zemin zheng

The design and synthesis of efficient catalysts for water oxidation is of significant importance. Here a type of graphdiyne (GDY) based heterostructure of CdSe/GDY was synthesized through a facile in-situ growth strategy including the first growth of GDY nanosheet arrays followed by the nucleation and growth of CdSe quantum dots (QDs) featuring well-dispersed CdSe QDs with uniform size around 3 nm. Experimental results revealed that GDY could effectively induce the growth and well-dispersion of CdSe QDs on GDY, forming new heterostructures and leading to the maximized number of active sites, the reduced recombination of photo-induced electron and hole pairs, and facilitated charge transfer behavior. Benefiting from these superior advantages, CdSe/GDY achieves greatly enhanced catalytic activity toward water oxidation under light illumination, with a small overpotential of 155 mV at the current density of 10 mA cm −2 , which is better than those of pristine CdSe Q...

Nature Communications, Published online: 11 October 2021; doi:10.1038/s41467-021-26201-2

An enhanced superconducting pairing temperature (Tg) has only been observed in single-layer FeSe interfaced with TiOx system. Here, the authors construct a new interface composed of single-layer FeSe interfaced with LaFeO3 showing a highest Tg of 80 K among all-known interfacial superconductors.

We have obtained single phase monolayer germanene on aluminum (111) thin films grown on a germanium (111) template by atomic segregation epitaxy, a preparation method differing from molecular beam epitaxy used in previous works. This 2 × 2 reconstructed germanene phase matching an Al(111)3 × 3 supercell has been prepared in large areas upon annealing at 430 °C. Detailed studies have been carried out using scanning tunneling microscopy (STM), low-energy electron diffraction, Auger electron spectroscopy, and synchrotron radiation photoemission spectroscopy. First-principles calculations based on the density function theory along with atomic-scale STM images reveal the atomic structure with one protruding Ge atom per 2 × 2 germanene supercell and a characteristic dispersing band originating from the germanene sheet slightly coupled to the first layer Al atoms underneath. Instead, upon annealing at lower temperatures, multi-phase regions comprise twisted germanene domains in corresp...

Two-dimensional (2D) materials with puckered layer morphology are promising candidates for next-generation optoelectronics devices owing to their anisotropic response to external perturbations and wide band gap tunability with the number of layers. Among them, palladium diselenide (PdSe 2 ) is an emerging 2D transition-metal dichalcogenide, with a band gap ranging from ##IMG## [http://ej.iop.org/images/2053-1583/8/4/045036/tdmac255aieqn1.gif] {$\sim1.3$} eV in the monolayer to a predicted semimetallic behaviour in the bulk. Here, we use angle-resolved photoemission spectroscopy to explore the electronic band structure of PdSe 2 with energy and momentum resolution. Our measurements reveal the semiconducting nature of the bulk. Furthermore, constant binding-energy maps of reciprocal space display a remarkable site-specific sensitivity to the atomic arrangement and its symmetry. Supported by density functional theory calculations, we ascribe...

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...

Nature Communications, Published online: 24 September 2021; doi:10.1038/s41467-021-25922-8

Twisted van der Waals systems are known to host flat electronic bands, originating from moire potential. Here, the authors predict from purely geometric considerations a new type of nearly dispersionless bands in twisted bilayer MoS2, resulting from destructive interference between effective lattice hopping matrix elements.

Nature Communications, Published online: 24 September 2021; doi:10.1038/s41467-021-25941-5

Naturally occurring hyperbolic polaritons exist in a class of layered materials. Here, the authors show evidence, via optical spectroscopy, of hyperbolic exciton-polaritons in phosphorene, originating from its in-plane anisotropy and strong exciton resonances.

Photoluminescence (PL) of transition metal dichalcogenide (TMD) monolayers is strongly influenced by the dielectric environment. The defect states present in the substrate induces uncontrollable doping in the TMD monolayer and thereby modifies the PL spectra. There have been enormous efforts to tune and overcome the effect of inevitable substrate defects in PL spectra, but a proper understanding and a convenient way are still lacking. Here, we systematically studied the effect of surface defects by gradually increasing the separation between WS 2 monolayer and substrate. Hence, we could precisely modulate the exciton and trion contribution in the PL spectra of WS 2 . The excitation power dependant measurements on dielectric engineered and patterned substrates helped us to shed light on the mechanism of PL modulation in monolayer WS 2 . We have also studied the influence of the nature of the charge carried by substrate defects on the PL spectra. These ...

Two-dimensional layered materials have attracted a lot of attention as building block in memristive devices owing to their high downscaling potential, easy stacking due to van der Waals forces and mechanical flexibility. In this study, memristive switching is explored in vertical device structures based on layered Sb 2 Te 3 . For this, epitaxial 2D-like Sb 2 Te 3 thin films with thicknesses of ∼20 nm were directly grown on conductive p-type Si (111) substrates by pulsed laser deposition. Analog programmability mimicking neuromorphic operation, stable multilevel retention and endurance performance with a memory window larger than one order of magnitude are achieved by utilizing Ag as electrode metal. However, Cu top electrodes lead to a memristive switching with generally smaller memory window and volatility of programmed states. Devices with both electrode metals offer forming-free operation and self-compliance. Structural and chemical charac...

Two-dimensional van der Waals (vdWs) materials have gathered a lot of attention recently. However, the majority of these materials have Curie temperatures that are well below room temperature, making it challenging to incorporate them into device applications. In this work, we synthesized a room-temperature vdW magnetic crystal Fe 5 GeTe 2 with a Curie temperature T ##IMG## [http://ej.iop.org/images/2053-1583/8/4/045030/tdmac2028ieqn1.gif] {$_c = 332$} K, and studied its magnetic properties by vibrating sample magnetometry (VSM) and broadband ferromagnetic resonance (FMR) spectroscopy. The experiments were performed with external magnetic fields applied along the c -axis ( H ##IMG## [http://ej.iop.org/images/2053-1583/8/4/045030/tdmac2028ieqn2.gif] {$\parallel$} c ) and the ab -plane ( H ##IMG## [http://ej.iop.org/images/2053-1583/8/4/045030/tdmac...] {$\parallel$}

Nature Communications, Published online: 24 August 2021; doi:10.1038/s41467-021-25306-y

A facile and cost-effective synthesis of MXenes is not yet available. Here, the authors propose a one-pot molten salt-based method of MXenes synthesis from elemental precursors in an air atmosphere. Li-ion storage properties of the MXenes are also reported and discussed.