Xiao Tong

Xiao Tong
Brookhaven National Laboratory · Center for Functional Nanomaterials

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214
Publications
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Publications

Publications (214)
Article
We evaluate the material characteristics of superconducting platinum silicide (PtSi) thin films as candidate materials for superconducting quantum information devices compatible with silicon technology. These films were synthesized using magnetron sputtering under ultrahigh vacuum conditions, followed by rapid thermal annealing. Polycrystalline PtS...
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Here, by using angle-resolved photoemission spectroscopy, we showed that Bi2−xCrxSe3 single crystals have a distinctly well-defined band structure with a large bulk band gap and undistorted topological surface states. These spectral features are unlike their thin film forms in which a large nonmagnetic gap with a distorted band structure was report...
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Periodic lattice distortion, known as the charge density wave, is generally attributed to electron–phonon coupling. This correlation is expected to induce a pseudogap at the Fermi level in order to gain the required energy for stable lattice distortion. The transition metal dichalcogenide 1T-VSe2 also undergoes such a transition at 110 K. Here, we...
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LiNi0.8Mn0.1Co0.1O2 (NMC811) is an important Li-ion battery cathode material; however, there is a tradeoff between delivered capacity and capacity retention. As the charge potential increases the capacity rises but at the expense of capacity retention. The decrease in capacity retention has been ascribed to several factors including particle cracki...
Preprint
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The electronic origin of the structural transition in 1T-VSe$_2$ is re-evaluated through an extensive angle-resolved photoemission spectroscopy experiment. The components of the band structure, missing in previous reports, are revealed. Earlier observations, shown to be temperature independent and therefore not correlated with the phase transition,...
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Metal phosphide-containing materials have emerged as a potential candidate of nonprecious metal-based catalysts for alkaline oxygen evolution reaction (OER). While it is known that metal phosphide undergoes structural evolution, considerable debate persists regarding the effects of dynamics on the surface activation and morphological stability of t...
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Facilitating widespread adoption of electric vehicles will require next-generation battery systems that can operate reliably over a large temperature range, at high operating voltage, and under fast charging rates. Herein, a novel class of nonflammable fluorinated ester-based local high concentration electrolytes (LHCEs) are described. When cycled...
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Scaling up superconducting quantum circuits based on transmon qubits necessitates substantial enhancements in qubit coherence time. Over recent years, tantalum (Ta) has emerged as a promising candidate for transmon qubits, surpassing conventional counterparts in terms of coherence time. However, amorphous surface Ta oxide layer may introduce dielec...
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Surfactants are widely used in the synthesis of nanoparticles, as they have a remarkable ability to direct their growth to obtain well-defined shapes and sizes. However, their post-synthesis removal is a challenge, and the methods used often result in morphological changes that defeat the purpose of the initial controlled growth. Moreover, after th...
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Delafossite-phase CuAlO 2 and CuFeO 2 thin film photocathodes were developed for solar water splitting, with CuFeO 2 showing higher efficiency due to improved light absorption.
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Surfactants are widely used in the synthesis of nanoparticles, as they have a remarkable ability to direct their growth to obtain well-defined shapes and sizes. However, their post-synthesis removal is a challenge, and the methods used often result in morphological changes that defeat the purpose of the initial controlled growth. The cleaning metho...
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The zeolitic-imidazolate-framework-8 (ZIF-8) is one of the extensively studied metal-organic frameworks (MOF) materials because of its unique structure. For its potential applicability in numerous fields, it becomes crucial to have detailed studies on the structural stability of ZIF-8, especially in aqueous environments. A number of studies have be...
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Kinetic Monte Carlo (kMC) simulations along with density functional theory (DFT) calculations were used to investigate the aggregation of size-selected Nb3Oy (y = 5, 6, 7) clusters deposited onto the Au(111) surface. Recent STM experiments showed that the cluster binding sites and sizes of the cluster assemblies on the Nb3Oy/Au(111) surfaces strong...
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The two degenerate valleys in transition metal dichalcogenides can be used to store and process information for quantum information science and technology. A major challenge is maintaining valley polarization at room temperature where phonon-induced intervalley scattering is prominent. Here we demonstrate room temperature valley polarization in het...
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To develop graphene-based nanomaterials as reliable catalysts for electrochemical energy conversion and storage systems (e.g. PEM fuel cells, metal–air batteries, etc.), it is imperative to critically understand their performance changes and correlated material degradation processes under different operational conditions. In these systems, hydrogen...
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We report a study of selenospinel Cu$_{6-x}$Fe$_{4+x}$Sn$_{12}$Se$_{32}$ ($x$ = 0, 1, 2) single crystals, which crystalize in a cubic structure with the $Fd\overline{3}m$ space group, and show typical semiconducting behavior. The large discrepancy between the activation energy for electrical conductivity $E_\rho$ (32.3 $\sim$ 69.8 meV), and for the...
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We report a study of selenospinel Cu 6−x Fe 4+x Sn 12 Se 32 (x = 0, 1, 2) single crystals, which crystallize in a cubic structure with the F d3m space group, and show typical semiconducting behavior. The large discrepancy between the activation energy for electrical conductivity E ρ (32.3-69.8 meV), and for thermopower E S (3.2-11.5 meV), indicates...
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In this study, the thermal stability of Au-Al2O3 core-shell and Au nanowires was investigated by in situ scanning transmission electron microscopy and other techniques. The nanowires were synthesized by the helium droplets method and deposited on various substrates. The in situ characterization of Au-Al2O3 thermal stability demonstrated a substanti...
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Healthcare systems worldwide have been stressed to provide sufficient resources to serve the increasing and aging population in our society. The situation became more challenging at the time of pandemic. Technology advancement, especially the adoption of wearable health monitoring devices, has provided an important supplement to current clinical eq...
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Despite much technical progress achieved so far, the exact surface and shape evolution during wet chemical etching is less unraveled, especially in ionically bonded ceramics. Herein, by using in situ liquid cell transmission electron microscopy, a repeated two-stage anisotropic and pulsating periodic etching dynamic is discovered during the pencil...
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The sp-hybridized carbon chain (carbyne) is a representative 1D atomic material, whose bonding structure and chemical reactivity have remained a mystery for a century. Here, we report the unexpected alternating bond orders of 1.4 and 2.6 for the most stable carbon chain and the in situ diffuse reflectance infrared Fourier-transform spectroscopy (DR...
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Two-dimensional (2D) siloxene (Si6O3H6) has shown promise as a negative electrode material for Li-ion batteries due to its high gravimetric capacity and superior mechanical properties under (de)lithiation compared to bulk Si. In this work, we prepare purified siloxene nanosheets through the removal of bulk Si contaminants, use ultrasonication to co...
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Topological semimetals such as Dirac, Weyl or nodal line semimetals are widely studied for their peculiar properties including high Fermi velocities, small effective masses and high magnetoresistance. When the Dirac cone is tilted, exotic phenomena could emerge whereas materials hosting such states are promising for photonics and plasmonics applica...
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The syntheses of FeS 2 and Fe 3 S 4 nanomaterials were optimized using a novel facile, surfactant-free, and microwave-assisted, one-pot synthesis method, run under ambient and reasonably mild reaction conditions. Synthetic parameters, such as metal precursor salt identity, reaction time, reaction temperature, metal:sulfur molar ratios, and solvent...
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How surface chemistry influences reactions occurring thereupon has been a long-standing question of broad scientific and technological interest. Here, we consider the relation between the surface chemistry at interfaces and the reversibility of electrochemical transformations at rechargeable battery electrodes. Using Zn as a model system, we report...
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Alkali antimonide photocathodes have wide applications in free-electron lasers and electron cooling. The short lifetime of alkali antimonide photocathodes necessitates frequent replacement of the photocathodes during a beam operation. Furthermore, exposure to mediocre vacuum causes loss of photocathode quantum efficiency due to the chemical reactio...
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We probe the adsorption of molecular H2O on a TiO2 (110)-(1 × 1) surface decorated with isolated VO clusters using ultrahigh-vacuum scanning tunneling microscopy (UHV-STM) and temperature-programmed desorption (TPD). Our STM images show that preadsorbed VO clusters on the TiO2 (110)-(1 × 1) surface induce the adsorption of H2O molecules at room tem...
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Charge density waves (CDWs) with superconductivity, competing Fermi surface instabilities and collective orders, have captured much interest in two-dimensional van der Waals (vdW) materials. Understanding of CDW suppression mechanism, its connection to emerging superconducting state and electronic correlations provides opportunities for engineering...
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Charge density waves (CDWs) with superconductivity, competing Fermi surface instabilities, and collective orders have captured much interest in two-dimensional van der Waals (vdW) materials. Understanding the CDW suppression mechanism, its connection to the emerging superconducting state, and electronic correlations provides opportunities for engin...
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Silicon (Si) anodes are promising candidates for Li-ion batteries due to their high specific capacity and low operating potential. Implementation has been challenged by the significant Si volume changes during (de)lithiation and associated growth/regrowth of the solid electrolyte interface (SEI). In this report, fluorinated local high concentration...
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Two-dimensional magnetic materials (2DMM) are significant for studies on the nature of 2D long range magnetic order but also for future spintronic devices. Of particular interest are 2DMM where spins can be manipulated by electrical conduction. Whereas Cr$_2$Si$_2$Te$_6$ exhibits magnetic order in few-layer crystals, its large band gap inhibits ele...
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Two-dimensional magnetic materials (2DMMs) are significant not only for studies on the nature of 2D long-range magnetic order but also for future spintronic devices. Of particular interest are 2DMMs where spins can be manipulated by electrical conduction. Whereas Cr 2 Si 2 Te 6 exhibits magnetic order in few-layer crystals, its large band gap inhib...
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As an inexpensive and naturally abundant two-dimensional (2D) material, molybdenum disulfide (MoS2) exhibits a high Li-ion storage capacity along with a low volume expansion upon lithiation, rendering it an alternative anode material for lithium-ion batteries (LIBs). However, the challenge of using MoS2-based anodes is their intrinsically low elect...
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Herein, we investigate the effect of the chemical composition of double perovskite nanorods on their versatile electrocatalytic activity not only as supports for the oxidation of small organic molecules but also as catalysts for the oxygen evolution reaction. Specifically, Y2CoMnO6 and Y2NiMnO6 nanorods with average diameters of 300 nm were prepare...
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Oxidation is a corrosion reaction where the corroded metal forms an oxide. Prevention of oxidation at the nanoscale is critically important to retain the physicochemical properties of metal nanoparticles. In this work, we studied the stability of polyethylene glycol (PEG) coated copper nanoparticles (PEGylated CuNPs) against oxidation. The freshly-...
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Atomically dispersed single-atom catalysts have the potential to bridge heterogeneous and homogeneous catalysis. Dozens of single-atom catalysts have been developed, and they exhibit notable catalytic activity and selectivity that are not achievable on metal surfaces. Although promising, there is limited knowledge about the boundaries for the monom...
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This study thoroughly investigated the synthesis of not only 4 triply-doped metal oxides but also 5 singly-doped analogues of Li4Ti5O12 for electrochemical applications. In terms of synthetic novelty, the triply-doped materials were fabricated using a relatively facile hydrothermal method for the first-time, involving the simultaneous substitution...
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Silicon (Si) is a promising high-capacity material for lithium-ion batteries; however, its limited reversibility hinders commercial adoption. Approaches such as particle and crystallite size reduction, introduction of conductive carbon, and use of different electrolyte solvents have been explored to overcome these electrochemical limitations. Herei...
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The mechanical degradation experienced by Si electrodes during Li (de)alloying reactions can potentially be mitigated by using Si‐based materials with layered 2D geometries. Such materials are expected to exhibit favorable mechanical properties and be capable of buffering the volume change associated with (de)lithitation. In this work, 2D siloxene...
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Modulation of electron/ion transport in electrodes through the appropriate mesoscale electrode structural design is essential to achieving effective utilization of nanoscale electroactive materials. Herein, nanosheet MoS2+x/carbon [one-dimensional (1D) carbon nanotube (CNT) or two-dimensional (2D) graphene nanoplatelet (GNP)] heterostructures are p...
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How surface chemistry influences reactions occurring thereupon has been a long-standing question of broad scientific and technological interest for centuries. Recently, it has re-emerged as a critical question in a subdiscipline of chemistry - electrochemistry at heterointerphases, where the answers have implications for both how, and in what forms...
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We report a detailed study of electrical and thermal transport properties in 2H-M$_x$TaS$_2$ (M = Mn, Co) magnets where M atoms are intercalated in the van der Waals gap. The intercalation induces ferromagentism with an easy-plane anisotropy in 2H-Mn$_x$TaS$_2$, but ferromagnetism with a strong uniaxial anisotropy in 2H-Co$_{0.22}$TaS$_2$, which fi...
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Two-dimensional transition metal trichalcogenides (TMTC's) feature covalently bonded metal-chalcogen layers separated by the van der Waals (vdW) gap. Similar to transition metal dichalcogenides (TMDCs), TMTCs often host charge density waves (CDWs) and superconductivity but unlike TMDCs atomic chains in the crystal structure give rise to quasi one-d...
Article
Alloy oxidation is complex and involves several critical processes that lack understanding on the atomic level. Here, we report an atomistic picture of the initial-stage oxidation of stepped Cu3Au(100) using a combination of surface science tools and modeling to illuminate the microscopic processes underlying oxygen-adsorption-induced structural an...
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We report a detailed study of electrical and thermal transport properties in 2H−MxTaS2 (M=Mn, Co) magnets where M atoms are intercalated in the van der Waals gap. The intercalation induces ferromagnetism (FM) with an easy-plane anisotropy in 2H−MnxTaS2, but FM with a strong uniaxial anisotropy in 2H−Co0.22TaS2, which finally evolves into a three-di...
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Two-dimensional transition metal trichalcogenides (TMTCs) feature covalently bonded metal-chalcogen layers separated by the van der Waals (vdW) gap. Similar to transition metal dichalcogenides (TMDCs), TMTCs often host charge density waves (CDWs) and superconductivity, but unlike TMDCs, atomic chains in the crystal structure give rise to quasi one-...
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We have correlated the performance of double perovskite metal oxides as support media for the methanol oxidation reaction (MOR) with their intrinsic size, shape, and composition.
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Transition metal dichalcogenides attract considerable attention due to a variety of interesting properties, including long-range magnetism in nanocrystals. Here we investigate the magnetic, thermal, and electrical properties of an FeTe2 single crystal with iron vacancy defects. Magnetic measurements show a paramagnetic state and the absence of magn...
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Photoelectrochemical (PEC) water splitting is typically studied at room temperature. In this work, the temperature effect on PEC water splitting is studied using crystalline BiVO4 thin film photoanode as a model system. Systematic temperature-dependent electrochemical study demonstrates that the PEC activity is boosted at elevated electrolyte tempe...
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Ni-rich NMC is an attractive Li-ion battery cathode due to its combination of energy density, thermal stability, and reversibility. While higher delivered energy density can be achieved with a more positive charge voltage limit, this approach compromises sustained reversibility. Improved understanding of the local and bulk structural transformation...
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Due to their exceptional catalytic properties for the oxygen reduction reaction (ORR) and other crucial electrochemical reactions, PtCo intermetallic nanoparticle (NP) and single atomic (SA) Pt metal site catalysts have received considerable attention. However, their formation mechanisms at the atomic level during high-temperature annealing process...
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α-MnO2 type materials have been studied as electrode materials in rechargeable batteries and electrocatalysts due to their 2 × 2 tunneled crystal structures capable of accommodating cations and their tunable physiochemical properties. In this study, we deliberately synthesized K+ containing α-MnO2 (K0.9Mn8O16) hollow nanotubes varying the dimension...
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Thin-film solid-state interfacial dealloying (thin-film SSID) is an emerging technique to design nanoarchitecture thin films. The resulting controllable 3D bicontinuous nanostructure is promising for a range of applications including catalysis, sensing, and energy storage. Using a multiscale microscopy approach, we combine X-ray and electron nano-t...