Coulomb expansion of a van der Waals C60 solid film

Scanning tunneling microscopy study revealed a van der Waals C60 solid film with 13% room-temperature lattice expansion on the GaAs(001) 2×4 surface. The mechanism involves fundamental Coulomb interaction due to charge transfer from the GaAs substrate. Theoretical calculation determines the charge transfer to be 1.76 electrons per C60 molecule. Oriented at its (110) crystallographic axis this film also distinguishes itself from those formed on all other semiconductor and metal substrates where only the low-energy (111) hexagonal packing of C60 molecules was developed. It is shown that this is due to the one-dimensional confinement effect of the anisotropic substrate, which may have the prospect of controlling crystal growth.     

Synchrotron radiation photoemission spectrum study on K3C60 film

K₃C₆₀, single crystal film was prepared on the cleaved (111) surface of C₆₀, single crystal. Synchrotron radiation angle-resolved photoemission spectra were measured at normal emission with sample temperature at × 150K. Up to four subpeaks of LUMO-derived band were observed. These sub-peaks exhibit distinct energy dispersions which resemble in general the theoretical ones calculated for K₃C₆₀ at low temperature with the so-called one-dimensional disordered structure. But there is large deviation of experimental sub-band intervals from the theoretical values. This result is meaningful for the studies of the physical properties of alkali-doped C₆₀ solids, e.g. the mechanism for superconductivity.     

Synthesis and characterization of C3N4 crystal (I)

A successful experimental synthesis of pure crystalline β- and α-C₃N₄ films on Si(100) substrate was carried out by bias-assisted hot filament chemical vapor deposition (bias-HFCVD). It is found that a mixed-phase C₃-_I-Si_xN_y buffer layer was formed between the Si substrate and the C-N film. A “lattice match selection” was proposed to study the growth mechanism of C₃N₄ clusters composed of many crystal columns with hexagonal facets. Project supported by the National Natural Science Foundation of China and the Chinese Academy of Sciences.     

Diamond nucleation on surface of C60 thin layers

Diamond nucleation on the surface of C₆₀ thin layers and intermediate layer of Si substrates are studied by scanning electron microscopy (SEM). The cross-section SEM images of diamond films show that diamond grains really nucleate on the surface of C₆₀ thin layers. The SEM images of diamond nucleating sites show the nucleating aggregation of diamond on C₆₀ surfaces. The preferential oriented diamond films are observed. The plasma pretreatment of C₆₀ sublimating layers is a key factor for diamond nucleation.     

Gorenstein Injective and Projective Complexes with Respect to a Semidualizing Module

Let R be a commutative (possibly non-Noetherian) ring (in order to make things less technical) and C a semidualizing R-module. In this article, we introduce and investigate the notion of G _C -injective (G _C -projective) complexes. This extends Enochs and García Rozas's notion of Gorenstein injective (Gorenstein projective) complexes. We then show that a complex X is G _C -injective (G _C -projective) if and only if X ^m is a G _C -injective (G _C -projective) module for each m ∈ ?.     

Annealing behavior of hexagonal phase content in cubic GaN thin films grown on GaAs (001) by MOCVD

The annealing behavior of the hexagonal phase content in cubic GaN (c-GaN) thin Films grown on GaAs (001) by MOCVD is reported. C-GaN thin films are grown on GaAs (001) substrates by metalorganic chemical vapor deposition (MOCVD). High temperature annealing is employed to treat the as-grown c-GaN thin films. The characterization of the c-GaN films is investigated by photoluminescence (PL) and Raman scattering spectroscopy. The change conditions of the hexagonal phase content in the metastable c-GaN are reported. There is a boundary layer existing in the c-GaN/GaAs film. When being annealed at high temperature, the intensity of the T0_B and LO_B phonon modes from the boundary layer weakens while that of the E₂ phonon mode from the hexagonal phase increases. The content change of hexagonal phase has closer relationship with annealing temperature than with annealing time period.     

Synthesis and characterization of C3N4 hard films

C₃N₄ films have been synthesized on both Si and Ft substrates by microwave plasma chemical vapor deposition (MPCVD) method. X-ray spectra were calculated for single phase α-C₃N₄ and β-C₃N₄ respectively. The experimental X-ray spectra of films deposited on both Si and Pt substrates showed all the strong peaks of α-C₃N₄ and β-C₃N₄ so the films are mixtures of α-C₃N₄ and β-C₃N₄. The N/C atomic ratio is in the range of 1.0–2.0. X-ray photoelectron spectroscopy (XPS) analysis indicated that the binding energy of Is and N ls are 286.2 eV and 399.5 eV respectively, corresponding to polarized C-N bond. Fourier transform infrared absorption (FT-IR) and Raman spectra support the existence of C-N covalent bond in the films. Nano-indentation hardness tests showed that the bulk modulus of a film deposited on Pt is up to 349 GPa     

Über den Einfluss der Oberflächeneigenschaften von Halbleitern auf ihre Eiskeimfähigkeit

The factors controlling the ice nucleation efficiency are studied in this paper on suitably chosen model substances, in particular on silicon. It is found that the critical supersaturation for the growth of ice on a (111)-plane of GaAs is 25% at –25°C; this quantity as well as the number of growing ice crystals (cm^–2) were found to be independent of the dislocation density. The critical supersaturation for the growth of ice on the (111)-plane of Si is strongly dependent on the electrical conductivity of the crystals, but independent of the sign of the majority charge carriers. Epitaxial growth is observed on the hexagonal substrate GaSe only, but not on the cubic GaAs and Si.On the basis of the classical nucleation theory the free energy of adsorption of H₂O on GaSe G _ads =0,48 eV and the specific interfacial free energy _SL =23,2 erg · cm^–2 are evaluated. This indicates that the outermost layer of the ice embryo is in a liquid-like state.Water adsorption isotherms were measured gravimetrically down to –20°C and were found to be of type II (BET, [33]). The amount of adsorbed water and the isosteric heat of adsorption at a given relative pressure depend on the doping of the sample.From this it is concluded that low conductivity material had more adsorption sites than high conductivity material, but these fewer sites on the high conductivity samples were more active in collecting water molecules. The larger water clusters are formed on high conductivity samples in agreement with the higher nucleation efficiency observed in mixing cloud chamber experiments.The electrical conductivity and the sign of the thermoelectric effect of a thin silicon on sapphire film have been measured as a function of oxygen and water vapor pressures. It is found that band bending towards ann-type surface occurred during water chemisorption on Si.This indicates that chemisorbed water molecules act as donor surface states. The charge exchanged between adsorbate and adsorbent is larger on high conductivity samples on account of their higher initial surface potential.Chemisorption sites on Si are proportional to the doping concentration and they produce relatively large water clusters. Hence doping results in a higher nucleation efficiency.     

Gorenstein Homological Dimension with Respect to a Semidualizing Module and a Generalization of a Theorem of Bass

Let C be a semidualizing module for a commutative ring R. In this paper, we study the resulting modules of finite G _C -projective dimension in Bass class, showing that they admit G _C -projective precover. Over local ring, we prove that dim _R (M) ≤ 𝒢? _C  ? id _R (M) for any nonzero finitely generated R-module M, which generalizes a result due to Bass.     

Growth morphology and structural characteristic of C70 single crystals

Large size C₇₀ single crystals with the dimension of more than 5 mm are grown from the vapor phase by controlling nucleation. X-ray diffraction and electron diffraction confirm that in the C₇₀ single crystal a phase of the hexagonal close-packed (hcp) structure coexists with a minor face-center-cubic (fcc) phase at room temperature. The morphologies and their formation mechanism of the C₇₀ single crystals are investigated by means of scanning electron micrascopy and optical microscopy. The influence of growth conditions on the morphologies of C₇₀ single crystals is discussed. Project supported by the National Natural Science Foundation of China (Grant No. 59772026).     

When Some Complement of a Submodule Is a Summand

A module M is said to satisfy the C ₁₁ condition if every submodule of M has a (i.e., at least one) complement which is a direct summand. It is known that the C ₁ condition implies the C ₁₁ condition and that the class of C ₁₁-modules is closed under direct sums but not under direct summands. We show that if M = M ₁ ⊕ M ₂, where M has C ₁₁ and M ₁ is a fully invariant submodule of M, then both M ₁ and M ₂ are C ₁₁-modules. Moreover, the C ₁₁ condition is shown to be closed under formation of the ring of column finite matrices of size Γ, the ring of m-by-m upper triangular matrices and right essential overrings. For a module M, we also show that all essential extensions of M satisfying C ₁₁ are essential extensions of C ₁₁-modules constructed from M and certain subsets of idempotent elements of the ring of endomorphisms of the injective hull of M. Finally, we prove that if M is a C ₁₁-module, then so is its rational hull. Examples are provided to illustrate and delimit the theory.     

Synthesis of C3N4 crystals under high pressure and high temperature

C₃N₄ crystals with the size of several micrometers have been synthesized from C₃N₄H₄ in the presence of nickel-based alloy or cobalt as catalyst under high pressure of 7 GPa and temperature of about 1400°C for 10 min. Scanning electron microscopy, energy-disperse X-ray analysis, and X-ray diffraction were used to examine the grown crystals. The general rule on selecting the starting materials for synthesis of carbon nitride crystals at high pressures and high temperatures is suggested.     

Crank–Nicolson Scheme for Abstract Linear Systems

This paper studies the Crank–Nicolson discretization scheme for abstract differential equations on a general Banach space. We show that a time-varying discretization of a bounded analytic C₀-semigroup leads to a bounded discrete-time system. On Hilbert spaces, this result can be extended to all bounded C₀-semigroups for which the inverse generator generates a bounded C₀-semigroup. The presentation is based on C₀-semigroup theory and uses a functional analysis approach.     

First-principles calculations on electronic, chemical bonding and optical properties of tetragonal SrHfO3

Electronic, chemical bonding and optical properties of tetragonal SrHfO₃ were investigated using the plane-wave ultrasoft pseudopotential technique based on the first-principles density functional theory (DFT). The optimized equilibrium lattice parameters of tetragonal SrHfO₃ are in good agreement with experimental values. Band structure, densities of states (DOS), charge densities and molecular-orbital bonding structure of tetragonal SrHfO₃ have been obtained. The band structure shows that tetragonal SrHfO₃ has direct band gap. The DOS and charge densities indicate that bonding between Hf and O is mainly covalent due to Hf 5d and O 2p hybridization and that bonding between Sr and O is mainly ionic. The complex dielectric function, absorption coefficient, energy-loss spectrum, complex conductivity function and reflectivity of tetragonal SrHfO₃ have been predicted. The imaginary and real parts of the calculated complex dielectric functions are consistent with the experimental observations.     

The P1 and P2 approximations of the spherical harmonic method as applied to radiative heat transfer computations with allowance for strong blowing from the surface of a vehicle moving in the Jovian atmosphere

The spherical harmonics method in the P₁ and P₂ approximations is used to analyze radiative heat transfer for a space vehicle entering a planet’s atmosphere. Strong blowing of ablated materials from the vehicle surface is taken into account by using a two-layer flow model without allowance for the viscosity and thermal conduction of the gas. The heating and ablation of a multilayered thermal protection system are determined simultaneously with the vehicle’s flight trajectory, which is calculated taking into account the mass loss due to the ablation. The approach is illustrated by computing the flight of a space vehicle shaped as a spherical segment or a spherically blunted cone entering the Jovian atmosphere at a speed of 60 km/s and an entry angle of ?5°.     

Frequency and Time Domain Analysis of an Aeroelastic Wing Multiple Component Structure

A multiple component structure consisting of two Euler-Bernoulli beams connected to a rigid mass is used to model the heave dynamics of a wing micro air vehicle. In the time domain, the attainment of a C ₀-semigroup in the context of sesquilinear forms is demonstrated. In addition, the closed loop system is demonstrated to generate an exponentially stable C ₀-semigroup. In the frequency domain, the infinite dimensional transfer function is determined and used to examine several properties of the system. Finally, an optimal control is used to morph the wings to a desired shape, and simulation results are demonstrated.     

Influence of SiO2 in SiCp on the microstructure and impact strength of Al/SiCp composites fabricated by pressureless infiltration

The effect of SiO₂ in SiC_p and the following processing parameters on the microstructure and impact strength of Al/SiC_p composites fabricated by pressureless infiltration was investigated: Mg content in the aluminum alloy, SiC particle size, and holding time. Preforms of SiC_p in the form of rectangular bars (10 × 1 × 1 cm) were infiltrated at 1150°C in an argon→nitrogen atmosphere for 45 and 60 min by utilizing two aluminum alloys (Al-6 Mg-11 Si and Al-9 Mg-11 Si, wt.%). The results obtained show that the presence of SiO₂ in SiC affects the microstructure and impact strength of the composites significantly. When Al₄C₃ is formed, the impact strength decreases. However, a high proportion of SiC to SiO₂ limits the formation of the unwanted Al₄C₃ phase in the composites. Also, a higher content of Mg in the Al alloy lowers the residual porosity and, consequently, increases the composite strength. The impact strength grows with decrease in SiC particle size and increases considerably when the residual porosity is less than 1%. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 3, pp. 401–418, May–June, 2006.     

A (C o)-group generated by the lévy laplacian

In this paper, we discuss a (C _o)-group generated by the Lévy Laplacian acting on a domain in the space of Hida distributions. We also give a relationship between the analytic extension of this (C _o)-group and the adjoint operator of an infinite dimensional Fourier-Mehler transform introduced by H.- H. Kuo     

Three-dimensional data transfer operators in large plasticity deformations using modified-SPR technique

In this paper, the data transfer operators are developed in 3D large plasticity deformations using superconvergent patch recovery (SPR) method. The history-dependent nature of plasticity problems necessitates the transfer of all relevant variables from the old mesh to new one, which is performed in three main stages. In the first step, the history-dependent internal variables are transferred from the Gauss points of old mesh to nodal points. The variables are then transferred from nodal points of old mesh to nodal points of new mesh. Finally, the values are computed at the Gauss points of new mesh using their values at nodal points. As the solution procedure, in general, cannot be re-computed from the initial configuration, it is continued from the previously computed state. In particular, the transfer operators are defined for mapping of the state and internal variables between different meshes. Aspects of the transfer operators are presented by fitting the best polynomial function with the C₀, C₁ and C₂ continuity in 3D superconvergent patch recovery technique. Finally, the efficiency of the proposed model and computational algorithms is demonstrated through numerical examples.