Jiuxiang Dai

Nature Nanotechnology, Published online: 10 November 2021; doi:10.1038/s41565-021-01024-w

2D materials grow large

Nature Communications, Published online: 10 November 2021; doi:10.1038/s41467-021-26601-4

Knowing how individual water molecules interact with surfaces is crucial for understanding surface and interface phenomena. Here, the authors show how local water-water interactions enable an unforeseen and surprisingly rapid mechanism of atom exchange between a common mineral and its surroundings.

Light: Science & Applications, Published online: 08 November 2021; doi:10.1038/s41377-021-00659-7

Enhancement in local density of optical states arising from the optical anisotropy of hexagonal boron nitride significantly improves the emission rates of plasmons and photons in quantum mechanical tunnel junctions.

Nature Nanotechnology, Published online: 08 November 2021; doi:10.1038/s41565-021-01003-1

A retina-inspired two-dimensional material based retinomorphic device exhibits all-in-one perception, memory and computing capabilities for motion detection and recognition.

Nature Nanotechnology, Published online: 10 November 2021; doi:10.1038/s41565-021-01024-w

2D materials grow large

Nature Electronics, Published online: 22 October 2021; doi:10.1038/s41928-021-00657-y

A monolayer of tungsten oxyselenide, created by oxidizing a layer of tungsten diselenide, can be used to efficiently dope graphene, leading to a room-temperature mobility of 2,000 cm2 V–1 s–1 at a hole density of 3 × 1013 cm–2.

Nature Electronics, Published online: 22 October 2021; doi:10.1038/s41928-021-00668-9

Ion implantation can be used to dope silicon devices, but can be problematic when applied to the atomically thin crystal structure of two-dimensional materials — an increasing range of alternative methods is though available.

Nature Electronics, Published online: 22 October 2021; doi:10.1038/s41928-021-00666-x

Germanium pyramids see the light

Publication date: December 2021

Source: Materials Today, Volume 51

Author(s): Guozhen Liang, Xuechao Yu, Xiaonan Hu, Bo Qiang, Chongwu Wang, Qi Jie Wang

Nature Communications, Published online: 10 November 2021; doi:10.1038/s41467-021-26601-4

Knowing how individual water molecules interact with surfaces is crucial for understanding surface and interface phenomena. Here, the authors show how local water-water interactions enable an unforeseen and surprisingly rapid mechanism of atom exchange between a common mineral and its surroundings.

Two-dimensional (2D) palladium ditelluride (PdTe 2 ) and platinum ditelluride (PtTe 2 ) are two Dirac semimetals, which have fascinating quantum properties such as superconductivity, magnetism and topological order and show the promising applications in future nanoelectronics and optoelectronics. However, the synthesis of PdTe 2 and PtTe 2 monolayers (MLs) is hindered by a strong interlayer coupling and orbital hybridization. In this study, we demonstrate an efficient synthesis of PdTe 2 and PtTe 2 MLs Large-area and high quality MLs of PdTe 2 and patterned PtTe 2 were epitaxially grown on the Pd(111) and Pt(111) surfaces by direct telurization in ultra-high vacuum. This was confirmed by x-ray photoelectron spectroscopy, low energy electron diffraction and scanning tunnelling microscopy. PdTe 2 ML demonstrated high thermal stability showing no decomposition sign after annealing at 470 °C. A w...

Light: Science & Applications, Published online: 08 November 2021; doi:10.1038/s41377-021-00659-7

Enhancement in local density of optical states arising from the optical anisotropy of hexagonal boron nitride significantly improves the emission rates of plasmons and photons in quantum mechanical tunnel junctions.

The potential of fusing 2D materials with silicon technologies, including 2D logic and memory devices, enabling the mitigation of challenges related to silicon integrated circuits (ICs) and even the creation of technologies beyond silicon, is highlighted. The progress of 2D IC applications and the prospects for realizing wafer-scale heterogeneous integration compatible with silicon ICs are also summarized.

Abstract

Continued reduction in transistor size can improve the performance of silicon integrated circuits (ICs). However, as Moore's law approaches physical limits, high-performance growth in silicon ICs becomes unsustainable, due to challenges of scaling, energy efficiency, and memory limitations. The ultrathin layers, diverse band structures, unique electronic properties, and silicon-compatible processes of 2D materials create the potential to consistently drive advanced performance in ICs. Here, the potential of fusing 2D materials with silicon ICs to minimize the challenges in silicon ICs, and to create technologies beyond the von Neumann architecture, is presented, and the killer applications for 2D materials in logic and memory devices to ease scaling, energy efficiency bottlenecks, and memory dilemmas encountered in silicon ICs are discussed. The fusion of 2D materials allows the creation of all-in-one perception, memory, and computation technologies beyond the von Neumann architecture to enhance system efficiency and remove computing power bottlenecks. Progress on the 2D ICs demonstration is summarized, as well as the technical hurdles it faces in terms of wafer-scale heterostructure growth, transfer, and compatible integration with silicon ICs. Finally, the promising pathways and obstacles to the technological advances in ICs due to the integration of 2D materials with silicon are presented.

Floating catalyst chemical vapor deposition (FCCVD) method is widely used to produce high quality carbon nanotubes (CNTs) due to its simple processing, good controllability, and desirable scalability. This review summarizes the state-of-the-art progress in the controlled growth and applications of the CNTs and their macrostructures by FCCVD. The critical challenges and future perspectives are also discussed.

Abstract

Floating catalyst chemical vapor deposition (FCCVD) has been one of the most important techniques for the synthesis of high-quality single-, double-, and multi-wall carbon nanotubes (CNTs). The method is characterized of simple processing, good controllability, and desirable scalability. The bulk morphologies of the synthesized CNTs can be sponge-like, an array, a thin film, or fiber by simply changing the growth parameters and the way they are collected, which facilitates a wide range of applications. The authors comprehensively review the state-of-the-art progress on the controlled growth of CNTs by FCCVD which have a defined number of walls, and controlled diameter, bundle size, and type of conductivity. The properties and possible applications for the CNTs and their hybrids are summarized. Finally, insights into the key challenges and prospects for CNTs synthesized by FCCVD are discussed.

Van der Waals antiferromagnet CrPS₄ undergoes a spin-reorientation transition with magnetic moments realigning from almost parallel to the c axis in the ac plane to along the b axis upon heating. The transition is dramatically suppressed by hydrostatic pressure, offering an effective way to control the Néel vector of antiferromagnets.

Abstract

Controlling the phases of matter is a central task in condensed matter physics and materials science. In 2D magnets, manipulating spin orientation is of great significance in the context of the Mermin–Wagner theorem. Herein, a systematic study of temperature- and pressure-dependent magnetic properties up to 1 GPa in van der Waals CrPS₄ is reported. Owing to the temperature-dependent change of the magnetic anisotropy energy, the material undergoes a first-order spin reorientation transition with magnetic moments realigning from being almost parallel with the c axis in the ac plane to the quasi-1D chains of CrS₆ octahedra along the b axis upon heating. The spin reorientation temperature is suppressed after applying pressure, shifting the high-temperature phase to lower temperatures with the emergence of spin-flop transitions under magnetic fields applied along the b axis. The saturation field increases with pressure, indicating the enhancement of interlayer antiferromagnetic coupling. However, the Néel temperature is slightly reduced, which is ascribed to the suppression of intralayer ferromagnetic coupling. The work demonstrates the control of spin orientation and metamagnetic transitions in layered antiferromagnets, which may provide new perspectives for exploring 2D magnetism and related spintronic devices.

This work presents the synthesis of 2D ultrathin metastable γ-Bi₂O₃ flakes via a van der Waals epitaxy method. The UV photodetectors based on the as-synthesized γ-Bi₂O₃ flakes exhibit excellent performance, where the responsivity is 64.5 A W⁻¹, specific detectivity is 1.3 × 10¹³ Jones, and response time is 290 µs under 365 nm laser illumination.

Abstract

Ultraviolet detection is of great significance due to its wide applications in the missile tracking, flame detecting, pollution monitoring, and so on. The nonlayered semiconductor γ-Bi₂O₃ is a promising candidate toward high-performance UV detection due to the wide bandgap, excellent light sensitivity, environmental stability, nontoxic and elemental abundance properties. However, controllable preparation of ultrathin 2D γ-Bi₂O₃ flakes remains a challenge, owing to its nonlayered structure, metastable nature, and other competing phases. Moreover, the UV photodetectors based on 2D γ-Bi₂O₃ flake have not been implemented yet. Here, ultrathin (down to 4.8 nm) 2D γ-Bi₂O₃ flakes with high crystal quality are obtained via a van der Waals epitaxy method. The as-synthesized single-crystalline γ-Bi₂O₃ flakes show a body-centered cubic structure and grown along (111) lattice plane as revealed by experimental observations. More importantly, photodetectors based on the as-synthesized 2D γ-Bi₂O₃ flakes exhibit promising UV detection ability, including a responsivity of 64.5 A W⁻¹, a detectivity of 1.3 × 10¹³ Jones, and an ultrafast response speed (τ_rise ≈ 290 µs and τ_decay ≈ 870 µs) at 365 nm, suggesting its great potential for various optoelectronic applications.

A prototype of active sites separation over 1T-MoS₂ is proposed in which the Mo-edge and S atoms exhibit different catalytic NRR and HER selectivity. Benefiting from the active site separation, the 1T phase can accelerate both NRR and HER, but prefer the former, thus achieving the synchronization of selectivity and activity toward the NRR.

Abstract

The 1T phase of MoS₂ has been widely reported to be highly active toward the hydrogen evolution reaction (HER), which is expected to restrict the competitive nitrogen reduction reaction (NRR). However, in this work, a prototype of active sites separation over 1T-MoS₂ is proposed by DFT calculations that the Mo-edge and S atoms on the basal plane exhibit different catalytic NRR and HER selectivity, and a new role-playing synergistic mechanism is also well enabled for the multistep NRR, which is further experimentally confirmed. More importantly, a self-sacrificial strategy using g-C₃N₄ as templates is proposed to synthesize 1T-MoS₂ with an ultrahigh 1T content (75.44%, named as CNMS, representing the composition elements of C, N, Mo, and S), which yields excellent NRR performances with an ammonia formation rate of 71.07 µg h^–1 mg^–1 _cat. at −0.5 V versus RHE and a Faradic efficiency of 21.01%. This work provides a promising new orientation of synchronizing the selectivity and activity for the multistep catalytic reactions.

Publication date: November 2021

Source: Materials Today, Volume 50

Author(s): Cordelia Sealy

Publication date: November 2021

Source: Materials Today, Volume 50

Author(s): Laurie Donaldson