Two-dimensional Tellurene Research Articles

Weyl Node-Participated Magnetoresistance and Nonreciprocal Transport in Two-Dimensional Tellurene Nanostructures

Weyl Node-Participated Magnetoresistance and Nonreciprocal Transport in Two-Dimensional Tellurene Nanostructures

An extremely low-power-consumption reconfigurable two-dimensional tellurene artificial synapse for bio-inspired wearable edge computing

We fabricated a reconfigurable two-dimensional tellurene artificial synaptic transistor on a flexible substrate for bio-inspired wearable neuromorphic edge computing, showing an extremely low power consumption of 9 fJ and an impressive accuracy of 93% in recognizing MNIST patterns.

Strain controllable band alignment and the interfacial and optical properties of tellurene/GaAs van der Waals heterostructures.

By using first principles calculations, we theoretically investigate the electronic structures and the interfacial and optical properties of the two-dimensional tellurene (Te)-gallium arsenide (GaAs) van der Waals heterostructures (vdWHs), i.e., α-Te/GaAs and γ-Te/GaAs, formed using Te and GaAs monolayers. It has been demonstrated that, the semiconductor-semiconductor contacted α-Te/GaAs vdWH exhibits a type-II band alignment with a direct band gap of 0.28 eV while the metal-semiconductor contacted γ-Te/GaAs vdWH has a p-type Schottky contact with a Schottky barrier height (SBH) of 0.36 eV at the interface. The transition from type-II to type-III band alignment is observed firstly in the α-Te/GaAs vdWH when the in-plane biaxial strain is less than -5.2% and larger than 4.4%, meanwhile, the p-type Schottky contact to Ohmic contact transition may be realized in the γ-Te/GaAs vdWH when the in-plane biaxial strain is less than -2.4%. Finally, the maximum optical absorption coefficients of the α- and γ-Te/GaAs vdWHs have been found to be up to 31% and 29%, respectively, and may be modulated effectively by applying in-plane biaxial strain. The obtained results may be of importance in the design of nanoelectronic devices based on the proposed tellurene/GaAs vdWHs.

Environmentally Stable and Reconfigurable Ultralow-Power Two-Dimensional Tellurene Synaptic Transistor for Neuromorphic Edge Computing.

While neuromorphic computing can define a new era for next-generation computing architecture, the introduction of an efficient synaptic transistor for neuromorphic edge computing still remains a challenge. Here, we envision an atomically thin 2D Te synaptic device capable of achieving a desirable neuromorphic edge computing design. The hydrothermally grown 2D Te nanosheet synaptic transistor apparently mimicked the biological synaptic nature, exhibiting 100 effective multilevel states, a low power consumption of ∼110 fJ, excellent linearity, and short-/long-term plasticity. Furthermore, the 2D Te synaptic device achieved reconfigurable MNIST recognition accuracy characteristics of 88.2%, even after harmful detergent environment infection. We believe that this work serves as a guide for developing futuristic neuromorphic edge computing.

Morphology-controlled green synthesis of tellurium nanostructures and applications of Te/MXene hybrid structures

Morphology-controlled Te nanostructures are synthesized by a viable and eco-friendly solution process, realizing the formation of high-quality two-dimensional tellurene and one-dimensional Te nanotubes, nanowires, and nanocables.

Superlubricity in bilayer isomeric tellurene and graphene/tellurene van der Waals heterostructures

The molecular dynamics (MD) method was used to study the superlubricity in two-dimensional tellurene isomers (α-Te/β-Te), and in two-dimensional tellurene and graphene (G/α-Te, G/β-Te) heterostructures. We find that their friction characteristics are completely different. The α-Te/β-Te system increases the incommensurate contact between layers by torsion, however, the superlubricity phenomenon cannot occur. The friction coefficient of stacking G/β-Te changes slightly under different stacking structures, but varies obviously with sliding direction, sliding speed and normal load. For the G/α-Te system, the results show that one can obtain superlubricity in a wide range of interlayer angle. Moreover, the superlubricity in G/α-Te is almost invariant with the slip direction, the slip speed and the normal load, indicating that it is a new superlubricity system with potential applications. The present study extends the superlubricity system and helps to understand the tribology properties in the two-dimensional materials.

Surface Adsorption and Vacancy in Tuning the Properties of Tellurene.

The emerging two-dimensional tellurene has been demonstrated to be a promising candidate for photoelectronic devices. However, there is a lack of comprehensive insight into the effects of vacancies and common adsorbates (i.e., O2 and H2O) in ambient conditions, which play a crucial role in semiconducting devices. In this work, with the aid of first-principles calculations, we demonstrate that H2O and O2 molecules behave qualitatively differently on tellurene, while water adsorption can be remarkably promoted by adjacent preadsorbed O2. Upon the formation of Te vacancies, the adsorption of both O2 and H2O molecules is enhanced. More importantly, the existence of H2O and Te vacancies can dramatically facilitate the dissociation of O2, suggesting that tellurene may be readily oxidized in humid conditions. In addition, it is found that the electronic properties of tellurene are well preserved upon either H2O or O2 adsorption on the surface. In sharp contrast, vacancies enable significant modification on the band structure. Specifically, an indirect-to-direct band gap transition is found at a vacancy concentration of 5.3%.

Two-dimensional tellurene nanosheets as saturable absorber of passively Q-switched Nd:YAG solid-state laser

For the first time, a group-VI single element nanomaterial was used as the optical saturable absorber (SA) to generate laser pulses. With two-dimensional (2D) tellurene as a passive Q-switch, 1.06 μm and 1.3 μm pulse laser operations were realized from a diode-pumped Nd:YAG crystal. The shortest pulse widths were 98 ns and 178 ns, and the highest peak powers were 2.68 W and 2.45 W, respectively. Our research determines that tellurene is an excellent SA material in the near-infrared region.

Electronic and Optical Properties of Two-Dimensional Tellurene: From First-Principles Calculations.

Tellurene is a new-emerging two-dimensional anisotropic semiconductor, with fascinating electric and optical properties that differ dramatically from the bulk counterpart. In this work, the layer dependent electronic and optical properties of few-layer Tellurene has been calculated with the density functional theory (DFT). It shows that the band gap of the Tellurene changes from direct to indirect when layer number changes from monolayer (1 L) to few-layers (2 L–6 L) due to structural reconstruction. Tellurene also has an energy gap that can be tuned from 1.0 eV (1 L) to 0.3 eV (6 L). Furthermore, due to the interplay of spin–orbit coupling (SOC) and disappearance of inversion symmetry in odd-numbered layer structures resulting in the anisotropic SOC splitting, the decrease of the band gap with an increasing layer number is not monotonic but rather shows an odd-even quantum confinement effect. The optical results in Tellurene are layer dependent and different in E ⊥ C and E || C directions. The correlations between the structure, the electronic and optical properties of the Tellurene have been identified. Despite the weak nature of interlayer forces in their structure, their electronic and optical properties are highly dependent on the number of layers and highly anisotropic. These results are essential in the realization of its full potential and recommended for experimental exploration.

Phase transition in two-dimensional tellurene under mechanical strain modulation

We carry out computational simulations based on density functional theory (DFT) to investigate different phases of two-dimensional (2-D) tellurene. These phases are classified by their characteristic space groups and symmetry elements. Correlations of these phases to the bulk crystalline tellurium structure are also illustrated. Our specific interests include mechanical property calculations for different phases and the possible phase transitions between them. Simulation results show that these 2-D Te phases have very different elastic moduli due to their different atomic bonding and relaxed structures. Moreover, compression along the in-plane directions facilitates the α → β phase transition, while in-plane tensile strains always make the α-phase more stable than the β-phase. However, the energy difference between the two phases is comparable to or even much smaller than the thermal energy kT, depending on the in-plane strain direction. We find that further increase of the tensile strain along the chain direction beyond a critical value, ca. 12%, may lead to a possible α → γ phase transition. As the tensile strain is above 15%, the γ-phase will be more stable than the α-phase, accompanied by a further reduced transition energy barrier.

Highly-efficient heterojunction solar cells based on two-dimensional tellurene and transition metal dichalcogenides

Tellurene and TMDs show desirable type II band alignment for constructing highly-efficient heterojunction solar cells with strong charge separation and enhanced sunlight absorption.

Two-Dimensional Tellurene as Excellent Thermoelectric Material

We study the thermoelectric properties of two-dimensional tellurene by first-principles calculations and semiclassical Boltzmann transport theory. The HSE06 hybrid functional results in a moderate direct band gap of 1.48 eV at the Γ point. A high room temperature Seebeck coefficient (Sxx = 0.38 mV/K, Syy = 0.36 mV/K) is combined with anisotropic lattice thermal conductivity (κxxl = 0.43 W/m K, κyyl = 1.29 W/m K). Phonon band structures demonstrate a key role of optical phonons in the record low thermal conductivity that leads to excellent thermoelectric performance of tellurene. At room temperature and moderate hole doping of 1.2 × 10–11 cm–2, for example, a figure of merit of ZTxx = 0.8 is achieved.

Field-effect transistors made from solution-grown two-dimensional tellurene

The reliable production of two-dimensional crystals is essential for the development of new technologies based on 2D materials. However, current synthesis methods suffer from a variety of drawbacks, including limitations in crystal size and stability. Here, we report the fabrication of large-area, high-quality 2D tellurium (tellurene) using a substrate-free solution process. Our approach can create crystals with a process-tunable thickness, from monolayer to tens of nanometres, and with lateral sizes of up to 100 um. The chiral-chain van der Waals structure of tellurene gives rise to strong in-plane anisotropic properties and large thickness dependent shifts in Raman vibrational modes, which is not observed in other 2D layered materials. We also fabricate tellurene field-effect transistors, which exhibit air-stable performance at room temperature for over two months, on off ratios on the order of 106 and field-effect mobilities of around 700 cm2 per Vs. Furthermore, by scaling down the channel length and integrating with high-k dielectrics, transistors with a significant on-state current density of 1 A mm-1 are demonstrated.