記述言語：英語   出版者・発行元：Scientific Reports  

We examine the effect of isovalent substitutions and co-doping on the ionic dielectric constant of paraelectric titanates (perovskite, Ruddlesden-Popper phases, and rutile) using density functional perturbation theory. Substitutions increase the ionic dielectric constant of the prototype structures, and new dynamically stable structures with εion ~ 102–104 are reported and analyzed. The boosting of ionic permittivity is attributed to local defect-induced strain, and maximum Ti–O bond length is proposed as a descriptor. The Ti–O phonon mode that is responsible for the large dielectric constant can be tuned by a local strain and symmetry lowering from substitutions. Our findings help explain the recently observed colossal permittivity in co-doped rutile, attributing its intrinsic permittivity boosting solely to the lattice polarization mechanism, without the need to invoke other mechanisms. Finally, we identify new perovskite- and rutile-based systems that can potentially display colossal permittivity.

DOI： 10.1038/s41598-023-30965-6

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記述言語：英語   出版者・発行元：Journal of the American Chemical Society  

Two-dimensional transition metal dichalcogenides (TMD), such as molybdenum disulfide (MoS2), have aroused substantial research interest in recent years, motivating the quest for new synthetic strategies. Recently, halide salts have been reported to promote the chemical vapor deposition (CVD) growth of a wide range of TMD. Nevertheless, the underlying promoting mechanisms and reactions are largely unknown. Here, we employ first-principles calculations and ab initio molecular dynamics (AIMD) simulations in order to investigate the detailed molecular mechanisms during the salt-assisted CVD growth of MoS2monolayers. The sulfurization of molybdenum oxyhalides MoO2X2(X = F, Cl, Br, and I)-the form of Mo-feedstock dominating in salt-assisted synthesis-has been explored and displays much lower activation barriers than that of molybdenum oxide present during conventional "saltless" growth of MoS2. Furthermore, the rate-limiting barriers appear to depend linearly on the electronegativity of the halogen element, with oxyiodide having the lowest barrier. Our study reveals the promoting mechanisms of halides and allows growth parameter optimization to achieve even faster growth of MoS2monolayers in the CVD synthesis.

DOI： 10.1021/jacs.2c02497

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記述言語：英語   出版者・発行元：Nano Letters  

Electron optics is the systematic use of electromagnetic (EM) fields to control electron motions. In graphene, strain induces pseudo-electromagnetic fields to guide electron motion. Here we demonstrate the use of substrate topography to impart desirable strain on graphene to induce static pseudo-EM fields. We derive the quasi-classical equation of motion for Dirac Fermions in a pseudo-EM field in graphene and establish the correspondence between the quasi-classical and quantum mechanical snake states. Based on the trajectory analysis, we design sculpted substrates to realize various "optical devices" such as a converging lens or a collimator, and further propose a setup to achieve valley Hall effect solely through substrate patterning, without any external fields, to be used in valleytronics applications. Finally, we discuss how the predicted strain/pseudo-EM field patterns can be experimentally sustained by typical substrates and generalized to other 2D materials.

DOI： 10.1021/acs.nanolett.2c00103

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記述言語：英語   出版者・発行元：Nanoscale Advances  

Two-dimensional metals offer intriguing possibilities to explore the metallic and other related properties in systems with reduced dimensionality. Here, following recent experimental reports of synthesis of two-dimensional metallic gallium (gallenene) on insulating substrates, we conduct a computational search of gallenene structures using the Particle Swarm Optimization algorithm, and identify stable low energy structures. Our calculations of the critical temperature for conventional superconductivity yield values of ∼7 K for gallenene. We also emulate the presence of the substrate by introducing the external confining potential and test its effect on the structures with unstable phonons. This journal is

DOI： 10.1039/d1na00553g

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出版者・発行元：Matter  

Metal corrosion from exposure to supercritical fluids is a long-standing challenge lacking atomistic understanding for effective corrosion prevention in diverse important applications. Here, reactions relevant to corrosion in supercritical CO2 (sCO2), with H2O and NO2 as impurities, are revealed using ab initio molecular dynamics and enhanced sampling methods. While little reactivity is observed in bulk sCO2, the iron surface is found to play a crucial almost-catalytic role in its own corrosion, activating the inert CO2 and hence facilitating ∗HCO3− and ∗CO32− formation at the interface. Moreover, the hydrogen bond network of ∗H2O assists the H shuttling to the activated CO2 and impurities, forming reactive species observed in experiments. Such atomistic insight elucidates the reaction mechanisms of metal corrosion in aqueous and supercritical fluids and can point to possible remedies.

DOI： 10.1016/j.matt.2021.12.019

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出版者・発行元：Carbon  

Graphite, with many industrial applications, is one of the widely sought-after allotropes of carbon. Although the geometric design of the graphite in many of the applications could dictate its precision performance, conventional synthesis methods for formulating complex geometric graphite shapes are limited due to the intrinsic brittleness and difficulties of high-temperature processing. Here, we report the development of colloidal ink from commercial graphite powders that allows the fabrication of any complex architectures with tunable geometry and directionality via 3D printing at room temperature. The method is enabled via using very small amounts of clay as an additive, allowing the proper design of the graphite-based ink and subsequent binding of graphite platelets during printing. Sheared layers of clay are easily able to flow, adapt, and interface with graphite layers forming strong binding between the layers that make the larger structures. The direct ink writing of complex graphitic architectures without further heat treatments could lead to easy shape engineering and related applications of graphite at various length scales. The printed structures exhibit excellent thermal, electrical, and mechanical properties, and the clay additive does not seem to alter these properties due to the excellent inter-layer dispersion and mixing within the graphite material.

DOI： 10.1016/j.carbon.2021.05.003

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記述言語：英語   出版者・発行元：Journal of Physical Chemistry A  

There has been growing interest in searching for new low-dimensional (low-D) materials for nanoelectronics and energy applications. Most materials have their structural units extended in three dimensions and connected with chemical bonds. When the dimension is reduced, these bonds will be broken, decreasing the stability and making their experimental realization difficult. Here, we show that stable low-D materials can be made from naturally existing planar structural units. This is demonstrated by first-principles study of boron chalcogenides (B-X), which can have various low-D structures with attractive properties. For example, B2O3 can be the thinnest proton-exchange membrane for fuel cells. B-X are wide-gap semiconductors that can complement the narrow-gap 2D metal dichalcogenides for (opto)electronics. Our work sheds light on the stability of low-D materials and suggests guidelines for rational design of new materials.

DOI： 10.1021/acs.jpca.1c02865

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記述言語：英語   出版者・発行元：Journal of Physical Chemistry Letters  

Electronic transport through a metal|semiconductor (M|S) heterojunction is largely determined by its Schottky barrier. In 3D M|S junctions, the barrier height determines the turn-on voltage and is often pinned by the interface states, causing Fermi level pinning (FLP). The pinning strength in 3D depends on the ratio Ci/CM between the interface quantum capacitance Ci and the metal surface capacitance CM. In 2D, the interface dipole does not influence the band alignment, but still affects the Schottky barrier and transport. In light of the general interest in building 2D electronics, in this work we discover the relevant material parameters which dictate the behavior and strength of FLP in 2D M|S contacts. Using a multiscale model combining first-principles, continuum electrostatics, and transport calculations, we study a realistic Gr|MoS2 interface as an example with high interface state density (Ci/CM » 1). Transport calculations show partial pinning with a strength P ~0.6, while a 3D junction with similar heterogeneity gives full pinning with P = 1 as expected. We further show that in 2D M|S contacts the turn-on voltage and pinning strength are affected by a physical parameter l/λD, the ratio between the interface width l, and the thermal de Broglie wavelength λD. Pinning is absent for ideal line-contacts (l/λD = 0), but increases for realistic l/λD values.

DOI： 10.1021/acs.jpclett.0c03663

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記述言語：英語   出版者・発行元：ACS Nano  

Graphene is a promising material for many biointerface applications in engineering, medical, and life-science domains. Here, we explore the protection ability of graphene atomic layers to metals exposed to aggressive sulfate-reducing bacteria implicated in corrosion. Although the graphene layers on copper (Cu) surfaces did not prevent the bacterial attachment and biofilm growth, they effectively restricted the biogenic sulfide attack. Interestingly, single-layered graphene (SLG) worsened the biogenic sulfide attack by 5-fold compared to bare Cu. In contrast, multilayered graphene (MLG) on Cu restricted the attack by 10-fold and 1.4-fold compared to SLG-Cu and bare Cu, respectively. We combined experimental and computational studies to discern the anomalous behavior of SLG-Cu compared to MLG-Cu. We also report that MLG on Ni offers superior protection ability compared to SLG. Finally, we demonstrate the effect of defects, including double vacancy defects and grain boundaries on the protection ability of atomic graphene layers.

DOI： 10.1021/acsnano.0c03987

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記述言語：英語   出版者・発行元：ACS Nano  

Corrosion by sulfur compounds is a long-standing challenge in many engineering applications. Specifically, designing a coating that protects metals from both abiotic and biotic forms of sulfur corrosion remains an elusive goal. Here we report that atomically thin layers (∼4) of hexagonal boron nitride (hBN) act as a protective coating to inhibit corrosion of the underlying copper (Cu) surfaces (∼6-7-fold lower corrosion than bare Cu) in abiotic (sulfuric acid and sodium sulfide) and biotic (sulfate-reducing bacteria medium) environments. The corrosion resistance of hBN is attributed to its outstanding barrier properties to the corrosive species in diverse environments of sulfur compounds. Increasing the number of atomic layers did not necessarily improve the corrosion protection mechanisms. Instead, multilayers of hBN were found to upregulate the adhesion genes in Desulfovibrio alaskensis G20 cells, promote cell adhesion and biofilm growth, and lower the protection against biogenic sulfide attack when compared to the few layers of hBN. Our findings confirm hBN as the thinnest coating to resist diverse forms of sulfur corrosion.

DOI： 10.1021/acsnano.0c03625

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記述言語：英語   出版者・発行元：Nature Communications  

Excitonic condensate has been long-sought within bulk indirect-gap semiconductors, quantum wells, and 2D material layers, all tried as carrying media. Here, we propose intrinsically stable 2D semiconductor heterostructures with doubly-indirect overlapping bands as optimal platforms for excitonic condensation. After screening hundreds of 2D materials, we identify candidates where spontaneous excitonic condensation mediated by purely electronic interaction should occur, and hetero-pairs Sb2Te2Se/BiTeCl, Hf2N2I2/Zr2N2Cl2, and LiAlTe2/BiTeI emerge promising. Unlike monolayers, where excitonic condensation is hampered by Peierls instability, or other bilayers, where doping by applied voltage is required, rendering them essentially non-equilibrium systems, the chemically-specific heterostructures predicted here are lattice-matched, show no detrimental electronic instability, and display broken type-III gap, thus offering optimal carrier density without any gate voltages, in true-equilibrium. Predicted materials can be used to access different parts of electron-hole phase diagram, including BEC-BCS crossover, enabling tantalizing applications in superfluid transport, Josephson-like tunneling, and dissipationless charge counterflow.

DOI： 10.1038/s41467-020-16737-0

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記述言語：英語   出版者・発行元：Nano Letters  

The effect of flexoelectric voltage on the electronic and optical properties of single- and double-wall carbon nanotubes is evaluated by the first-principles calculations. The voltage between the inner channel of curved sp2 carbon nanostructures and their surroundings scales linearly with nanotube wall curvature and can be boosted/reversed by appropriate outer wall functionalization. We predict and verify computationally that in double-wall nanotubes, flexoelectricity causes a straddling to staggered band gap transition. Accurate band structure calculations taking into account quasiparticle corrections and excitonic effects lead to an estimated critical diameter of ∼24 Å for this transition. Double-wall nanotubes above this diameter have staggered band alignment and could be potentially used for charge separation in photovoltaic devices.

DOI： 10.1021/acs.nanolett.9b05345

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出版者・発行元：npj 2D Materials and Applications  

Encapsulation by hexagonal boron nitride (hBN) has been widely used to address intrinsic properties of two-dimensional (2D) materials. The hBN encapsulation, however, can alter properties of 2D materials through interlayer orbital hybridization. In this paper, we present measurements of temperature dependence of photoluminescence intensity from monolayer MoS2 encapsulated by hBN flakes. The obtained temperature dependence shows an opposite trend to that of previously observed in a monolayer MoS2 on a SiO2 substrate. This is caused by the existence of stable momentum-forbidden dark excitons in the hBN-encapsulated MoS2. Ab-initio band-structure calculations have shown that orbital hybridization between MoS2 and hBN leads to upward shift of Γ-valley of MoS2, which results in lowering of energy of the momentum-forbidden dark excitons. This work shows an important implication that the hBN-encapsulated structures used to address intrinsic properties of two-dimensional crystals can alter basic properties of encapsulated materials.

DOI： 10.1038/s41699-019-0108-4

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記述言語：英語   出版者・発行元：ACS Nano  

Despite being only a few atoms thick, single-layer two-dimensional (2D) materials display strong electron-photon interactions that could be utilized in efficient light modulators on extreme subwavelength scales. In various applications involving light modulation and manipulation, materials with strong optical response at different wavelengths are required. Using qualitative analytical modeling and first-principles calculations, we determine the theoretical limit of the maximum optical response such as absorbance (A) and reflectance (R) in 2D materials and also conduct a computational survey to seek out those with best A and R in various frequency ranges, from mid-infrared to deep-ultraviolet. We find that 2D boron has broadband reflectance R > 99% for >100 layers, surpassing conventional thin films of bulk metals such as silver. Moreover, we identify 2D monolayer semiconductors with maximum response, for which we obtain quantitative estimates by calculating quasiparticle energies and accounting for excitonic effects by solving the Bethe-Salpeter equation. We found several monolayer semiconductors with absorbances -30% in different optical ranges, which are more than half of the maximum possible value, Alim = 1/2, for a freestanding 2D material. Our study predicts 2D materials which can potentially be used in ultrathin reflectors and absorbers for optoelectronic application in various frequency ranges.

DOI： 10.1021/acsnano.8b03754

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記述言語：英語   出版者・発行元：Advanced Materials  

Composition and phase specific 2D transition metal dichalogenides (2D TMDs) with a controlled electronic and chemical structure are essential for future electronics. While alloying allows bandgap tunability, heterostructure formation creates atomically sharp electronic junctions. Herein, the formation of lateral heterostructures from quaternary 2D TMD alloys, by thermal annealing, is demonstrated. Phase separation is observed through photoluminescence and Raman spectroscopy, and the sharp interface of the lateral heterostructure is examined via scanning transmission electron microscopy. The composition-dependent transformation is caused by existence of miscibility gap in the quaternary alloys. The phase diagram displaying the miscibility gap is obtained from the reciprocal solution model based on density functional theory and verified experimentally. The experiments show direct evidence of composition-driven heterostructure formation in 2D atomic layer systems.

DOI： 10.1002/adma.201804218

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記述言語：英語   出版者・発行元：Journal of Physical Chemistry Letters  

Two-dimensional single-layer boron (borophene) has emerged as a new material with several intriguing properties. Recently, the β12 polymorph of borophene was grown on Ag(111), and observed to host Dirac fermions. Similar to graphene, β12 borophene can be described as atom-vacancy pseudoalloy on a closed-packed triangular lattice; however, unlike graphene, the origin of its Dirac fermions is yet unclear. Here, using first-principles calculations, we probe the origin of Dirac fermions in freestanding and Ag(111)-supported β12 borophene. The freestanding β12 sheet hosts two Dirac cones and a topologically nontrivial Dirac nodal line with interesting Dirac-like edge states. On Ag(111), the Dirac cones develop a gap, whereas the topologically protected nodal line remains intact, and its position in the Brillouin zone matches that of the Dirac-like electronic states seen in the experiment. The presence of nontrivial topological states near the Fermi level in borophene makes its electronic properties important for both fundamental and applied research.

DOI： 10.1021/acs.jpclett.8b00640

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記述言語：英語   出版者・発行元：ACS Nano  

A van der Waals (vdW) heterostructure composed of multivalley systems can show excitonic optical responses from interlayer excitons that originate from several valleys in the electronic structure. In this work, we studied photoluminescence (PL) from a vdW heterostructure, WS2/MoS2, deposited on hexagonal boron nitride (hBN) flakes. PL spectra from the fabricated heterostructures observed at room temperature show PL peaks at 1.3-1.7 eV, which are absent in the PL spectra of WS2 or MoS2 monolayers alone. The low-energy PL peaks we observed can be decomposed into three distinct peaks. Through detailed PL measurements and theoretical analysis, including PL imaging, time-resolved PL measurements, and calculation of dielectric function ϵ(ω) by solving the Bethe-Salpeter equation with G0W0, we concluded that the three PL peaks originate from direct K-K interlayer excitons, indirect Q-Γ interlayer excitons, and indirect K-Γ interlayer excitons.

DOI： 10.1021/acsnano.7b08253

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記述言語：英語   出版者・発行元：Advanced Materials  

Alloying/doping in 2D material is important due to wide range bandgap tunability. Increasing the number of components would increase the degree of freedom which can provide more flexibility in tuning the bandgap and also reduces the growth temperature. Here, synthesis of quaternary alloys MoxW1−xS2ySe2(1−y) is reported using chemical vapor deposition. The composition of alloys is tuned by changing the growth temperatures. As a result, the bandgap can be tuned which varies from 1.61 to 1.85 eV. The detailed theoretical calculation supports the experimental observation and shows a possibility of wide tunability of bandgap.

DOI： 10.1002/adma.201702457

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出版者・発行元：Chemistry of Materials  

Transition metal dichalcogenide (TMD) alloys form a broad class of two-dimensional (2D) layered materials with tunable bandgaps leading to interesting optoelectronic applications. In the bottom-up approach of building these atomically thin materials, atomic doping plays a crucial role. Here we demonstrate a single step CVD (chemical vapor deposition) growth procedure for obtaining binary alloys and heterostructures by tuning atomic composition. We show that a minute doping of tin during the growth phase of the Mo1-xWxS2 alloy system leads to formation of lateral and vertical heterostructure growth. High angle annular dark field scanning transmission electron microscopy (HAADF-STEM) imaging and density functional theory (DFT) calculations also support the modified stacking and growth mechanism due to the nonisomorphous Sn substitution. Our experiments demonstrate the possibility of growing heterostructures of TMD alloys whose spectral responses can be desirably tuned for various optoelectronic applications.

DOI： 10.1021/acs.chemmater.7b02407

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出版者・発行元：Journal of Materials Chemistry C  

Two-dimensional (2D) superconductors have attracted great attention in recent years due to the possibility of new phenomena in lower dimensions. With many bulk transition metal carbides being well-known conventional superconductors, here we perform first-principles calculations to evaluate the possible superconductivity in a 2D monolayer Mo2C. Three candidate structures (monolayer alpha-Mo2C, 1T MXene-Mo2C, and 2H MXene-Mo2C) are considered and the most stable form is found to be 2H MXene-Mo2C. Electronic structure calculations indicate that both unpassivated and passivated 2H forms exhibit metallic properties. We obtain phonon frequencies and electron-phonon couplings using density-functional perturbation theory, and based on the BCS theory and the McMillan equation, estimate the critical temperatures to be in the ∼0-13 K range, depending on the species of surface termination (O, H and OH). The optimal termination group is H, which can increase the electron-phonon coupling and bring the critical temperature to 13 K. This shows a rather high critical temperature, tunable by surface termination, making this 2D carbide an interesting test bed for low-dimensional superconductivity.

DOI： 10.1039/c7tc00789b

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出版者・発行元：Carbon  

Recently synthesized graphitic honeycomb structures, consisting of sp2-bonded graphene nanoribbons connected by sp3-bonded “hinges” are investigated theoretically. Honeycombs of different “wall-chiralities” (armchair and zigzag) and sizes are studied. Simulation of the reconstruction of the hinges shows that zigzag honeycombs spontaneously rearrange, resulting in a new structure. Elastic mechanical simulations show that the Young's modulus of the structures is determined solely by the density of the hinges, regardless of the structural orientation or regularity. Compression tests display a distinct behavior of self-localized deformation, similar to that of macroscopic honeycombs. Interestingly, the failure strain of the honeycomb structure is affected significantly by its lattice size and geometrical regularity. Electronic band structures of different types of honeycombs are calculated, showing that the conductivity of armchair honeycombs follows the well-known “3n”-dependency, while zigzag honeycombs are always metallic.

DOI： 10.1016/j.carbon.2016.11.020

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出版者・発行元：Journal of Physical Chemistry C  

Pillared 3D carbon architectures, with the graphene layers and carbon nanotubes connected by topological junctions, have been produced and observed, as reported recently. However, the atomistic details of such junctions are hard to discern in microscopy and remain presently unclear. The simplest junction contains six heptagons in the transition region between the nanotube and graphene. Although these junctions make the pillared architectures possible, they are susceptible to failure when the whole structure undergoes mechanical or thermal stress. In this work we consider "nanochimneys", a variety of special junctions with cones in between the nanotube and graphene parts. We explore the structures of the nanochimneys (NCs) and determine their underlying topological requirements. We also study the thermal conductance of these pillared architectures and show that NCs conduct heat better than regular simple junctions. (Figure Presented).

DOI： 10.1021/acs.jpcc.6b11350

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記述言語：英語   出版者・発行元：Nano Letters  

With the lateral coplanar heterojunctions of two-dimensional monolayer materials turning into reality, the quantitative understanding of their electronic, electrostatic, doping, and scaling properties becomes imperative. In contrast to traditional bulk 3D junctions where carrier equilibrium is reached through local charge redistribution, a highly nonlocalized charge transfer (trailing off as 1/x away from the interface) is present in lateral 2D junctions, increasing the junction size considerably. The depletion width scales as p-1, while the differential capacitance varies very little with the doping level p. The properties of lateral 2D junctions are further quantified through numerical analysis of realistic materials, with graphene, MoS2, and their hybrid serving as examples. Careful analysis of the built-in potential profile shows strong reduction of Fermi level pinning, suggesting better control of the barrier in 2D metal-semiconductor junctions.

DOI： 10.1021/acs.nanolett.6b01822

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出版者・発行元：Journal of Physical Chemistry C  

Fluorination has been instrumental for tuning the properties of several two-dimensional (2D) materials, including graphene, h-BN, and MoS2. However, its potential application has not yet been explored in 2D silicon carbide (SiC), a promising material for nanoelectronic devices. We investigate the structural, electronic, and magnetic properties of fully and partially fluorinated 2D SiC sheets and nanoribbons by means of density functional theory combined with cluster expansion calculations. We find that fully fluorinated 2D SiC exhibits chair configurations and a nonmagnetic semiconducting behavior. Fluorination is shown to be an efficient approach for tuning the band gap. Four ground states of partially fluorinated SiC, SiCF2x with x = 0.0625, 0.25, 0.5, 0.75, are obtained by cluster expansion calculations. All of them exhibit nanoroad patterns, with the x = 0.5 structure identified as the most stable one. The x = 0.0625 structure is a nonmagnetic metal, while the other three are all ferromagnetic half-metals, whose properties are not affected by the edge states. We propose an effective approach for modulating the electronic and magnetic behavior of 2D SiC, paving the way to applications of SiC nanostructures in integrated multifunctional and spintronic nanodevices.

DOI： 10.1021/acs.jpcc.6b01706

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記述言語：英語   出版者・発行元：Nano Letters  

Two-dimensional boron is expected to exhibit various structural polymorphs, all being metallic. Additionally, its small atomic mass suggests strong electron-phonon coupling, which in turn can enable superconducting behavior. Here we perform first-principles analysis of electronic structure, phonon spectra, and electron-phonon coupling of selected 2D boron polymorphs and show that the most stable structures predicted to feasibly form on a metal substrate should also exhibit intrinsic phonon-mediated superconductivity, with estimated critical temperature in the range of Tc ≈ 10-20 K.

DOI： 10.1021/acs.nanolett.6b00070

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出版者・発行元：Advanced Materials Interfaces  

Buckling nanopatterns of monoatomic layer 2D materials on metal substrates attract significant attention due to their rich interface morphology affecting electronic applications. An experimental-theoretical study of a 2D boron-nitrogen-carbon (B x/2N x/2C1-x) alloy on a Ru(0001) surface is conducted and a profound relation between the composition x and the degree of buckling is discovered. Experimentally, real carbon-boron-nitrogen alloys on the Ru(0001) surface are demonstrated and various morphologies of pure and mixed compounds are shown. Density functional theory calculations are further carried out using the supercells of graphene, hexagonal boron nitride (h-BN), and random BNC on Ru(0001), as well as Monte Carlo simulations for elucidating the kinetics of their growth. The results show that unlike pure compounds (h-BN or C), the carbon-boron-nitrogen mix on Ru(0001) mostly exists in an uncorrugated form, thus greatly improving the interface contact. The likely cause of the diminished corrugation is a softening of bond angular interactions in the alloy relative to the pure phases. A 2 D boron-nitrogen-carbon (BNC) alloy on a Ru(0001) surface is experimentally and theoretically studied, and a profound relation between the composition and the degree of buckling is discovered. BNC on Ru(0001) exists in a mostly uncorrugated form. The likely cause of diminished corrugation is a softening of bond angular interactions in the alloy relative to the pure phases.

DOI： 10.1002/admi.201500322

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記述言語：英語   出版者・発行元：ACS Nano  

Intrinsic semimetallicity of graphene and silicene largely limits their applications in functional devices. Mixing carbon and silicon atoms to form two-dimensional (2D) silicon carbide (SixC1-x) sheets is promising to overcome this issue. Using first-principles calculations combined with the cluster expansion method, we perform a comprehensive study on the thermodynamic stability and electronic properties of 2D SixC1-x monolayers with 0 ≤ x ≤ 1. Upon varying the silicon concentration, the 2D SixC1-x presents two distinct structural phases, a homogeneous phase with well dispersed Si (or C) atoms and an in-plane hybrid phase rich in SiC domains. While the in-plane hybrid structure shows uniform semiconducting properties with widely tunable band gap from 0 to 2.87 eV due to quantum confinement effect imposed by the SiC domains, the homogeneous structures can be semiconducting or remain semimetallic depending on a superlattice vector which dictates whether the sublattice symmetry is topologically broken. Moreover, we reveal a universal rule for describing the electronic properties of the homogeneous SixC1-x structures. These findings suggest that the 2D SixC1-x monolayers may present a new "family" of 2D materials, with a rich variety of properties for applications in electronics and optoelectronics.

DOI： 10.1021/acsnano.5b02753

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記述言語：英語   出版者・発行元：Journal of Physical Chemistry Letters  

Doped, substituted, or alloyed graphene is an attractive candidate for use as a tunable element of future nanomechanical and optoelectronic devices. Here we use the density functional theory, density functional tight binding, cluster expansion, and molecular dynamics to investigate the thermal stability and electronic properties of a binary 2D alloy of graphitic carbon and nitrogen (C<inf>1-x</inf>N<inf>x</inf>). The stability range naturally begins from graphene and must end before x = 1, where pure nitrogen rather forms molecular gas. This poses a compelling question of what highest x < 1 still permits stable 2D hexagonal lattice. Such upper limit on the nitrogen concentration that is achievable in a stable alloy can be found based on the phonon and molecular dynamics calculations. The stability switchover is predicted to between x = 1/3 (33.3%) and x = 3/8 (37.5%), and no stable hexagonal lattice two-dimensional CN alloys can exist at the N concentration of x = 3/8 (37.5%) and higher.

DOI： 10.1021/jz502093c

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記述言語：英語   出版者・発行元：Nanoscale  

Creation of free edges in graphene during mechanical fracture is a process that is important from both fundamental and technological points of view. Here we derive an analytical expression for the energy of a free-standing reconstructed chiral graphene edge, with chiral angle varying from 0° to 30°, and test it by first-principles computations. We then study the thermodynamics and kinetics of fracture and show that during graphene fracture under uniaxial load it is possible to obtain fully reconstructed zigzag edges through sequential reconstructions at the crack tip. The preferable condition for this process is high temperature (T ∼ 1000 K) and low (quasi-static) mechanical load (KI ∼ 5.0 eV A˚-5/2). Edge configurations of graphene nanoribbons may be tuned according to these guidelines.

DOI： 10.1039/c4nr06332e

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出版者・発行元：Nanoscale  

The search for new candidate semiconductors with direct band gaps of ∼1.4 eV has attracted significant attention, especially among the two-dimensional (2D) materials, which have become potential candidates for next-generation optoelectronics. Herein, we systematically studied 2D Bx/2Nx/2C1-x (0 < x < 1) compounds in particular focus on the four stoichiometric Bx/2Nx/2C1-x (x = 2/3, 1/2, 2/5 and 1/3) using a recently developed global optimization method (CALYPSO) in conjunction with density functional theory. Furthermore, we examine more stoichiometries by the cluster expansion technique based on a hexagonal lattice. The results reveal that all monolayer Bx/2Nx/2C1-x stoichiometries adopt a planar honeycomb character and are dynamically stable. Remarkably, electronic structural calculations show that most of Bx/2Nx/2C1-x phases possess direct band gaps within the optical range, thereby they can potentially be used in high-efficiency conversion of solar energy to electric power, as well as in p-n junction photovoltaic modules. The present results also show that the band gaps of Bx/2Nx/2C1-x can be widely tuned within the optical range by changing the concentration of carbon, thus allowing the fast development of band gap engineered materials in optoelectronics. These new findings may enable new approaches to the design of microelectronic devices.

DOI： 10.1039/c5nr03344f

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記述言語：英語   出版者・発行元：Nanoscale  

The applied uniaxial stress can break the original symmetry of a material, providing an experimentally feasible way to alter material properties. Here, we explore the effects of uniaxial stress along an arbitrary direction on mechanical and electronic properties of phosphorene, showing the enhancement of inherent anisotropy. Basic physical quantities including Young's modulus, Poisson's ratio, band gap, and effective carrier masses under external stress are all computed from first principles using density functional theory, while the final results are presented in compact analytical forms.

DOI： 10.1039/c5nr00355e

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PubMed

出版者・発行元：Annalen der Physik  

Monolayer transition metal dichalcogenides are promising materials for photoelectronic devices. Among them, molybdenum disulphide (MoS2) and tungsten disulphide (WS2) are some of the best candidates due to their favorable band gap values and band edge alignments. Here, various perturbative corrections to the DFT electronic structure, e.g. GW, spin-orbit coupling, as well as many-body excitonic and trionic effects are considered, and accurate band gaps as a function of homogeneous biaxial strain in these materials are calculated. All of these corrections are shown to be of comparable magnitudes and need to be included in order to obtain an accurate electronic structure. The strain at which the direct-to-indirect gap transition occurs is calculated. After considering all contributions, the direct to indirect gap transition strain is predicted to be at 2.7% in MoS2 and 3.9% in WS2. These values are generally higher than the previously reported theoretical values.

DOI： 10.1002/andp.201400098

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記述言語：英語   出版者・発行元：Nanoscale  

Binary alloys present a promising venue for band gap engineering and tuning of other mechanical and electronic properties of materials. Here we use the density-functional theory and cluster expansion to investigate the thermodynamic stability and electronic properties of 2D transition metal dichalcogenide (TMD) binary alloys. We find that mixing electron-accepting or electron-donating transition metals with 2D TMD semiconductors leads to degenerate p- or n-doping, respectively, effectively rendering them metallic. We then proceed to investigate the electronic properties of semiconductor-semiconductor alloys. The exploration of the configurational space of the 2D molybdenum-tungsten disulfide (Mo1-xWxS2) alloy beyond the mean field approximation yields insights into anisotropy of the electron and hole effective masses in this material. The effective hole mass in the 2D Mo 1-xWxS2 is nearly isotropic and is predicted to change almost linearly with the tungsten concentration x. In contrast, the effective electron mass shows significant spatial anisotropy. The values of the band gap in 2D Mo1-xWxS2 and MoSe 2(1-x)S2x are found to be configuration-dependent, exposing the limitations of the mean field approach to band gap analysis in alloys. © 2014 the Partner Organisations.

DOI： 10.1039/c4nr00177j

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PubMed

記述言語：英語   出版者・発行元：Journal of Physical Chemistry Letters  

We study the Li clustering process on graphene and obtain the geometry, nucleation barrier, and electronic structure of the clusters using first-principles calculations. We estimate the concentration-dependent nucleation barrier for Li on graphene. While the nucleation occurs more readily with increasing Li concentration, possibly leading to the dendrite formation and failure of the Li-ion battery, the existence of the barrier delays nucleation and may allow Li storage on graphene. Our electronic structure and charge transfer analyses reveal how the fully ionized Li adatoms transform to metallic Li during the cluster growth on graphene. © 2014 American Chemical Society.

DOI： 10.1021/jz500199d

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出版者・発行元：Physical Review B - Condensed Matter and Materials Physics  

We explore theoretically the possibility of growing GaN films in a nonpolar orientation on planar high-index Si(hhk) substrates. Candidate substrates were identified by requiring that they are well lattice matched, on a length scale of several unit cells, to GaN in the nonpolar m-plane orientation. These candidate orientations were then used to construct atomistic models of the GaN/Si(hhk) interface. Using density functional theory, we then computed the formation energies of these nonpolar interfaces and compared them to those of competing polar interfaces. We find that Si(112) and Si(113) offer potentially favorable substrates for the growth of nonpolar m-plane GaN.

DOI： 10.1103/PhysRevB.87.045314

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出版者・発行元：ACS National Meeting Book of Abstracts  

Type-II core-shell quantum dots provide unique control over spatial distribution of carriers. The band offset value of the comprising materials establishes the direction of the energy transfer and enables optical transition energies beyond band gap restricions: The type-II quantum dots can emit at lower energies than the band gaps of comprising materials. The artificial solar energy harvesting technology involves photoinduced Interface charge separation on the interfaces of different materials: a photoabsorber (X), an electron conductor (E), and a hole conductor (H). The energies of valence band maximum, conduction band minimum, and band-gap for these materials must satisfy certain conditions that provide a frequency-selective electron-hole-pair creation in X, and an efficient charge transport of en electron from X to E and a hole from X to H materials respectively. We study interfaces of a wide range of photovoltaic materials with various ionization energies, electron affinities, Fermi energies, crystalline structure. Specifically, we focus on photoexcited electron transfer in interfaces of II-VI group semiconductors of wurtzite crystal symmetry in form of thin film interfaces and quantum dots. An interface of CdS/ZnSe materials has a potential for the primary event of charge separation represented by the following reaction (CdS)(ZnSe) + hw -> (CdS)*(ZnSe) -> (CdS)-(ZnSe)+, where symbols *, -, + stand for excited, negatively, and positively charged states of a material, respectively. Theoretical calculations based on density matrix method provide charge transfer dynamics, photocurrent, photovoltage, and open circuit I-V curve for ground and photoexcited state.

Scopus

出版者・発行元：Physical Review B - Condensed Matter and Materials Physics  

Recent experiments have shown a dramatic increase in the conductivity of PbSe nanocrystalline films after hydrazine treatment, suggesting that hydrazine may create free carriers in PbSe nanocrystals. Here, we study the effect of hydrazine adsorption on the electronic structure of PbSe nanocrystals using density functional theory. The physisorption of the intact hydrazine molecule and its dissociative chemisorption on different surfaces of PbSe are considered. Despite experimental indications of the n-type doping by hydrazine in PbSe, no theoretical evidence of the effect is found. Instead, PbSe is predicted to remain an intrinsic semiconductor after surface doping by hydrazine, and become a p-type semiconductor after doping by the hydrazine fragments. We attribute the discrepancy between experiment and theory to indirect effects, such as self-doping by excess surface atoms due to selective surface etching. © 2011 American Physical Society.

DOI： 10.1103/PhysRevB.83.235419

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出版者・発行元：Journal of Physical Chemistry C  

Using ab initio plane wave pseudopotential calculations, we study the energetics and structure of adsorbed linear arrays of oxygen and aziridine on carbon nanotubes, graphitic ribbons, and graphene sheets. Chemisorption of arrays of O or NH causes splitting of the CC bond and local deformation of the graphitic structures. The (3, 3) nanotube cross section assumes a teardrop-like shape, while graphene sheets warp into a new local geometry around the chemisorbed molecules. The interior of a (3, 3) nanotube is less prone to oxidation than the exterior because of steric effects. A zigzag (6, 0) nanotube is less reactive and thus chemically more stable than an armchair (3, 3) nanotube. The results suggest a partial explanation for the experimentally observed selective etching of metallic carbon nanotubes. © 2009 American Chemical Society.

DOI： 10.1021/jp904555n

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出版者・発行元：Journal of the American Chemical Society  

Most gas-surface chemical reactions occur via reaction of adsorbed species to form a thermal-energy (∼kT) product; however, some instances exist where an energetic projectile directly reacts with an adsorbate in a single-collision event to form a hyperthermal product (with a kinetic energy of a few eV). Here we show for the first time that 30-300 eV F+ bombardment of fluorinated Ag and Si surfaces produces "ultrafast" F2- products with exit energies of up to 90 eV via a multistep direct-reaction mechanism. Experiments conclusively show that the projectile F atom ends up in the fast molecular product despite the fact that the impact energy is far greater than typical bond energies. © 2009 American Chemical Society.

DOI： 10.1021/ja807672n

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PubMed

記述言語：英語   出版者・発行元：Journal of Chemical Physics  

We present a reactive empirical potential with environment-dependent bond strengths for the carbon-oxygen (CO) system. The distinct feature of the potential is the use of three adjustable parameters characterizing the bond: the strength, length, and force constant, rather than a single bond order parameter, as often employed in these types of potentials. The values of the parameters are calculated by fitting results obtained from density functional theory. The potential is tested in a simulation of oxidative unzipping of graphene sheets and carbon nanotubes. Previous higher-level theoretical predictions of graphene unzipping by adsorbed oxygen atoms are confirmed. Moreover, nanotubes with externally placed oxygen atoms are found to unzip much faster than flat graphene sheets. © 2008 American Institute of Physics.

DOI： 10.1063/1.2940329

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PubMed

出版者・発行元：Physical Review B - Condensed Matter and Materials Physics  

Optimized model potentials for mercury-mercury and mercury-carbon interactions are used in molecular dynamics simulations to study wetting and solidification of liquid mercury encapsulated in single-walled carbon nanotubes. The contact angle of mercury in the nanotube cavity increases linearly with wall curvature. The solid-liquid transition becomes less well defined as nanotube diameter decreases, while the melting temperature drops exponentially. A concentric cylindrical-shell structure is predicted for solidified mercury in small (20,20) nanotubes, while a polycrystalline structure appears in larger (40,40) nanotubes. © 2007 The American Physical Society.

DOI： 10.1103/PhysRevB.76.195444

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記述言語：英語   出版者・発行元：Physical Review Letters  

Pure bending of single-walled carbon nanotubes between (5,5) and (50,50) is studied using molecular dynamics based on the reactive bond order potential. Unlike smaller nanotubes, bending of (15,15) and larger ones exhibits an intermediate deformation in the transition between the buckled and fully kinked configurations. This transient bending regime is characterized by a gradual and controllable flattening of the nanotube cross section at the buckling site. Unbending of a kinked nanotube bypasses the transient bending regime, exhibiting a hysteresis due to van der Waals attraction between the tube walls at the kinked site. © 2006 The American Physical Society.

DOI： 10.1103/PhysRevLett.97.245501

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記述言語：英語   出版者・発行元：Nano Letters  

Imaging of surfaces with carbon nanotube probes in tapping mode results frequently in complex behavior in the amplitude-distance curves monitored. Using molecular mechanics simulations, we calculate the force exerted on a nanotube pressed against a smooth surface as it undergoes deformation and buckling. This nonlinear force is then used in a macroscopic equation, describing the response of a damped harmonic oscillator, to predict the amplitude response of a nanotube AFM probe. Similarities between the prediction and experiment suggest that the complex amplitude response seen in the experiment may be explained by the nonlinearity in the force exerted on the nanotube and thus must not necessarily be related to the structure of the surface. © 2006 American Chemical Society.

DOI： 10.1021/nl060831o

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PubMed

出版者・発行元：Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms  

Relative ion yields of low energy (320 eV) Ne+ ions scattered off a number of elemental surfaces are compared. Ion survival probabilities are seen to change significantly from one element to another depending on the surface work function, suggesting that resonant charge exchange between the metal conduction band and Ne 3s atomic level may be just as important as Auger neutralization processes. The observed yield dependence on work function is qualitatively explained using a description of resonant neutralization (RN) based on the Anderson model of an atomic level near a surface. Auger processes are found to be important in determining the final charge state of outgoing ions, while quasi-resonant interactions between the core atomic levels are seen to be nonexistent. © 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.nimb.2006.03.187

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記述言語：英語   出版者・発行元：Nano Letters  

Electrowetting of carbon nanotubes by mercury was studied using classical molecular dynamics simulations in conjunction with a macroscopic electrocapillarity model. A scaled ab initio mercury dimer potential, optimized to reproduce the mercury liquid density (at 300 K), melting point, and wetting angle on graphite, was selected for the simulations. Wetting of (20,20) single-walled carbon nanotubes by mercury occurs above a threshold voltage of 2.5 V applied across the interface. Both the electrocapillary pressure and imbibition velocity increase quadratically with voltage and can acquire large values, for example, 2.4 kbar and 28 m/s at 4 V, indicating a notable driving force. The observed voltage scaling can be captured by the Lucas-Washburn equation modified to include a wetting-line friction term. © 2006 American Chemical Society.

DOI： 10.1021/nl052393b

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記述言語：英語   出版者・発行元：Science  

We demonstrate reversible wetting and filling of open single-wall carbon nanotubes with mercury by means of electrocapillary pressure originating from the application of a potential across an individual nanotube in contact with a mercury drop. Wetting improves the conductance in both metallic and semiconducting nanotube probes by decreasing contact resistance and forming a mercury nanowire inside the nanotube. Molecular dynamics simulations corroborate the electrocapillarity-driven filling process and provide estimates for the imbibition speed and electrocapillary pressure.

DOI： 10.1126/science.1120385

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PubMed

出版者・発行元：Applied Surface Science  

X-ray photo-electron spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS) along with MARLOWE and TRIM computer simulations were used to study the retention of Cs + primary ions in Si substrates during sputtering. Cs concentrations were found to depend on (a) primary ion energy, (b) primary ion incidence angle, and (c) sputtering time (within the transient region). With the exception of the XPS and RBS data collected as a function of Cs + impact energy, Cs concentration variations, Δ[Cs], appear to correlate with sputter yield variations, ΔSY, via Δ[Cs] ∝ 1/(ΔSY+1). Computer simulations reveal variations in Cs + scattering with impact energy, etc. This and/or self sputtering may explain the inconsistencies noted with impact energy. © 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2004.03.043

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出版者・発行元：Vacuum  

The kinetics of atomic hydrogen isothermal adsorption and desorption on a Si(1 0 0) surface was studied using the time-of-flight scattering and recoiling spectrometry technique at temperatures below and above the thermal desorption threshold. A continuous decrease in saturation coverage with temperature under constant atomic hydrogen exposure has been observed in both regions for temperatures in the range 325-820 K. For TS = 500-650 K, the decrease is described by a kinetic model where Eley-Rideal (ER) abstraction is responsible for hydrogen removal from the surface and hydrogen coverage depends on the temperature due to the changing rate of migration from precursor to primary monohydride sites. For TS = 650 K and higher, in addition to the ER abstraction, the thermal desorption from primary monohydride sites leads to a further decrease of the saturation coverage. The first-order desorption rates after source shut-off have been measured and an activation barrier of 1. 89 eV has been obtained. © 2003 Published by Elsevier Ltd.

DOI： 10.1016/j.vacuum.2003.12.027

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記述言語：英語   出版者・発行元：公益社団法人 日本表面真空学会  

The technique of angle resolved mapping of scattering and recoiling imaging spectra (SARIS) combined with computer simulations is demonstrated to be a valuable tool for characterization of atomic collision events on surfaces. The energy distributions of scattered Kr and Ne and fast recoiled Pt and Ni atoms from Pt(111) and Ni(111) surfaces were measured as a function of exit angle. The use of a large area microchannel plate (MCP) detector and time-of-flight (TOF) techniques decreases the collection time and increases the number of detected trajectories above that of other designs. Classical ion trajectory simulations using the three-dimensional scattering and recoiling imaging code (SARIC) are used to simulate the kinematics of the scattering and recoiling particles. It is shown that SARIS mapping allows one to probe the kinematics of both scattered and recoiled particles, the probability for their occurrence in specific trajectories, and the atomic layers from which the particles originate. [DOI: 10.1380/ejssnt.2004.93]

DOI： 10.1380/ejssnt.2004.93

CiNii Research

出版者・発行元：Journal of Chemical Physics  

TOF-SARS measurements of isothermal H adsorption on Si(100) for a continuous range of temperatures Ts=325-750 K were performed. The saturation coverage was found to monotonically decrease with temperature from ∼1.5 to 1 ML. A kinetic model describing competing processes of adsorption, abstraction, and migration between two types of adsorption sites was developed to explain the observed dependencies in the range 500-650 K.

DOI： 10.1063/1.1624827

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出版者・発行元：Surface Science  

The technique of angle resolved mapping of scattering and recoiling imaging spectra (SARIS) combined with computer simulations is demonstrated to be a valuable tool for characterization of atomic collision events on surfaces. The energy distributions of scattered Kr and fast recoiled Pt atoms from a Pt(1 1 1) surface were measured as a function of exit angle. The use of a large area microchannel plate detector and time-of-flight techniques decreases the collection time and increases the number of detected trajectories above that of other designs. Classical ion trajectory simulations using the three-dimensional scattering and recoiling imaging code are used to simulate the kinematics of the scattering and recoiling particles. It is shown that SARIS mapping allows one to probe the kinematics of both scattered and recoiled particles, the probability for their occurrence in specific trajectories, their detection probabilities, and their threshold detection velocity. The measured and simulated energy distributions agree quantitatively if the detection efficiency is taken into account. The observed value of the threshold detection velocity for Pt atoms, νth = 3.78(5) × 104 m/s, is in good agreement with previous studies. © 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0039-6028(03)00840-9

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出版者・発行元：Surface Science  

Calculations of blocking cone sizes for the "blocking geometry" of the scattering and recoiling imaging spectrometry (SARIS) technique have been performed. By fitting calculated points in the space of the parameters of the interacting atomic species, a universal formula for calculating the blocking cone size for arbitrary energies and interacting species has been derived. This provides a "blocking cross-section" and an estimate of the total scattering cross-section of the process under consideration. The results obtained from the formula are compared with experimental SARIS blocking cone data for He+ and Ne+ scattering from a Pt(1 1 1) surface in the energy range 3-20 keV. The blocking cones in this low-energy range are appreciably asymmetric with respect to the interatomic axis. At small interatomic distances and low-projectile energies, the difference in angular size of the upper and lower halves of the blocking cone can be as large as 15%. The results of scattering and recoiling imaging code simulations and molecular dynamics blocking cone trajectory simulations using the Ziegler-Biersack-Littmark potential are in good agreement with experimental blocking cone sizes. Comparison is also made to the results of other formulas for the critical blocking angle found in the literature. © 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0039-6028(01)01511-4

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出版者・発行元：Surface Science  

The kinetics of O2 chemisorption at low dose on Ni(1 1 1) and the nature of the chemisorption site have been studied at 300 and 500 K using time-of-flight scattering and recoiling spectrometry (TOF-SARS), low energy electron diffraction, and scattering and recoiling imaging code (SARIC) simulations. Variations in the TOF-SARS spectra with different crystal alignments during O2 dosing provide direct information on the location of oxygen adatoms on the Ni(1 1 1) surface at very low coverages as well as site-specific occupation rates (Sfcc and Shcp) and occupancies (θfcc and θhcp). A system of equations has been developed that relate the slopes of the scattering and recoiling intensities versus O2 exposure dose to these probabilities and occupancies. The results identify three chemisorption stages as a function of oxygen exposure, each with its own specific occupation rates and occupancies. The first-stage is observed up to θ1 = θfcc approximately 0.21 ML with θhcp = 0, constant S = Sfcc approximately 0.18±0.01, and coverage ratio w = θhcp/θfcc approximately 0 for both 300 and 500 K. The second-stage is observed at coverages between θ1 approximately 0.21 and θ2 approximately 0.32 ML with constant Sfcc = -(0.05±0.01) and Shcp = (0.16±0.02) at 300 K and Sfcc = (0.005±0.003) and Shcp = (0.007±0.003) at 500 K, and coverage ratios w = θhcp/θfcc approximately 1 at 300 K and w = θhcp/θfcc approximately 0.10 at 500 K. The third-stage, observed for θ>0.32 ML, involves saturation coverage of the adsorption sites. SARIC simulations were used to interpret the spectra and the influence of oxygen chemisorption and vibrational effects. A method for determining the `effective Debye temperature Θ*D' that uses the experimental TOF-SARS intensity variations as a function of temperature and the simulated SARIC signals as a function of the mean square vibrational amplitude 〈u2〉 has been developed. The result for this system is Θ*D = 314±10 K.

DOI： 10.1016/S0039-6028(00)00938-9

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出版者・発行元：Journal of Chemical Physics  

The recently developed technique of scattering and recoiling imaging spectrometry (SARIS) is used to probe the effect of hydrogen atoms on the trajectories of 5 keV Ne+ scattering from a Pt(111) surface. Classical kinematic calculations and ion trajectory simulations, using the scattering and recoiling imaging code (SARIC), are carried out in order to probe the details of the interaction and the nature of the perturbation. It is demonstrated that adsorbed hydrogen atoms are capable of deflecting these low kilo-electron-volt Ne trajectories scattering from a Pt surface. These perturbations result in spatial shifts and broadenings of the anisotropic features of the SARIS images that are readily detectable. The scattered Ne atoms lose 0-18% of their initial kinetic energy as a result of the perturbation by the H atoms. The physics of the perturbation on the trajectories can be understood from straightforward classical kinematic calculations and SARIC ion trajectory simulations. © 1999 American Institute of Physics.

DOI： 10.1063/1.480468

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