underscores the potential of solvent-based methods in synthesizing large-scale ultralong Te NWs as a critical resource for future sustainable nanoelectronic devices.

Inkjet-printed p-type tellurene and n-type MoS2 transistors for CMOS electronics

Abstract Two-dimensional semiconductor materials combine exceptional electronic transport properties with mechanical flexibility and hence can be an ideal choice for large-area flexible and wearable electronics. While inkjet printing may be a suitable approach to fabricate high throughput electronic components on polymer substrates, solution-processed 2D semiconductor network transistors suffer from two major hindrances: extremely high inter-flake resistance and the lack of high-performance p-type semiconductors. This study shows that inkjet-printed tellurium nanowires or tellurene nanoflakes can offer high-performance p-type TFTs with current density up to 100 μA/μm and an On-Off ratio >105. In order to circumvent the high inter-flake junction resistance, a narrow-channel, near-vertical device architecture has been used that ensures predominantly intra-flake/ intra-nanowire transport, which resulted in three orders of magnitude increase in the current density compared to conventional devices without compromising on the On-Off ratio. Moreover, we show the whole device operation within ± 2 V, with a threshold voltage close to 0 V. The complete device fabrication is carried out at room temperature, thereby making it compatible with inexpensive polymer substrates. Next, outstanding device performance has also been realized with electrochemically-exfoliated and inkjet-printed n-type MoS2 TFTs, demonstrating a current density of 60 μA/μm and an On-Off ratio of 106. Furthermore, we show tellurene-based p-type depletion-load unipolar inverters and CMOS inverters alongside n-type MoS2 TFTs, demonstrating a signal gain of 12 and 11, respectively. The CMOS inverters are found to operate at a frequency of 1 kHz.

Thermoelectric Property Enhancement of Tellurium Nanowires by Surface Passivation.

The pursuit of high-performance thermoelectric materials is of paramount importance in addressing energy sustainability and environmental concerns. Here, we explore the multifaceted impact of sulfur passivation in the matrix of tellurium nanowires (TeNWs), encompassing environmental control, thermoelectric properties, and charge carrier mobility. In this study, we present the facile production of TeNWs using an aqueous solution synthesis approach. The synthesized TeNWs were subsequently subjected to surface modification involving sulfur moieties. Our findings demonstrate that sulfur passivation not only effectively safeguards the nanowires from environmental degradation but also significantly augments their thermoelectric properties. Notably, the highest recorded values were achieved at 560 K for passivated tellurium nanowires, exhibiting a Seebeck coefficient of 246 μV/K, an electrical conductivity of 14.2 S/cm, and power factors of 86.7 μW/m-K2. This strategy presents a promising avenue for the development of advanced thermoelectric materials for applications in energy harvesting, waste heat recovery, and sustainable energy conversion technologies.

Oxidation Control to Augment Interfacial Charge Transport in Te-P3HT Hybrid Materials for High Thermoelectric Performance.

Organic-inorganic hybrid thermoelectric (TE) materials have attracted tremendous interest for harvesting waste heat energy. Due to their mechanical flexibility, inorganic-organic hybrid TE materials are considered to be promising candidates for flexible energy harvesting devices. In this work, enhanced TE properties of Tellurium (Te) nanowires (NWs)- poly (3-hexylthiophene-2, 5-diyl) (P3HT) hybrid materials are reported by improving the charge transport at interfacial layer mediated via controlled oxidation. A power factor of ≈9.8µW(mK2)-1 is obtained at room temperature for oxidized P3HT-TeNWs hybrid materials, which increases to ≈64.8µW(mK2)-1 upon control of TeNWs oxidation. This value is sevenfold higher compared to P3HT-TeNWs-based hybrid materials reported in the literature. MD simulation reveals that oxidation-free TeNWs demonstrate better templating for P3HT polymer compared to oxidized TeNWs. The Kang-Snyder model is used to study the charge transport in these hybrid materials. A large σE0 value is obtained which is related to better templating of P3HT on oxygen-free TeNWs. This work provides evidence that oxidation control of TeNWs is critical for better interface-driven charge transport, which enhances the thermoelectric properties of TeNWs-P3HT hybrid materials. This work provides a new avenue to improve the thermoelectric properties of a new class of hybrid thermoelectric materials.

Wet Spun Composite Fiber with an Ordered Arrangement of PEDOT:PSS‐Coated Te Nanowires for High‐Performance Wearable Thermoelectric Generator

AbstractThermoelectric (TE) fibers are more suitable than films for portable or wearable devices. Herein, 2–3 nm thick poly (3,4‐ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) layer‐coated tellurium nanowires (PC‐Te NWs) are in situ prepared by a hydrothermal method. Then a series of PEDOT: PSS/PC‐Te NWs composite fibers are prepared by wet spinning and post‐treatment. The nanolayer prevents the agglomeration of the Te NWs and makes the NWs and PEDOT:PSS matrix have good compatibility, which results in the PC‐Te NWs content to a high value of 70 wt% and the fibers still with flexibility. The high aspect ratio of the PC‐Te NWs and the stress from the inner wall of the needle during spinning make the NWs ordered align along the composite fiber. Due to the large content and orientational arrangement of the PC‐Te NWs, as well as effective post‐treatment, an optimized composite fiber shows a power factor of 385.4 µW m−1 K−2 at 300 K, which is ≈4.9 times as high as the highest value of previously reported PEDOT:PSS/Te NWs‐based composite fibers. In addition, the composite fiber has good flexibility. The flexible TE generators assembled have excellent output performance. This work provides an effective strategy for the preparation of high‐performance flexible TE composite fibers.

Biomimetic array actuators for multisituation low-grade energy harvesting

Low-grade energy resources are abundant and widely available, yet efficiently harnessing and continuously collecting this energy presents a considerable challenge, leading to significant energy losses. In this work, we introduce a biomimetic array actuator constructed with a sodium alginate (SA)-tellurium nanowires (Te NWs)/polyvinylidene fluoride (PVDF) bilayer structure that responds to various stimuli such as low temperature, natural light, and humidity. Significantly, this actuator generates autonomous self-oscillatory motion driven by an internal mechanical feedback loop. Utilizing its high-frequency self-oscillating motion, this actuator efficiently harnesses low-grade energy sources, including waste heat, non-concentrated sunlight, and exhaust steam. Under various driving conditions, including a 60 °C heater, natural light, and 70 °C steam, the 3 × 3 array actuators can generate peak voltages of 1.5 V, 2 V, and 4 V, respectively. This research has the potential to unlock opportunities for a range of low-grade energy harvesting technologies utilizing flexible actuators.

Biomimetic wafer-scale alignment of tellurium nanowires for high-mobility flexible and stretchable electronics.

Flexible and stretchable thin-film transistors (TFTs) are crucial in skin-like electronics for wearable and implantable applications. Such electronics are usually constrained in performance owing to a lack of high-mobility and stretchable semiconducting channels. Tellurium, a rising semiconductor with superior charge carrier mobilities, has been limited by its intrinsic brittleness and anisotropy. Here, we achieve highly oriented arrays of tellurium nanowires (TeNWs) on various substrates with wafer-scale scalability by a facile lock-and-shear strategy. Such an assembly approach mimics the alignment process of the trailing tentacles of a swimming jellyfish. We further apply these TeNW arrays in high-mobility TFTs and logic gates with improved flexibility and stretchability. More specifically, mobilities over 100 square centimeters per volt per second and on/off ratios of ~104 are achieved in TeNW-TFTs. The TeNW-TFTs on polyethylene terephthalate can sustain an omnidirectional bending strain of 1.3% for more than 1000 cycles. Furthermore, TeNW-TFTs on an elastomeric substrate can withstand a unidirectional strain of 40% with no performance degradation.

Performance potential of transistors based on tellurium nanowire arrays: A quantum transport study

Low-dimensional nanomaterials provide promising material platforms for aggressively scaled transistor technologies. We assess the performance potential of transistors based on an array of Tellurium nanowires (TNWs), by parameterizing a machine-learning (ML) tight-binding model with quantum transport device simulations. It has been shown that a transistor based on a parallel array of carbon nanotubes (CNTs) can have excellent on-state performance, but the small bandgap limits the transistor scalability and off-state performance. Our results indicate that compared to the CNT array FETs, the TNW array FETs have significantly suppressed ambipolar transport and improved subthreshold characteristics. The TNW array FET has the potential to achieve a near-ideal subthreshold swing (SS) close to 60 mV/dec, a very large on–off ratio (>109), and low source-drain leakage current at a 10 nm-scale channel length, due to its excellent gate electrostatics with a gate-all-around (GAA) structure, larger band gap and reduced quantum–mechanical tunneling. The TNW array FET also shows excellent scalability with a SS below 100 mV/dec when the channel length is further scaled down to 5 nm. Its larger bandgap and heavier effective mass significantly reduce quantum tunneling. This mechanism contributes to improved subthreshold and lower leakage but also highlights the need to develop low Schottky barrier contacts for TNWs.

Photonic and phononic properties of oriented 5 nm diameter tellurium nanowires

We study polarized optical absorption and Raman spectra (OAS and RS) of ∼5 nm diameter tellurium (Te) nanowires (NWs) confined in chrysotile asbestos nanotubes packed parallel to each other into nearly-perfect-hexagonal lattice. Te was encapsulated into the nanotubes from molt using ∼20 kbar pressure. Asbestos with Te NWs (asb-Te) shows a high OAS/RS anisotropy due to a strong NW-light interaction for the light polarized papallel to NWs (E//c) and a weak one for the light polarized perpendicular to NWs. Importantly, asb-Te RS display bands of confined acoustic phonons at ∼9 cm−1 and ∼23 cm−1, specific signatures of 5 nm diameter Te NWs. Density-functional-theory calculation shows agreement with the observed frequencies and flattening of NW acoustic phonon dispersions useful for thermo-electricity. Asb-Te optical phonon A1-mode Raman band displays frequency upshift compared to the bulk-Te band due to enhancement of the intrachain bonds on expense of interchain ones. Asb-Te 2nd-order RS confirm this. Surprisingly, E-modes display LO-phonon RS-activity in asb-Te instead of TO-phonon-activity in bulk-Te. We observe enhancement of the NW Raman signal compared to that of bulk Te, which is associated with the Mie-resonance-induced NW-light interaction enhancement for E//c, which is important for photonic and photo-electric applications.

Van der waals epitaxial growth of mixed-dimensional 1D/2D heterostructures with tellurium nanowires and transition metal dichalcogenide nanosheets for nonlinear optical applications

One-dimensional (1D) tellurium (Te) nanowires (NWs) have triggered intense attention due to their remarkable properties in electronics, optoelectronics and nonlinear optics. However, the saturable absorption properties of Te NWs and the ability to be bleached by strong pulsed energy need to be further improved. Van der Waals (vdW) heterostructures based on two-dimensional (2D) transition metal dichalcogenides (TMDCs) exhibit prominent nonlinear optical properties. Direct epitaxial growth of large-area 1D/2D Te-TMDC vdW heterostructures is still rarely investigated. Herein, we demonstrate the controllable epitaxial growth of large-scale 1D/2D vertical Te-TMDC heterostructures via two-step vapor phase deposition method. Our experimental results have confirmed that the saturable absorption properties of as-prepared Te-TMDC heterostructures can be obviously enhanced. The first principle calculations and surface potential measurements demonstrate that effective interlayer charge transfer between Te NWs and TMDC nanosheets is beneficial for promoting the saturable absorption properties. Systematic investigation of vdW Te-TMDC heterostructures with nonlinear optical properties is vital for the next generation of nanophotonics and integrated photonics, which paves the way for the development of saturable absorbers and light modulators based on Te-TMDC vdW heterostructures.

Triboelectric Nanosensor Integrated with Robotic Platform for Self-Powered Detection of Chemical Analytes

Rapid on-site detection of hazardous chemicals is imperative for remote security and environmental monitoring applications. However, the implementation of current sensing technologies in real environments is limited due to an external high-power requirement, poor selectivity and sensitivity. Recent progress in triboelectric nanosensors and nanogenerators presents tremendous opportunities to address these issues. Here, we report an innovative self-powered triboelectric nanosensor for detection of Hg2+ ions, a harmful chemical pollutant, in a rapid single step on-site detection mechanism. Based on the mechanism of solid-liquid contact electrification, tellurium nanowire (Te NW) arrays serving as a solid triboelectric material as well as the sensing probe underwent periodic contact and separation with the Hg2+ solution, leading to the in situ formation of mercury telluride nanowire (HgTe NWs) owing to the selective binding affinity of Te NWs toward Hg2+ ions. To realize the on-site sensing potential, Te NW arrays were mounted onto the robotic hands equipped with additional wireless transmission functionality for rapid detection of Hg2+ ions in resource-limited settings by employing a simple "touch and sense" mechanism. Such a demonstration of direct integration of self-powered sensors with robotics would lead to the development of low-cost, automated chemical sensing machinery for the on-field detection of harmful analytes.

Programmable Nucleation and Growth of Ultrathin Tellurium Nanowires via a Pulsed Physical Vapor Deposition Design

AbstractPhysical vapor deposition (PVD) methods have been widely employed for high‐quality crystal growth and thin‐film deposition in semiconductor electronics. However, the fabrication of emerging low dimensional nanostructures is hitherto challenging in conventional PVD systems due to their large thermal mass and near‐continuous operation which hinder flexible control of the nucleation and growth events. Herein, a pulsed PVD method is reported that features finely controllable temperature and heating time (down to milliseconds), which enables programming of the vapor supersaturation and decoupling of nucleation and growth events. Take tellurium as an example, the pulsed PVD allows transient source vaporization (≈1000 °C, 30 ms) for burst nucleation, followed by relatively low‐temperature volatilization (≈600 °C, 5 min) for steady‐state growth with well‐suppressed random nucleation. As a result, uniform and high‐density tellurium nanowires are obtained at the ultrathin thickness of sub‐10 nm and length >10 µm, which is in sharp contrast to the randomly formed nanostructures in conventional PVD. When used in the field‐effect transistor, the thin tellurium nanowires display a high on‐off ratio of >104 and hole mobility of ≈40 cm2 V−1 s−1, showing the potential for high‐performance electronics. Pulsed PVD therefore enables to flexibly program and finely tailor the nucleation and growth events during vapor phase deposition, which are otherwise impossible in conventional PVD.

Ultrafast time-resolved carrier dynamics in tellurium nanowires using optical pump terahertz probe spectroscopy.

We report carrier relaxation dynamics in semiconducting tellurium nanowires (average diameter ∼ 10 nm) using ultrafast time-resolved terahertz spectroscopy. After photoexcitation using an 800 nm pump pulse, we observed an initial increase in the THz conductivity due to the absorption of THz radiation by photoexcited carriers. The time evolution of the differential conductivity (Δσ(τpp) = σpump on(τpp) - σpump off) shows a bi-exponential relaxation with the initial fast decay time scale of τ1 ∼ 25 ps followed by a longer relaxation time constant of τ2 ∼ 100 ps. Interestingly, the two time scales depend on the amount of the capping agent present on the surface of TeNWs, showing a faster relaxation of the photoexcited carriers as the percentage of capping decreases. This is physically interpreted as the surface state mediated relaxation mechanism of the photo-pumped carriers depending on the density of available surface states. A quantitative understanding is obtained using a coupled rate equation model taking into account the decay mechanisms determined from the surface mediated relaxation rate (DS) and direct recombination rate (DR) of the electron-hole pairs. Furthermore, the measured lattice temperature (TL) dependent dynamics, showing a faster relaxation at lower temperature, is understood using the same rate equation model, giving a power law dependence of the electron-hole recombination rate (DR) on TL as DR ∝ TL-1/2. This is explained by estimating DR using the van Roosbroeck-Shockley theory taking into account the density of states () of one-dimensional nanowires. Furthermore, to understand the measured frequency-dependent THz photoconductivity, we model Δσ(ω) using the Boltzmann transport equation taking into account the energy-dependent scattering rates showing the dominant role of short range (Γsr) and Coulomb scattering (ΓC) rates in the relaxation process, which further provides a measure of the charged and neutral impurity concentrations.

Optical properties of extreme tellurium nanowires formed in subnanometer-diameter channels.

Single tellurium (Te) chains attract much attention as extreme nanowires with unique electronic and spintronic properties. Here, we encapsulate Te from a melt into channels of zeolites AFI (∼0.73 nm-channel diameter) and mordenite (MOR, ∼0.67 × 0.7 nm2 channel cross-section) via high-pressure injection. Using polarized Raman and optical absorption spectra (RS and OAS) of zeolite single crystals with Te (AFI-Te and MOR-Te), we discriminate between features of Te chains and rings formed in the zeolites. We demonstrate good agreement of AFI-Te-chain RS and OAS with the calculated single Te-helix phonon and electron spectra. This suggests a very weak interaction of the AFI-Te-chain with the zeolite and its nearly perfect helix structure lacking inversion/mirror symmetry. An AFI-Te OAS feature, attributed to the electron transitions between Te-helix-Rashba-split valence and conduction bands confirms its 1D-electron-band origin with predicted possibilities of identifying Majorana fermions, manipulating spin transport and realizing topological superconductivity.

TeNWs/Ti3C2Tx Nanohybrid-Based Flexible Pressure Sensors for Personal Safety Applications Using Morse Code

This report demonstrates the fabrication and development of a tellurium nanowire (TeNW) and MXene (Ti3C2Tx) nanohybrid-based pressure sensor. The fabricated sensor was later encapsulated in poly(dimethylsiloxane) (PDMS) and used as buttons for the communication system to demonstrate a personal safety application using Morse code. The fabricated pressure sensor demonstrated an excellent sensitivity of 9.29241 kPa–1 and stability withstanding over ∼3000 cycles of applied pressure (∼1.729 kPa). Real-time ultraviolet photoelectron spectroscopy (UPS) is utilized for realizing the band diagram of the TeNWs/Ti3C2Tx nanohybrid to understand the transport of charge carriers upon external pressure. The transduction mechanism of the fabricated pressure sensor is explained using the improved intrinsic piezoresistive properties of the MXene and TeNWs in TeNWs/Ti3C2Tx, which helps in increasing the tunneling current by a decrease in the effective interlayer resistance/interwire tunneling distance of the nanohybrid. Further, an Android application was created to wirelessly receive data via Bluetooth from the sensors connected to a microcontroller. The application displayed the pattern pressed on the sensors as a Morse dash or dot. This can further be used in a similar fashion to that of a telegraph to send complex messages such as “HELP”. Developing a TeNWS/Ti3C2Tx nanohybrid-based flexible sensor opens many possible wireless monitoring and communication applications.

Template-free electrochemical deposition of tellurium nanowires with eutectic solvents

Electrochemical deposition of tellurium from deep eutectic solvents (DES) at gold film electrodes produced films of tellurium nanowires. The deposition was evenly distributed over the gold surface, with an average diameter of ∼70 nm and length of ∼1 µm. Deposition was extremely sensitive to the applied potential, tellurium concentration and deposition bath temperature, with deviations away from optimised conditions preventing the formation of the desired nanostructure. Interestingly, replacing the chloride in a popular eutectic solvent with bromide or iodide had a significant impact on the resultant film structure, with bromide giving no clearly defined nanostructure but iodide giving nanoplatelets. This demonstrates a strong control of tellurium nanostructure by halide ions, offering a way to two distinct nanostructures from the same core experimental set up.

Controlled Synthesis of Tellurium Nanowires.

One-dimensional tellurium nanostructures can exhibit distinct electronic properties from those seen in bulk Te. The electronic properties of nanostructured Te are highly dependent on their morphology, and thus controlled synthesis processes are required. Here, highly crystalline tellurium nanowires were produced via physical vapour deposition. We used growth temperature, heating rate, flow of the carrier gas, and growth time to control the degree of supersaturation in the region where Te nanostructures are grown. The latter leads to a control in the nucleation and morphology of Te nanostructures. We observed that Te nanowires grow via the vapour-solid mechanism where a Te particle acts as a seed. Transmission electron microscopy (TEM) and electron diffraction studies revealed that Te nanowires have a trigonal crystal structure and grow along the (0001) direction. Their diameter can be tuned from 26 to 200 nm with lengths from 8.5 to 22 μm, where the highest aspect ratio of 327 was obtained for wires measuring 26 nm in diameter and 8.5 μm in length. We investigated the use of bismuth as an additive to reduce the formation of tellurium oxides, and we discuss the effect of other growth parameters.

Competition of Photo-Excitation and Photo-Desorption Induced Positive and Negative Photoconductivity Switch in Te Nanowires.

The photocurrent in tellurium nanowire (Te NW) exhibits a subtle influence by many extrinsic factors. Herein, we fabricate Te NW devices and explore their photoresponse properties in detail. It is observed that the current increases greatly at low environmental relative humidity (RH) under light illumination, demonstrating an evident positive photoconductivity (PPC). However, the photocurrent reduces at high RH, yielding a typical negative photoconductivity (NPC). In addition, when exposed to a proper relative humidity, Te NW devices show PPC immediately and then transfer to NPC gradually under illumination, exhibiting the RH sensitive PPC/NPC switch. It is proposed that the competition between photo-excitation and photo-desorption is responsible for this subtle switch of PPC/NPC. On the one hand, the adsorbed water molecules on the surface of Te nanowires, acting as electron acceptors, lead to an increase of conductance, exhibiting the PPC phenomenon. On the other hand, the photo-desorption of water molecules from the surface results in a decreased carrier concentration in the Te nanowires, yielding the NPC phenomenon. The in-depth understanding of such charge transfer processes between the absorbed water molecules and Te nanowires provides an effective route to modulate the carrier densities and control the PPC/NPC switch, which will accelerate the design and application of novel optoelectronic nanodevices.

Dual sensing signal decoupling based on tellurium anisotropy for VR interaction and neuro-reflex system application

Anisotropy control of the electronic structure in inorganic semiconductors is an important step in developing devices endowed with multi-function. Here, we demonstrate that the intrinsic anisotropy of tellurium nanowires can be used to modulate the electronic structure and piezoelectric polarization and decouple pressure and temperature difference signals, and realize VR interaction and neuro-reflex applications. The architecture design of the device combined with self-locking effect can eliminate dependence on displacement, enabling a single device to determine the hardness and thermal conductivity of materials through a simple touch. We used a bimodal Te-based sensor to develop a wearable glove for endowing real objects to the virtual world, which greatly improves VR somatosensory feedback. In addition, we successfully achieved stimulus recognition and neural-reflex in a rabbit sciatic nerve model by integrating the sensor signals using a deep learning technique. In view of in-/ex-vivo feasibility, the bimodal Te-based sensor would be considered a novel sensing platform for a wide range application of metaverse, AI robot, and electronic medicine.