Jiuxiang Dai

npj 2D Materials and Applications, Published online: 01 November 2022; doi:10.1038/s41699-022-00353-1

Domain wall enabled steep slope switching in MoS₂ transistors towards hysteresis-free operation

Nature Nanotechnology, Published online: 01 November 2022; doi:10.1038/s41565-022-01231-z

A strong and tough human muscle-like actuator fibre is developed by exploiting 2D graphene fillers within a liquid crystalline elastomer matrix. Reversible percolation of the graphene filler network endows the artificial muscle with a work capacity and power density beyond those of human or mammalian muscles.

Nature Nanotechnology, Published online: 31 October 2022; doi:10.1038/s41565-022-01237-7

The interfacial shear modulus controls the sliding friction of supported two-dimensional materials. Now, experiments demonstrate a reciprocal relationship between friction force per unit contact area and the interfacial shear modulus.

Multi-configurational 2D heterojunctions constructed from Cr_xTe_y self-intercalated crystals are demonstrated by TEM diffraction and atomic STEM imaging. In a Cr₂Te₃-Cr₅Te₈ lateral heterojunction, two phases share the layered CrTe₂ as the backbone, whereas different arrangements of intercalated Cr in vdW gap form distinct magnetic phases. A novel magneto-optical behavior of a sharply stepped hysteresis loop with twice spin flips is revealed for the first time.

Emerging 2D magnetic heterojunctions attract substantial interest due to their potential applications in spintronics. Achieving magnetic phase engineering with structural integrity in 2D heterojunctions is of paramount importance for their magnetism manipulation. Herein, starting with chromium ditelluride (CrTe₂) as the backbone framework, various lateral and vertical magnetic heterojunctions are obtained via self-intercalated 2D chromium telluride (Cr _x Te _y ). A Cr₂Te₃-Cr₅Te₈ lateral heterojunction prototype is demonstrated for the manipulation of magnetic moments under different magnitudes of magnetic excitation, showing a sharply stepped hysteresis loop with a dual spin-flip transition at high Curie temperatures up to 150 and 210 K by magneto-optical Kerr measurement. High-resolution scanning transmission electron microscopy and first-principles calculations reveal a preferred random location of Cr intercalants at the phase boundary, allowing lowering energy associated with crystal field splitting. The overall structural rigidity of chromium-telluride heterostructure with magnetic phase decoupled behaviors is promising for 2D spintronic devices.

npj 2D Materials and Applications, Published online: 31 October 2022; doi:10.1038/s41699-022-00356-y

Single-crystalline nanoribbon network field effect transistors from arbitrary two-dimensional materials

Ultrafast chemical vapor deposition of a high-quality large-area MoS₂ monolayer film is achieved in 60 s using Dragontrail glass as a catalytic substrate. This is among the shortest time to form a continuous centimeter-scale MoS₂ monolayer film. The growth shows good spatial homogeneity, superior crystallinity, and decent electrical properties comparable to those for MoS₂ grown using 10–100 times longer deposition time.

Abstract

Highly efficient growth of a centimeter-scale MoS₂ monolayer film by oxide scale sublimation chemical vapor deposition (OSSCVD) in a time as short as 60 s is reported. Benefiting from the superior catalytic ability of Dragontrail glass (DT-glass) substrate and the controlled large vapor supersaturation of the molybdenum source, the ultrafast deposition of MoS₂ is realized with maintaining large-sized single-crystalline domains over 20 µm at maximum in the film. It is comparable to those reported for MoS₂ grown in tens of minutes and even hours. Similar to the face-to-face precursor feed route, the gas-controlled OSSCVD with a showerhead configuration facilitates a homogeneous and controllable source supply. It enables high-quality monolayer MoS₂ film deposition on 2 × 2 cm² DT-glass with centimeter-scale uniformity confirmed by microscopic, spectroscopic, and electrical characterizations. Back-gate MoS₂ field-effect transistors fabricated on polycrystalline continuous film exhibit the maximum field-effect mobility of 5.1 cm² V⁻¹s⁻¹ and a peak I _on/I _off ratio of 5 × 10⁸. They reach 40 cm² V⁻¹ s⁻¹ and 1.2 × 10⁹, respectively, on single-crystalline domains. These results are even greater than those for MoS₂ grown using 1–2 orders of magnitude longer deposition time and higher temperatures. This study highlights the opportunities for low-cost high-throughput production of large-area high-quality monolayer MoS₂.

Members of the 2D group VA materials (phosphorene, arsenene, antimonene, and bismuthine) have presented their fascinating structures and intriguing electronic properties. The most recent analytical and empirical developments in the fundamental characteristics, fabrication techniques, and potential implementation of 2D group VA materials in this review, along with presenting insights and concerns for the field's future are analyzed.

Abstract

Members of the 2D group VA semiconductors (phosphorene, arsenene, antimonene, and bismuthine) present a new class of 2D materials, which are recently gaining a lot of research interest. These materials possess layered morphology, tunable direct bandgap, high charge carrier mobility, high stability, unique in-plane anisotropy, and negative Poisson's ratio. They prepare the ground for novel and multifunctional applications in electronics, optoelectronics, and batteries. The most recent analytical and empirical developments in the fundamental characteristics, fabrication techniques, and potential implementation of 2D group VA materials in this review, along with presenting insights and concerns for the field's future are analyzed.

Making 2D van der Waals materials by wafer scale synthetic methods in the form of thin films in order to reach the point one day to define dense devices and circuits in a manufacturable manner to enable applications.

Abstract

Wafer scale epitaxial growth of 2D van der Waals materials and heterostructures is of ultimate importance for applications. Using synthetic thin film methods is also important to realize 2D materials which do not exist in nature and cannot be grown in equilibrium in bulk form. In this work, the perspectives in wafer scale growth of 2D van der Waals metallic ferromagnets (FMs) and the combination with other structurally and chemically compatible materials are described to propose functional devices. The areas such as 2D van der Waals ferromagnetic π-junctions for quantum computing, and all 2D magnetic tunnel junctions (MTJs) and spin orbit torque devices which can be used for spintronics are identified. It is foreseen that a new class of Janus materials which can be realized only by epitaxial synthetic methods can enhance the performance of spintronic devices. Finally, this work describes the perspectives to overcome the shortcomings of epitaxial techniques and layer transfer by proposing remote epitaxy for the detachment of 2D materials films from the substrate and the use of liquid substrates or liquid catalysts to achieve single crystalline 2D materials films over large areas on the wafer.

Publication date: October 2022

Source: Materials Today, Volume 59

Author(s): Laurie Winkless

Publication date: October 2022

Source: Materials Today, Volume 59

Author(s): Cordelia Sealy

Publication date: October 2022

Source: Materials Today, Volume 59

Author(s): Cordelia Sealy

Nature Synthesis, Published online: 27 October 2022; doi:10.1038/s44160-022-00185-3

Atomically thin materials have exciting physicochemical properties but multi-element and non-layered 2D materials are difficult to prepare by conventional methods. Now, a flux-assisted method is reported, enabling the synthesis of such 2D materials by confining reaction space.

Nature Nanotechnology, Published online: 27 October 2022; doi:10.1038/s41565-022-01230-0

Isothermal dissolution–diffusion–precipitation of carbon drives continuous epitaxial growth of single-crystal multilayer graphene.

Nature Materials, Published online: 27 October 2022; doi:10.1038/s41563-022-01386-z

Using molecular-beam epitaxy, we synthesize heterostructures of topological insulator Bi2Se3 and the Ising superconductor monolayer NbSe2. By changing the Bi2Se3 thickness, they demonstrate a crossover from Ising- to Rashba-type superconducting pairing.

Nature Electronics, Published online: 27 October 2022; doi:10.1038/s41928-022-00849-0

Gate-tunable heterojunction diodes—or triodes—that are based on van der Waals heterostructures formed from two-dimensional indium selenide and three-dimensional silicon can exhibit subthreshold slopes of 6.4 mV decade–1 and on-state current densities of 0.3 µA µm–1 at a drain bias of –1 V.

In this work, an artificial electronic synaptic device based on gate-all-around InAs nanowire field-effect transistor is proposed and analyzed. The deposited oxide layer (In2O3) on the InAs nanowire surface serve...

Nature Communications, Published online: 27 October 2022; doi:10.1038/s41467-022-33978-3

The ferroelectric material α-GeTe(111) is an excellent playground for spin-to charge conversion due to its strong Rashba coupling. Here, the authors reveal an ultrafast modulation of its Rashba coupling on the femtosecond timescale.

Does adatom adsorption on the surface of a 3D ferromagnet influence electron correlation? A far from trivial question! Using state-of-the-art theoretical and experimental methods, it is found that an iron surface in contact with oxygen represents a moderately correlated system with some features in between metallic Fe and the Mott insulator FeO.

Abstract

Spin-resolved momentum microscopy and theoretical calculations are combined beyond the one-electron approximation to unveil the spin-dependent electronic structure of the interface formed between iron (Fe) and an ordered oxygen (O) atomic layer, and an adsorbate-induced enhancement of electronic correlations is found. It is demonstrated that this enhancement is responsible for a drastic narrowing of the Fe d-bands close to the Fermi energy (E _F) and a reduction of the exchange splitting, which is not accounted for in the Stoner picture of ferromagnetism. In addition, correlation leads to a significant spin-dependent broadening of the electronic bands at higher binding energies and their merging with satellite features, which are manifestations of a pure many-electron behavior. Overall, adatom adsorption can be used to vary the material parameters of transition metal surfaces to access different intermediate electronic correlated regimes, which will otherwise not be accessible. The results show that the concepts developed to understand the physics and chemistry of adsorbate–metal interfaces, relevant for a variety of research areas, from spintronics to catalysis, need to be reconsidered with many-particle effects being of utmost importance. These may affect chemisorption energy, spin transport, magnetic order, and even play a key role in the emergence of ferromagnetism at interfaces between non-magnetic systems.

High-quality single-crystalline ferromagnetic Fe₃N thin films and heterostructures with precisely controlled thickness are fabricated. A strong in-plane magnetic anisotropy and reversal of anomalous Hall resistance are observed when its thickness exceeds 5 unit-cells. Furthermore, the exchange bias effect strongly depends on mechanical bending, yielding to potential innovative applications.

Abstract

Interfacial magnetism stimulates the discovery of giant magnetoresistance (MR) and spin–orbital coupling across the heterointerfaces, facilitating the intimate correlation between spin transport and complex magnetic structures. Over decades, functional heterointerfaces composed of nitrides have seldom been explored due to the difficulty in synthesizing high-quality nitride films with correct compositions. Here, the fabrication of single-crystalline ferromagnetic Fe₃N thin films with precisely controlled thicknesses is reported. As film thickness decreases, the magnetization dramatically deteriorates, and the electronic state changes from metallic to insulating. Strikingly, the high-temperature ferromagnetism is maintained in a Fe₃N layer with a thickness down to 2 u.c. (≈8 Å). The MR exhibits a strong in-plane anisotropy; meanwhile, the anomalous Hall resistivity reverses its sign when the Fe₃N layer thickness exceeds 5 u.c. Furthermore, a sizable exchange bias is observed at the interfaces between a ferromagnetic Fe₃N and an antiferromagnetic CrN. The exchange bias field and saturation moment strongly depend on the controllable bending curvature using the cylinder diameter engineering technique, implying the tunable magnetic states under lattice deformation. This work provides a guideline for exploring functional nitride films and applying their interfacial phenomena for innovative perspectives toward practical applications.

The formation of ultrathin nanowires has thermodynamic advantages at low temperature. However, at low temperatures the monomers for nanocrystal growth are difficult to generate through precursor decomposition. In their Research Article (e202212251), Di Qiu, Yaping Du, and co-workers report an efficient growth process based on adding polyoxometalate clusters to the monomers. Fifteen types of rare earth oxide ultrathin nanowires were synthesized, all exhibiting polymer-like behavior due to the extremely high aspect ratio.

Nature Communications, Published online: 28 October 2022; doi:10.1038/s41467-022-34193-w

Due to their layered structure, and resulting weak interlayer exchange coupling, van der Waals materials can exhibit distinct behaviour depending on whether the spins are aligned in the plane, or perpendicular. Here, via magnetoresistance measurements, Zhu et al provide direct evidence of a magneto-band-structure effect due to the alignment of the spin in the van der Waals magnet, Cr2Ge2Te6.

npj 2D Materials and Applications, Published online: 29 October 2022; doi:10.1038/s41699-022-00350-4

Experimental and theoretical studies of native deep-level defects in transition metal dichalcogenides

Nature Communications, Published online: 29 October 2022; doi:10.1038/s41467-022-34192-x

Twisted double bilayer graphene (tDBG) comprises two Bernal-stacked bilayer graphene sheets with a twist between them. Here, the authors report a strong anomalous Hall effect in the correlated-metal regime of tDBG, indicating time reversal symmetry breaking from orbital ferromagnetism, likely associated with valley polarization.

Publication date: December 2022

Source: Materials Today, Volume 61

Author(s): Yu Han, Tiantian Zuo, Kun He, Lu Yang, Sheng Zhan, Zhike Liu, Zelin Ma, Jie Xu, Yuhang Che, Wenjing Zhao, Ningyi Yuan, Jianning Ding, Jie Sun, Xuexia He, Shengzhong (Frank) Liu

Nature Communications, Published online: 26 October 2022; doi:10.1038/s41467-022-34119-6

The growth of stable and high-mobility semiconductors using industry-compatible methods still attracts interest in electronics community. Here, Noh et al. report wafer-scale ultrathin Bi2S3 and Te semiconductors for high-performance complementary electronics using room temperature thermal evaporation.