Shixuan Du

Chinese Academy of Sciences | CAS · Institute of Physics

Amorphous materials exhibit various characteristics that are not featured by crystals and can sometimes be tuned by their degree of disorder (DOD). Here, we report results on the mechanical properties of monolayer amorphous carbon (MAC) and monolayer amorphous boron nitride (maBN) with different DOD. The pertinent structures are obtained by kinetic...

Discovery of materials using “bottom-up” or “top-down” approach is of great interest in materials science. Layered materials consisting of two-dimensional (2D) building blocks provide a good platform to explore new materials in this respect. In van der Waals (vdW) layered materials, these building blocks are charge neutral and can be isolated from...

Adatom engineering represents a highly promising opportunity for enhancing electrochemical CO reduction reaction (CORR). However, the aggregation of adatoms under typical reaction conditions often leads to a decline in catalyst activity. Recent studies have revealed that N-heterocyclic carbene (NHC) can stabilize surface adatoms. Herein, based on d...

Magnetic materials could realize the intriguing quantum anomalous Hall effect and metal-to-insulator transition when combined with band topology or electronic correlation, which have broad prospects in quantum information, spintronics, and valleytronics. Here, we propose the approach of designing novel two-dimensional (2D) magnetic states via d-orb...

Copper selenide (Cu2Se) has attracted significant attention due to the extensive applications in thermoelectric and optoelectronic devices over the last few decades. Among various phase structures of Cu2Se, layered Cu2Se exhibits unique properties, such as purely thermal phase transition, high carrier mobility, high optical absorbance and high phot...

Phonons have provided an ideal platform for a variety of intriguing physical states, such as non-Abelian braiding and the Haldane model. It is promising that phonons will realize the complicated nodal states accompanying unusual quantum phenomena. Here, we propose the hybrid nodal surface and nodal line (NS+NL) phonons beyond the single-genre nodal...

Adatom engineering represents a highly promising opportunity for enhancing electrochemical CO 2 reduction reaction (CO 2 RR). However, the aggregation of adatoms under typical reaction conditions often leads to a decline in catalyst activity. Recent studies have revealed the N-heterocyclic carbene (NHC) can stabilize surface adatoms. Herein, based...

Origami offers two-dimensional (2D) materials with great potential for applications in flexible electronics, sensors, and smart devices. However, the dynamic process, which is crucial to construct origami, is too fast to be characterized by using state-of-the-art experimental techniques. Here, to understand the dynamics and kinetics at the atomic l...

The recent successful fabrication of two-dimensional (2D) CoO with nanometer-thickness provides motivation to investigate monolayer CoO due to possible magnetic properties induced by Co atoms. Here, we employ first-principles calculations to show that monolayer CoO is a 2D spin-spiral semiconductor with a honeycomb lattice. The calculated phonon di...

Furazan macrocyclic compound 3,4:7,8:11,12:15,16-tetrafurazan-1,9-dioxazo-5,13- diazocyclohexadecane (DOATF) is an ideal energetic material with high heat of formation. Here, using scanning tunneling microscopy (STM) and non-contact atomic force microscopy (nc-AFM), we investigated the adsorption structure of DOATF molecules on Au(111) surface, whi...

Nonlinear optical (NLO) materials are of great importance for applications in lasers, atomic clocks, free‐space communication, etc. Herein, inspired by the recent prediction of excellent second harmonic generation (SHG) performance in van der Waals (vdW) materials with 1D building blocks, 14 new NLO materials are found from 244 bulk crystals constr...

In twisted h−BN/graphene heterostructures, the complex electronic properties of the fast-traveling electron gas in graphene are usually considered to be fully revealed. However, the randomly twisted heterostructures may also have unexpected transition behaviors, which may influence the device performance. Here, we study the twist-angle-dependent co...

The auxetic effect in two-dimensional (2D) materials can not only enhance their mechanical properties but also brings additional tunability of their physical properties. Here, we employ density-functional-theory calculations to report on a class of auxetic 2D magnets, namely, the squarely packed transition metal dichlorides MCl2 (M = Ti, V, Mn, Fe,...

Databases for charge-neutral two-dimensional (2D) building blocks (BBs), i.e., 2D materials, have been built for years due to their applications in nanoelectronics. Though lots of solids are constructed from charged 2DBBs, a database for them is still missing. Here, we identify 1028 charged 2DBBs from Materials Project database using a topological-...

Nonvolatile electrical control of spin polarization in two-dimensional (2D) magnetic semiconductors is greatly appealing toward future low-dissipation spintronic nanodevices. Here, we report a 2D material VSeF, which is an intrinsic bipolar magnetic semiconductor (BMS) featured with opposite spin-polarized valence and conduction band edges. We then...

Zigzag graphene nanoribbons (ZGNRs) with spin-polarized edge states have potential applications in carbon-based spintronics. The electronic structure of ZGNRs can be effectively tuned by different widths or dopants, which requires delicately designed monomers. Here, we report the successful synthesis of ZGNR with a width of eight carbon zigzag line...

Cobalt-based catalysts have been widely used for Fischer-Tropsch synthesis (FTS) in industry; however, achieving rational catalyst design at the atomic level and thereby a higher activity and more long-chain-hydrocarbon products simultaneously remain an attractive and difficult challenge. The dual-atomic-site catalysts with unique electronic and ge...

Correlation of lattice vibrational properties with local atomic configurations in materials is essential for elucidating functionalities that involve phonon transport in solids. Recent developments in vibrational spectroscopy in a scanning transmission electron microscope have enabled direct measurements of local phonon modes at defects and interfa...

The self-assembly of nanoparticles (NPs) into ordered superlattices is a powerful strategy to fabricate functional nanomaterials. Subtle variations in the interactions between NPs will influence the self-assembled superlattices. Using all-atom molecular dynamics simulations, we explore the self-assembly of 16 gold NPs, 4 nm in diameter, capped with...

Stacking two-dimensional layered materials such as graphene and transitional metal dichalcogenides with nonzero interlayer twist angles has recently become attractive because of the emergence of novel physical properties. Stacking of one-dimensional nanomaterials offers the lateral stacking offset as an additional parameter for modulating the resul...

Two-dimensional honeycomb lattices show great potential in the realization of Dirac nodal line fermions (DNLFs). Here, we successfully synthesized a gold telluride (AuTe) monolayer by direct tellurizing an Au(111) substrate. Low energy electron diffraction measurements reveal that it is (2×2) AuTe layer stacked onto (3×3) Au(111) substrate. Moreove...

Two-dimensional (2D) ferroelectric (FE) materials with relatively low switching barrier and large polarization are promising candidates for next-generation miniaturized nonvolatile memory devices. Herein, we screen out 39 new 2D ferroelectric materials, MX (M: Group III-V elements; X: Group V-VII elements), in three phosphorus-analogue phases inclu...

The quest for electric-field control of nanoscale magnetic states such as skyrmions, which would impact the field of spintronics, has led to a challenging search for multiferroic materials or structures with strong magnetoelectric coupling and efficient electric-field control. Here we report a theoretical prediction that such phenomena can be reali...

Covalently bonded ceramics exhibit preeminent properties-including hardness, strength, chemical inertness, and resistance against heat and corrosion-yet their wider application is challenging because of their room-temperature brittleness. In contrast to the atoms in metals that can slide along slip planes to accommodate strains, the atoms in covale...

Selective C–H bond activation is one of the most challenging topics for organic reactions. The difficulties arise not only from the high C–H bond dissociation enthalpies but also the existence of multiple equivalent/quasi-equivalent reaction sites in organic molecules. Here, we successfully achieve the selective activation of four quasi-equivalent...

Developing efficient catalysts is of paramount importance to oxygen evolution, a sluggish anodic reaction that provides essential electrons and protons for various electrochemical processes, such as hydrogen generation. Here, we report that the oxygen evolution reaction (OER) can be efficiently catalyzed by cobalt tetrahedra, which are stabilized o...

Metal halide perovskites have exceptional potential for future generations of light‐emitting diodes and solar cells. Compared to widely used solution‐based syntheses, vapor‐phase deposition (VPD) offers a fabrication route that can be more easily scaled up for commercial production. Cesium lead halides (CsPbX3) have shown great color purity, high p...

Two-dimensional (2D) superconducting states have attracted much recent interest, especially when they coexist with nontrivial band topology which affords a promising approach towards Majorana fermions. Using first-principles calculations, we predict van der Waals monolayered transition-metal monohalides MX ( M = Zr, Mo; X = F, Cl) as a class of 2D...

Stacking two-dimensional layered materials such as graphene and transitional metal dichalcogenides with nonzero interlayer twist angles has recently become attractive because of the emergence of novel physical properties. Stacking of one-dimensional nanomaterials offers the lateral stacking offset as an additional parameter for modulating the resul...

Amorphous materials feature localization of electrons and phonons that alter the electronic, mechanical, thermal, and magnetic properties. Here, we report calculations of the in-plane thermal conductivities of monolayer amorphous carbon and monolayer amorphous boron nitride, by reverse nonequilibrium molecular dynamics simulations. We find that the...

Functionalized two-dimensional (2D) materials play an important role in both fundamental sciences and practical applications. The construction and precise control of patterns at the atomic-scale are necessary for selective and multiple functionalization. Here we report the fabrication of monolayer pentasilver diselenide (Ag5Se2), a new type of intr...

The quest for electric-field control of nanoscale magnetic states such as skyrmions, which would impact the field of spintronics, has led to a challenging search for multiferroic materials or structures with strong magnetoelectric coupling and efficient electric-field control. Here we report a theoretical prediction that such phenomena can be reali...

We report a facile phase conversion method that can locally convert n-type SnSe 2 into p-type SnSe by direct laser irradiation. Raman spectra of SnSe 2 flakes before and after laser irradiation confirm the phase conversion of SnSe 2 to SnSe. By performing the laser irradiation on SnSe 2 flakes at different temperatures, it is found that laser heati...

Self‐assembly of cyclohexyl cyclic (alkyl)(amino)carbenes (cyCAAC) can be realized and reversibly switched from a close‐packed trimer phase to a chainlike dimer phase, enabled by the ring‐flip of the cyclohexyl wingtip. Multiple methods including scanning tunneling microscopy (STM), X‐ray photoelectron spectroscopy (XPS) and density functional theo...

The in‐depth understanding of local atomic environment–property relationships of p‐block metal single‐atom catalysts toward the 2 e⁻ oxygen reduction reaction (ORR) has rarely been reported. Here, guided by first‐principles calculations, we develop a heteroatom‐modified In‐based metal–organic framework‐assisted approach to accurately synthesize an...

The in‐depth understanding of local atomic environment–property relationships of p‐block metal single‐atom catalysts toward the 2 e− oxygen reduction reaction (ORR) has rarely been reported. Here, guided by first‐principles calculations, we develop a heteroatom‐modified In‐based metal–organic framework‐assisted approach to accurately synthesize an...

Transition metal dichalcogenides (TMDCs) with 2H phase are expected to be the building blocks in next-generation electronics, however, suffered from electrical anisotropy, which is the basics for multi-terminal artificial synaptic devices, digital inverters, and anisotropic memtransistors that are highly desired in neuromorphic computing. Herein, t...

TiSe2 is a layered material exhibiting a commensurate (2×2×2) charge density wave (CDW) with a transition temperature of ∼200 K. Recently, incommensurate CDW in bulk TiSe2 draws great interest due to its close relationship with the emergence of superconductivity. Here, we report an incommensurate superstructure in monolayer TiSe2/CuSe/Cu(111) heter...

Self-assembly of cyclohexyl cyclic (alkyl)(amino)carbenes (cyCAAC) can be realized and reversibly switched from a close-packed trimer phase to a chainlike dimer phase, enabled by the ring-flip of the cyclohexyl wingtip. Multiple methods including scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and density functional theo...

The linkage structures between monomers make great influence on the properties of polymers. The synthesis of some special linkage structures can be challenging, which is often overcome by employing special reaction conditions. Here, we build dihydropentalene linkage in poly-naphthalocyanine on Ag(110) surface. Scanning tunneling microscopy (STM) an...

Ferroelectric (FE) materials possess electrically switchable spontaneous polarizations, showing broad applications in various functional devices. Call for the miniaturization of electronic devices, two-dimensional (2D) van der Waals (vdW) ferroelectric materials and the corresponding bulk counterpart trigger more interest of researchers. Recently,...

Two-dimensional (2D) materials with defects are desired for catalysis after the adsorption of monodispersed noble metal atoms. High-performance catalysts with the absolute value of Gibbs free energy (∣∆GH∣) close to zero, is one of the ultimate goals in the catalytic field. Here, we report the formation of monolayer titanium selenide (TiSe2) with l...

Since the advent of graphene ushered the era of 2D materials, many forms of hydrogenated graphene have been reported, exhibiting diverse properties ranging from a tunable bandgap to ferromagnetic ordering. Patterned hydrogenated graphene with micron‐scale patterns has been fabricated by lithographic means. Here, successful millimeter‐scale synthesi...

Functional molecules and their assemblies have attracted considerable attention arising from not only diverse structures with novel properties but also potential applications in molecular devices. The novel properties, which determine their applications, are strongly related to their structures. In recent years, benefiting from the development of a...

Discovery of novel two-dimensional (2D) ferroelectric materials and understanding the mechanism are of vital importance for the design of nanoscale ferroelectric devices. Herein, we report the distinct geometric evolution mechanism of the newly reported M2Ge2Y6 monolayers and find out a large group of 2D ferroelectric candidates based on this mecha...

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are emerging as new electrocatalysts and photocatalysts. The edge sites of 2D TMDs show high catalytic activity and are thus favored at the catalyst surface over TMD inert basal planes. However, 2D TMDs that predominantly expose edges are thermodynamically unfavorable, limiting the number...

Combining solution‐based and surface‐assisted synthesis, we demonstrate the first synthesis of NBN‐doped bis‐tetracene (NBN‐BT) and peri‐tetracene (NBN‐PT). The chemical structures are clearly elucidated by high‐resolution scanning tunneling microscopy (STM) in combination with noncontact atomic force microscopy (nc‐AFM). Scanning tunneling spectro...

Point defects in 1T″anisotropic ReSe2 offer many possibilities for defect engineering, which could endow this two-dimensional semiconductor with new functionalities, but have so far received limited attention. Here, we systematically investigate a full spectrum of point defects in ReSe2, including vacancies (VSe1-4), isoelectronic substitutions (OS...

Two-dimensional (2D) materials like graphene and h-BN usually show high thermal conductivity, which enables rich applications in thermal dissipation and nanodevices. Disorder, on the other hand, is often present in 2D materials. Structural disorder induces localization of electrons and phonons and alters the electronic, mechanical, thermal, and mag...

Two-dimensional monolayer copper selenide (CuSe) has been epitaxially grown and predicted to host the Dirac nodal line fermion (DNLF). However, the metallic state of monolayer CuSe inhibits the potential application of nanoelectronic devices in which a band gap is needed to realize on/off properties. Here, we engineer the band structure of monolaye...

Graphene nanoribbons with zigzag edges(ZGNRs) have attracted much attention for their spin-polarized edge states predicted more than 15 years ago. Since the ZGNRs are fabricated on metal substrates using molecular precursors, due to their strong coupling with metal substrates, experimental detection of the spin-polarized edge states is still diffic...

Graphene has afforded an ideal 2D platform for investigating a rich and fascinating behavior of Dirac fermions. Here, we develop a theoretical mechanism for manipulating the Dirac fermions in graphene, such as from type-I to type-II and type-III, by a top-down nanopatterning approach. We demonstrate that by selective chemical adsorption to pattern...

Combining solution-based and surface-assisted synthesis, we demonstrate here the first synthesis of NBN-doped bis -tetracene ( NBN-BT ) and peri -tetracene ( NBN-PT ). Unlike unstable all-carbon-based bis -tetracene and peri -tetracene, both NBN-BT and NBN-PT exhibit excellent stability under ambient conditions. The chemical structures of NBN-BT an...

Co 3 Sn 2 S 2 has attracted a lot of attention for its multiple novel physical properties, including topological nontrivial surface states, anomalous Hall effect, and anomalous Nernst effect. Vacancies, which play important roles in functional materials, have attracted increasing research attention. In this paper, by using density functional theory...

The iron-based superconductor is emerging as a promising platform for Majorana zero mode, which can be used to implement topological quantum computation. One of the most significant advances of this platform is the appearance of large vortex level spacing that strongly protects Majorana zero mode from other low-lying quasiparticles. Despite the adv...

The on-surface synthesis from predesigned organic precursors can yield graphene nanoribbons (GNRs) with atomically precise widths, edge terminations and dopants, which facilitate the tunning of their electronic structures. Here, we report the synthesis of novel sulfur-doped cove-edged GNRs (S-CGNRs) on Au(111) from a specifically designed precursor...

Since the advent of graphene ushered the era of two-dimensional materials, many forms of hydrogenated graphene have been reported, exhibiting diverse properties ranging from a tunable band gap to ferromagnetic ordering. Patterned hydrogenated graphene with micron-scale patterns has been fabricated by lithographic means. Here we report successful mi...

The structure of amorphous materials-continuous random networks (CRN) vs. CRN containing randomly dispersed crystallites-has been debated for decades. In two-dimensional (2D) materials, this question can be addressed more directly. Recently, controlled experimental conditions and atomic-resolution imaging found that monolayer amorphous carbon (MAC)...

The interfacial structures and interactions of two-dimensional (2D) materials on solid substrates are of fundamental importance for the fabrication and application of 2D materials. However, selection of a suitable solid substrate to grow 2D material, determination and control of the 2D material-substrate interface remain a big challenge due to the...

Van der Waals (vdW) heterojunctions constructed by vertical stacking two-dimensional transition metal dichalcogenides hold exciting promise in realizing future atomically thin electronic and optoelectronic devices. Recently, a Janus WSSe structure has been successfully synthesized by using chemical vapor deposition, selective epitaxy atomic replace...

Two-dimensional semiconductors (2DSCs) with appropriate band gaps and high mobilities are highly desired for future-generation electronic and optoelectronic applications. Here, using first-principles calculations, we report a novel class of 2DSCs, group-11-chalcogenide monolayers (M2X, M = Cu, Ag, Au; X = S, Se, Te), featuring with a broad range of...

Interfacial structures and interactions of two-dimensional (2D) materials on solid substrates are of fundamental importance for fabrications and applications of 2D materials. However, selection of a suitable solid substrate to grow a 2D material, determination and control of 2D material-substrate interface remain a big challenge due to the large di...

Monolayer CrN has been predicted to be half-metallic ferromagnet with high Curie temperature. Due to bulk CrN's biocompatibility, the monolayer is a promising candidate for bio-related devices. Here, using first-principles calculations based on density functional theory, we find that the formation energy of the bulk CrN stacking from layers with sq...

Nanographenes (NGs) can be embedded with predesigned dopants or nonhexagonal rings to tailor the electronic properties and provide ideal platforms to study the unique physical and chemical properties. Here, we report the on-surface synthesis of NBN-doped NG embedded with five- and seven-membered rings (NBN-575-NG) on Au(111) from a oligophenylene p...

A low-temperature ultra-high vacuum scanning probe microscopy (SPM) system with molecular beam epitaxy capability and optical access was conceived, built, and tested in our lab. The design of the whole system is discussed here, with special emphasis on some critical parts. We made an SPM scanner head with a modified Pan-type design, enclosed by a d...

Silicene is a promising 2D Dirac material as a building block for van der Waals heterostructures (vdWHs). Here we investigate the electronic properties of hexagonal boron nitride/silicene (BN/Si) vdWHs using first-principles calculations. We calculate the energy band structures of BN/Si/BN heterostructures with different rotation angles and find th...

Epitaxial growth on transition metal surfaces is an effective way to prepare large-area and high-quality graphene. However, the strong interaction between graphene and metal substrates suppresses the intrinsic excellent properties of graphene and the conductive metal substrates also hinder its applications in electronics. Here we demonstrate the de...

Braiding Majorana zero modes is essential for fault-tolerant topological quantum computing. Iron-based superconductors with nontrivial band topology have recently emerged as a surprisingly promising platform for creating distinct Majorana zero modes in magnetic vortices in a single material and at relatively high temperatures. The magnetic field-in...

As a new type of iron-based superconductor, CaKFe4As4 has recently been demonstrated to be a promising platform for observing Majorana zero modes (MZMs). The surface of CaKFe4As4 plays an important role in realizing the MZM since it hosts superconducting topological surface states. However, due to the complicated crystal structure, the terminal sur...

Two-dimensional (2D) materials with both auxetic effect and ferroelasticity are rare, however, have great potential applications in next generation microelectromechanical and nanoelectronic devices. Here, we report the findings of an extraordinary combination half-auxetic effect and ferroelasticity in a single p2mm-type TiSe monolayer by performing...

http://n04.iphy.ac.cn/allpdf/2021papers/Wu2021_Article_ConstructionOfPoly-naphthalocy.pdf ------------- Cyclic-conjugated linkages between planar-macrocyclic molecules contribute to the robustness of the two-dimensional (2D) polymerization and extension of π-interactions. The fabrication of such linkages in 2D polymers remains challenging. Combini...

We report an Ag1 single‐atom catalyst (Ag1/MnO2), which was synthesized from thermal transformation of Ag nanoparticles (NPs) and surface reconstruction of MnO2. The evolution process of Ag NPs to single atoms is firstly revealed by various techniques, including in situ ETEM, in situ XRD and DFT calculations. The temperature‐induced surface reconst...

Single-molecular devices show remarkable potential for applications in downscale electronic devices. The adsorption behavior of a molecule on a metal surface is of great importance from both fundamental and technological points of view. Herein, based on first-principles calculations, the adsorption of a 4,4″-diamino-p-terphenyl (DAT) molecule on a...

Graphene on SiO2 enables fabrication of Si-technology-compatible devices, but a transfer of these devices from other substrates and direct growth have severe limitations due to a relatively small grain size or device-contamination. Here, we show an efficient, transfer-free way to integrate centimeter-scale, single-crystal graphene, of a quality sui...

Silver nanoparticles converted into single atoms bring about a significant improvement in electrocatalytic CO2 reduction with a 95.7 % faradic efficiency for CO production. Abstract We report an Ag1 single‐atom catalyst (Ag1/MnO2), which was synthesized from thermal transformation of Ag nanoparticles (NPs) and surface reconstruction of MnO2. The e...

Recent years have witnessed tremendous success in the discovery of topological states of matter. Particularly, sophisticated theoretical methods in time-reversal-invariant topological phases have been developed, leading to the comprehensive search of crystal database and the prediction of thousands of topological materials. In contrast, the discove...

Iron-chalcogenide superconductors have emerged as a promising Majorana platform for topological quantum computation. By combining topological band and superconductivity in a single material, they provide significant advantage to realize isolated Majorana zero modes. However, iron-chalcogenide superconductors, especially Fe(Te,Se), suffer from stron...