Recently, new states of matter like superconducting or topological quantum states were found in transition metal dichalcogenides (TMDs) and manifested themselves in a series of exotic physical behaviors. Such phenomena have been demonstrated to exist in a series of transition metal tellurides including MoTe2, WTe2 and alloyed MoxW1-xTe2. However, the behaviors in the alloy system have been rarely addressed due to their difficulty in obtaining atomic layers with controlled composition, albeit the alloy offers a great platform to tune the quantum states. Here, we report a facile CVD method to synthesize the MoxW1-xTe2 with controllable thickness and chemical composition ratios. The atomic structure of monolayer MoxW1-xTe2 alloy was experimentally confirmed by scanning transmission electron microscopy (STEM). Importantly, two different transport behaviors including superconducting and Weyl semimetal (WSM) states were observed in Mo-rich Mo0.8W0.2Te2 and W-rich Mo0.2W0.8Te2 samples respectively. Our results show that the electrical properties of MoxW1-xTe2 can be tuned by controlling the chemical composition, demonstrating our controllable CVD growth method is an efficient strategy to manipulate the physical properties of TMDCs. Meanwhile, it provides a perspective on further comprehension and shed light on the design of device with topological multicomponent TMDCs materials.
Emergent grain boundaries at free surface control material properties such as nanomaterial strength, catalysis, and corrosion. Recently the restructuring of emergent boundaries on copper (111) surfaces was discovered experimentally and atomic calculations point to its universality in fcc metal systems. Restructuring is due to a preference for boundaries to shift their tilt axis across the (1-10) plane towards [112] and ultimately to form low energy [112] core shifted boundaries (CSBs). However, the observed geometry of these emergent boundaries is not reproduced by atomic calculations and the …
Large-area MoS2 atomic layers are synthesized on SiO2 substrates by chemical vapor deposition using MoO3 and S powders as the reactants. Optical, microscopic and electrical measurements suggest that the synthetic process leads to the growth of MoS2 monolayer. The TEM images verify that the synthesized MoS2 sheets are highly crystalline.
Emergent behavior at complex oxide interfaces has driven much of the research in the oxide thin film community for the past twenty years. Interfaces have been engineered for potential applications in spintronics, topological quantum computing, and high-speed electronics in cases where the bulk materials would not exhibit the desired properties. Advances in thin film growth have made the synthesis of these interfaces possible, while surface characterization tools such as X-ray photoelectron spectroscopy have been critical to understanding surface and interfacial phenomena in these materials. In…
Monochalcogenides of germanium (or tin) are considered as stable isoelectronic and isostructural analogue of black phosphorous. Their two-dimensional (2D) forms have been just predicted to shown strong thickness-dependent physical properties, and even indirect to direct band gap crossover at the monolayer limit. Here, we demonstrate the synthesis of atomically thin GeSe by direct sonication-assisted exfoliation of bulk microcrystalline powders in solvents. The exfoliated few-layer GeSe sheets characterize high crystallinity with lateral sizes over 100 nm and, importantly, strong resistance aga…
The formation of a 3D network composed of free standing and interconnected Pt nanowires is achieved by a two-step method, consisting of conformal deposition of Pt by atomic layer deposition (ALD) on a forest of carbon nanotubes and subsequent removal of the carbonaceous template. Detailed characterization of this novel 3D nanostructure was carried out by transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS). These characterizations showed that this pure 3D nanostructure of platinum is self-supported and offers an enhancement of the electrochemically active sur…
Highly ordered and self supported anatase TiO2 nanoparticle chains were fabricated by calcining conformally TiO2 coated multi-walled carbon nanotubes (MWCNTs). During annealing, the thin tubular TiO2 coating that was deposited onto the MWCNTs by atomic layer deposition (ALD) was transformed into chains of TiO2 nanoparticles (~12 nm diameter) with an ultrahigh surface area (137 cm2 per cm2 of substrate), while at the same time the carbon from the MWCNTs was removed. Photocatalytic tests on the degradation of acetaldehyde proved that these forests of TiO2 nanoparticle chains are highly photo act…
Autonomous epitaxial atomic-layer synthesis via real-time computer vision of electron diffraction
University of Maryland, College Park（马里兰大学帕克分校）；Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park（马里兰大学帕克分校物理系马里兰量子材料中心）；Institute for Solid State Physics, University of Tokyo（东京大学固体物理研究所）；U.S. Naval Research Laboratory（美国海军研究实验室）；National Institute of Standards and Technology（美国国家标准与技术研究院）
Hydrogen-rich superhydrides are believed to be very promising high-Tc superconductors as they are expected to mimic characteristics of metallic hydrogen. Recent experiments discovered superhydrides at very high pressures, e.g. FeH5 at 130 GPa and LaH10 at 170 GPa. With the motivation of discovering new hydrogen-rich high-Tc superconductors at lowest possible pressure, here we report the prediction and experimental synthesis of cerium superhydride CeH9 below 100 GPa in the laser-heated diamond anvil cell. Ab-initio calculations were carried to evaluate the detailed chemistry of the Ce-H system …
Single layered molybdenum disulfide with a direct bandgap is a promising two-dimensional material that goes beyond graphene for next generation nanoelectronics. Here, we report the controlled vapor phase synthesis of molybdenum disulfide atomic layers and elucidate a fundamental mechanism for the nucleation, growth, and grain boundary formation in its crystalline monolayers. Furthermore, a nucleation-controlled strategy is established to systematically promote the formation of large-area single- and few-layered films. The atomic structure and morphology of the grains and their boundaries in th…
Technical University of Denmark（丹麦技术大学）；University of Oxford（牛津大学）；IT University of Copenhagen（哥本哈根信息技术大学）；University of Copenhagen（哥本哈根大学）；Aarhus University（奥胡斯大学）；Columbia University（哥伦比亚大学）；Lund University（隆德大学）
Atomic-scale materials synthesis via layer deposition techniques present a unique opportunity to control material structures and yield systems that display unique functional properties that cannot be stabilized using traditional bulk synthetic routes. However, the deposition process itself presents a large, multidimensional space that is traditionally optimized via intuition and trial and error, slowing down progress. Here, we present an application of deep reinforcement learning to a simulated materials synthesis problem, utilizing the Stein variational policy gradient (SVPG) approach to trai…
Kawamura et. al. recently published an article about the synthesis of rhenium nitride with MoS2-type structure [APL 100, 251910(2012)]. We disagree with the composition proposed by Kawamura. The compound synthesized by Kawamura is ReN3, or a compound of similar composition. What Kawamura did is to find the Re atomic positions of a compound where the nitrogen concentration remains unknown. This paper was rejected form APL. The reviewer comments (and our reply) are included here.
Altermagnetic Signatures and Topological Textures in Ultrathin Multiferroic BiFeO$_3$
Brown University（布朗大学）；Cornell University（康奈尔大学）；Rice University（莱斯大学）；Rice Advanced Materials Institute, Rice University（莱斯大学先进材料研究所）；MAX IV Laboratory（MAX IV实验室）；University of Arkansas（阿肯色大学）；Johannes Gutenberg-University Mainz（美因茨约翰内斯·古腾堡大学）；Oak Ridge National Laboratory（橡树岭国家实验室）；Max Planck Institute for the Physics of Complex Systems（马克斯·普朗克复杂系统物理研究所）；University of Augsburg（奥格斯堡大学）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；University of California, Berkeley（加州大学伯克利分校）；Tel Aviv University（特拉维夫大学）；Max Planck Institute for Chemical Physics of Solids（马克斯·普朗克固体化学物理研究所）；Czech Academy of Sciences（捷克科学院）；Kavli Institute at Cornell for Nanoscale Science, Cornell University（康奈尔纳米科学卡弗里研究所）；Leibniz-Institut für Kristallzüchtung（莱布尼兹晶体生长研究所）；Smalley-Curl Institute, Rice University（莱斯大学斯莫利-柯尔研究所）；Northeastern University（东北大学）
We report the atomic layer deposition of titanium dioxide on carbon nanosheet templates and investigate the effects of post-deposition annealing in a helium environment using different characterization techniques. The crystallization of the titanium dioxide coating upon annealing is observed using in-situ X-ray diffraction. The (micro)-structural characterization of the films is carried out by scanning electron microscopy and advanced transmission electron microscopy techniques. Our study shows that the annealing of the atomic layer deposition processed and carbon nanosheets templated titanium…
The challenge of synthesizing graphene nanoribbons (GNRs) with atomic precision is currently being pursued along a one-way road, based on the synthesis of adequate molecular precursors that react in predefined ways through self-assembly processes. The synthetic options for GNR generation would multiply by adding a new direction to this readily successful approach, especially if both of them can be combined. We show here how GNR synthesis can be guided by an adequately nanotemplated substrate instead of by the traditionally designed reactants. The structural atomic precision, unachievable to da…
Phosphorene is a new two-dimensional material composed of a single or few atomic layers of black phosphorus. Phosphorene has both an intrinsic tunable direct band gap and high carrier mobility values, which make it suitable for a large variety of optical and electronic devices. However, the synthesis of single-layer phosphorene is a major challenge. The standard procedure to obtain phosphorene is by exfoliation. More recently, the epitaxial growth of single-layer phosphorene on Au(111) has been investigated by molecular beam epitaxy and the obtained structure has been described as a blue-phosp…
Emergent gold-induced interfacial magnetism in monolayer FePS$_3$
European Synchrotron Radiation Facility（欧洲同步辐射装置）；Université Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL（格勒诺布尔阿尔卑斯大学、法国国家科学研究中心、格勒诺布尔理工学院、NEEL研究所）；Department of Physics Giuseppe Occhialini, University of Milano-Bicocca（米兰比可卡大学朱塞佩·奥基亚利尼物理系）；Université Grenoble Alpes, CEA, IRIG, MEM（格勒诺布尔阿尔卑斯大学、法国原子能和替代能源委员会、研究与信息技术部、材料与物理化学实验室）
The incorporation of impurities during the chemical synthesis of nanomaterials is usually uncontrolled and rarely reported because of the formidable challenge that constitutes measuring trace amounts of often light elements with sub nanometre spatial resolution. Yet these foreign elements influence functional properties, by e.g. doping. Here we demonstrate how the synthesis and partial reduction reaction on hollow TiO2 nanowires leads to the introduction of parts-per-millions of boron, sodium, and nitrogen from the reduction reaction with sodium borohydride at the surface of the TiO2 nanowire.…
Controlling hydrocarbon transport and electron beam induced deposition on single layer graphene: toward atomic scale synthesis in the scanning transmission electron microscope
Despite recent successes in the synthesis of boron nanotubes (BNTs), the atomic arrangement of their walls has not yet been determined and many questions about their basic properties do remain. Here, we unveil the dynamical stability of BNTs by means of first-principles molecular dynamics simulations. We find that free-standing, single-wall BNTs with diameters larger than 0.6 nm are thermally stable at the experimentally reported synthesis temperature of 870$^\circ$C and higher. The walls of thermally stable BNTs are found to have a variety of different mixed triangular-hexagonal morphologies.…
Only a few of the vast range of potential two-dimensional materials have been isolated or synthesised to date. Typically, 2D materials are discovered by mechanically exfoliating naturally occurring bulk crystals to produce atomically thin layers, after which a material-specific vapour synthesis method must be developed to grow interesting candidates in a scalable manner. Here we show a general approach for synthesising thin layers of two-dimensional binary compounds. We apply the method to obtain high quality, epitaxial MoS2 films, and extend the principle to the synthesis of a wide range of o…
College of Physics, Chengdu University of Technology（成都理工大学物理学院）；Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford（牛津大学化学系物理与理论化学实验室）；Laboratoire Charles Coulomb (L2C), University of Montpellier and CNRS（蒙彼利埃大学与法国国家科学研究中心夏尔·库隆实验室）
The boson peak (BP) is a universal feature in the Raman and inelastic scattering spectra of both disordered and crystalline materials. The current paradigm presents the boson peak as the result of a Ioffe-Regel crossover between ballistic (phonon) and diffusive-type excitations, where the loss of coherence of phonons is described as a purely harmonic process due to structural disorder. This "harmonic disorder" paradigm for the BP has never been challenged or tested at the atomistic level. Here, through a set of atomistically-resolved characterizations of amorphous metallic alloys, we uncover a…
Establishing Atomic Coherence in Twisted Oxide Membranes Containing Volatile Elements
Oak Ridge National Laboratory（橡树岭国家实验室）；North Carolina State University（北卡罗来纳州立大学）；Sungkyunkwan University（成均馆大学）；Institute for Basic Science（基础科学研究院）；Duke University（杜克大学）
University of Texas at Austin（德克萨斯大学奥斯汀分校）；Pennsylvania State University（宾夕法尼亚州立大学）；University of Texas at Dallas（德克萨斯大学达拉斯分校）；Oden Institute for Computational Engineering and Sciences, University of Texas at Austin（德克萨斯大学奥斯汀分校奥登计算工程与科学研究所）；National Yang Ming Chiao Tung University (NYCU)（国立阳明交通大学）
Graphene and carbon nanotubes (CNTs) share the same atomic structure of hexagonal carbon lattice. Yet, their synthesis differs in many aspects, including the shape and size of the catalyst. Here, we demonstrate a floating-catalyst chemical vapor deposition (FCCVD) technique for substrate-free, single-step growth of CNT-graphene heterostructures (CNT-G-H) using ethylene as a carbon source. The formation of CNT-G-H is directly evidenced by lattice-resolved (scanning) transmission electron microscopy (STEM) and electron diffraction experiments, corroborated by atomic force microscopy (AFM). Our e…
Imposing additional confinement in two-dimensional (2D) materials can yield further control over the associated electronic, optical, and topological properties. However, synthesis of ultra-narrow nanoribbons (NRs) remains a challenge, particularly for the transition metal dichalcogenides (TMDs), and synthesizing TMD NRs narrower than 50 nm has remained elusive. Here, we report the vapor-phase synthesis of ultra-narrow TaS2 NRs. The NRs are grown within the hollow cavity of carbon nanotubes, thereby limiting their lateral dimensions and layer number, while simultaneously stabilizing them agains…
Benchmarking large language models for materials synthesis: the case of atomic layer deposition
Applied Materials Division, Argonne National Laboratory（阿贡国家实验室应用材料部门）；Business and Information Systems, Argonne National Laboratory（阿贡国家实验室商业与信息系统部门）；Northwestern Center for Water Research, Northwestern University（西北大学水研究中心）
Shape-controlled synthesis of multiply twinned nanostructures is heavily emphasized in nanoscience, in large part due to the desire to control the size, shape, and terminating facets of metal nanoparticles for applications in catalysis. Direct control of the size and shape of solution-grown nanoparticles relies on an understanding of how synthetic parameters alter nanoparticle structures during synthesis. However, while outcome populations can be effectively studied with standard electron microscopy methods, transient structures that appear during some synthetic routes are difficult to study u…
Advances in synthesis techniques and materials understanding have given rise to oxide heterostructures with intriguing physical phenomena that cannot be found in their constituents. In these structures, precise control of interface quality, including oxygen stoichiometry, is critical for unambiguous tailoring of the interfacial properties, with deposition of the first monolayer being the most important step in shaping a well-defined functional interface. Here, we studied interface formation and strain evolution during the initial growth of LaAlO3 on SrTiO3 by pulsed laser deposition, in search…
