Formation of graphene on Ru（0001） surface

We report on the formation of a graphene monolayer on a Ru(0001) surface by annealing the Ru(0001) crystal. The samples are characterized by scanning tunnelling microscopy (STM) and Auger electron spectroscopy (AES). STM images show that the Moir\'{e} pattern is caused by the graphene layer mismatched with the underlying Ru(0001) surface and has an $N\times N$ superlattice. It is further found that the graphene monolayer on a Ru(0001) surface is very stable at high temperatures. Our results provide a simple and convenient method to produce a graphene monolayer on the Ru(0001) surface, which is used as a template for fabricating functional nanostructures needed in future nano devices and catalysis.     

Electronic structures and coronene on Ru（0001）： vibrational properties of first-principles study

We calculate the configurations,electronic structures,vibrational properties at the coronene/Ru(0001) interface,and adsorption of a single Pt atom on coronene/Ru(0001) based on density functional theory calculations.The geometric structures and electronic structures of the coronene on Ru(0001) are compared with those of the graphene/Ru(0001).The results show that the coronene/Ru(0001) can be a simplified model system used to describe the interaction between graphene and ruthenium.Further calculations of the vibrational properties of coronene molecule adsorbed on Ru(0001) suggest that the phonon properties of differently corrugated regions of graphene on Ru(0001) are different.This model system is also used to investigate the selective adsorption of Pt atoms on graphene/Ru(0001).The configurations of Pt on coronene/Ru(0001) with the lowest binding energy give clues to explain the experimental observation that a Pt cluster selectively adsorbs on the second highest regions of graphene/Ru(0001).This work provides a simple model for understanding the adsorption properties and vibrational properties of graphene on Ru(0001) substrate.     

Two-Step Growth of MgO Films on Sapphire （0001） Substrates by Radio Frequency Plasma-Assisted Molecular Beam Epitaxy

We report on the growth of rock salt MgO films on sapphire (0001) substrates by rf plasma-assisted molecular beam epitaxy.A two-step method,i.e.high temperature epilayer growth after low-temperature buffer layer growth,was adopted to obtain the single crystal MgO film.The epitaxial orientation between the MgO epilayer and the sapphire (0001) substrate was studied by using in situ reflection high energy electron diffraction and ex situ x-ray diffraction,and it is found that the MgO film grows with [111] orientation.The role of the low temperature buffer layer in the improvement of crystal quality of the MgO epilayer is discussed based on the cross-sectional scanning electron microscopy.     

Ge BEAM TREATMENT OF Si SUBSTRATE FOR MOLECULAR BEAM EPITAXY

A new surface cleaning method for Si MBE is described in which a very weak Ge beam flux is deposited on the surface for removing the thin passivative layer of SiO₂ on the Si subetrate. It has proved that the SiO₂ will react with Ge at a relatively low temperature (620℃), and as a result, the oxide layer becomes volatile. Here the high temperature annealing in the conventional Shiraki method is no longer required, and since the oxide layer is removed in ultra high vacuum, only very little carbon contamination may occur. Furthermore, to reduce the excessive Ge on the substrate surface, Ge is deposited at 620℃ and then the sample is annealed at 700℃; the residual Ge atoms on Si substrate can be reduced to less than 0.1 monolay-er (ML). Ge beam treatment turns out to be an effective low-temperature Si surface-cleaning method, especially for the heteroepitaxial growth of Ge_xSi_1-x/Si.     

Adsorption behavior of iron phthalocyanine on a Ag（110） surface

An investigation on the growth behavior of FePc on a Ag(110) surface is carried out by using scanning tunneling microscopy(STM).At an FePc coverage of 3.5 ML,an ordered superstructure(densely packed) with a lateral shift is observed.The densely packed superstructure can be attributed to the substrate commensuration and the intermolecular van der Waals attractive interaction.The in-plane lateral shift in the superphase is specifically along the direction of [10] azimuth.The results provide a new perspective to understanding the intermolecular and the molecule-substrate interactions.     

CO吸附对乙醛在Co(0001)表面降解和多聚的影响

The adsorption and reaction of acetaldehyde on the clean and CO pre-covered Ru(0001) surfaces have been investigated using temperature programmed desorption method. On the clean Ru(0001) surface, the decomposition of acetaldehyde is the main reaction channel, with little polymerization occurring. However, on the CO pre-covered Ru(0001) surface, the decomposition of acetaldehyde is inhibited considerably with increasing CO coverage. Whereas, the polymerization occurs efficiently, especially at high CO coverage (θ_CO>0.5 ML), which is strongly CO coverage dependent. Combined with previous studies, the well-ordered hexagonal structure of CO layer formed on the Ru(0001) surface at high CO coverage that matches the configuration of paraldehyde is likely to be the origin of this remarkable phenomenon.     

Influence of double A1N buffer layers on the qualities of GaN films prepared by metal-organic chemical vapour deposition

<正>In this paper we report that the GaN thin film is grown by metal-organic chemical vapour deposition on a sapphire (0001) substrate with double AlN buffer layers.The buffer layer consists of a low-temperature(LT) AlN layer and a high-temperature(HT) AlN layer that are grown at 600℃and 1000℃,respectively.It is observed that the thickness of the LT-AlN layer drastically influences the quality of GaN thin film,and that the optimized 4.25-min-LT-AlN layer minimizes the dislocation density of GaN thin film.The reason for the improved properties is discussed in this paper.     

Growth of high quality InSb thin films on GaAs substrates by molecular beam epitaxy method with AlInSb/GaSb as compound buffer layers

A series of In Sb thin films were grown on Ga As substrates by molecular beam epitaxy(MBE).Ga Sb/Al In Sb is used as a compound buffer layer to release the strain caused by the lattice mismatch between the substrate and the epitaxial layer,so as to reduce the system defects.At the same time,the influence of different interface structures of Al In Sb on the surface morphology of buffer layer is explored.The propagation mechanism of defects with the growth of buffer layer is compared and analyzed.The relationship between the quality of In Sb thin films and the structure of buffer layer is summarized.Finally,the growth of high quality In Sb thin films is realized.     

Simulation of multilayer Cu/Pd（100） heteroepitaxial growth by pulse laser deposition

The heteroepitaxial growth of multilayer Cu/Pd(100) thin film via pulse laser deposition (PLD) at room temperature is simulated by using kinetic Monte Carlo (KMC) method with realistic physical parameters. The effects of mass transport between interlayers, edge diffusion of adatoms along the islands and instantaneous deposition are considered in the simulation model. Emphasis is placed on revealing the details of multilayer Cu/Pd(100) thin film growth and estimating the Ehrlich--Schwoebel (ES) barrier. It is shown that the instantaneous deposition in the PLD growth gives rise to the layer-by-layer growth mode, persisting up to about 9 monolayers (ML) of Cu/Pd(100). The ES barriers of The heteroepitaxial growth of multilayer Cu/Pd（100） thin film via pulse laser deposition （PLD） at room temperature is simulated by using kinetic Monte Carlo （KMC） method with realistic physical parameters. The effects of mass transport between interlayers, edge diffusion of adatoms along the islands and instantaneous deposition are considered in the simulation model, Emphasis is placed on revealing the details of multilayer Cu/Pd（100） thin film growth and estimating the Ehrlich-Schwoebel （ES） barrier. It is shown that the instantaneous deposition in the PLD growth gives rise to the layer-by-layer growth mode, persisting up to about 9 monolayers （ML） of Cu/Pd（100）. The ES barriers of 0.08 ± 0.01 eV is estimated by comparing the KMC simulation results with the real scanning tunnelling microscopy （STM） measurements,     

Electronic structure and magnetic properties of Fe andc(2×2)FeCr overlayers deposited on Cr(100)

Ab initio spin-polarized calculations of the electronic structure of Fe overlayers on the Cr(100) substrate were performed using full-potential LAPW method. There was found that the magnetic moment of Fe monolayer on Cr(100) aligned antiferromagnetically with respect to the interface Cr layer and is equal 2.48 μ_B. The dependence on the Fe film thickness of spin-density distribution near the surface and Fe-Cr interface, is analysed. The stability of CrFec(2 × 2) substitutional surface alloy on Cr(100) substrate is studied on the basis of electronic structure calculations. The total energy calculations show that Fe monolayer is unstable against the CrFec(2 × 2) surface alloy formation with ferromagnetic ordering in the layer. Presented at the VIII-th Symposium on Surface Physics, Třešt’ Castle, Czech Republic, June 28 – July 2, 1999.     

First Observation of the nu(17)-nu(4) Difference Bands of Diborane (10)B(2)H(6) and (11)B(2)H(6)

An analysis of the nu(17)-nu(4) difference bands near 800 cm(-1) of two isotopic species, (10)B(2)H(6) and (11)B(2)H(6), of diborane has been carried out using infrared spectra recorded with a resolution of ca. 0.003 cm(-1). In addition, the nu(17) band of (10)B(2)H(6) has been recorded and assigned. Since this band in (11)B(2)H(6) had already been studied (R. L. Sams, T. A. Blake, S. W. Sharpe, J.-M. Flaud, and W. J. Lafferty, J. Mol. Spectrosc. 191, 331-342 (1998)), it was possible to derive precise energy levels and Hamiltonian constants for the 4(1) vibrational states of both isotopic species. Copyright 2000 Academic Press.     

The 2(3)Delta(g) State of (7)Li(2)

Using pulsed perturbation-facilitated optical-optical double resonance (PFOODR) spectroscopy, the 2(3)Delta(g) state of (7)Li(2) (electronic configuration (varsigma(g)2s) (4ddelta(g)), effective principal quantum number n* = 4.101) has been observed and assigned. Molecular constants and a RKR potential energy curve were obtained. The major molecular constants are Copyright 2000 Academic Press.     

Rovibrational Intensities of the (00(0)3) <-- (10(0)0) Dyad Absorption Bands of (12)C(16)O(2)

Absolute line intensities of (12)C(16)O(2) are experimentally measured for the first time for the (00(0)3)(I) <-- (10(0)0)(II) band at 5687.17 cm(-1) and the (00(0)3)(I) <-- (10(0)0)(I) band at 5584.39 cm(-1). The spectra were obtained using a Bomem DA8 Fourier transform spectrometer and a 25-m base-path White cell at NASA-Ames Research Center. The rotationless bandstrengths at a temperature of 296 K and the Herman-Wallis parameters are S(0)(vib) = 6.68(30) x 10(-25) cm(-1)/(molecule/cm(2)); A(1) = 1.4(9) x 10(-4), and A(2) = -1.1(5) x 10(-5) for the (00(0)3)(I) <-- (10(0)0)(II) band and S(0)(vib) = 6.07(22) x 10(-25) cm(-1)/(molecule/cm(2)); A(1) = 5.2(1.5) x 10(-4) and A(2) = -4.0(7) x 10(-5) for the (00(0)3)(I) <-- (10(0)0)(I) band.     

Theoretical Study of the Collision-Induced Double Transition CO(2) (nu(3) = 1) + N(2) (nu(1) = 1) <-- CO(2) (nu(3) = 0) + N(2) (nu(1) = 0) at 296 K

A procedure is presented for the calculation of the double vibrational collision-induced absorption CO(2) (nu(3) = 1) + N(2) (nu(1) = 1) <-- CO(2) (nu(3) = 0) + N(2) (nu(1) = 0) on the basis of quantum lineshapes computed using an isotropic potential and dipole-induced dipole functions. The linestrengths and energies of the vibration-rotation transitions are treated explicitly for N(2), utilizing the HITRAN database for CO(2). The theoretical absorption profile is compared to recent experimental results. By narrowing the width of the individual lines contributing to the overall absorption profile relative to their values determined for N(2)-N(2) collision-induced absorption, excellent agreement between theory and experiment is obtained. Copyright 2000 Academic Press.     

The Perturbation between the G(1)Pi(g) and 2(1)Delta(g) States of (7)Li(2)

We have observed the rotational levels in the v = 2, 3, 5, 6, 7, and 8 vibrational manifolds of the 2(1)Delta(g) state of (7)Li(2) via the A(1)Sigma(+)(u) intermediate levels by DeltaLambda = 2 transitions. This violation of the DeltaLambda = 0, +/-1 selection rule is due to the interaction with the G(1)Pi(g) state. Band-by-band deperturbations of the G(1)Pi(g) approximately 2(1)Delta(g) (v(Pi), v(Delta)) = (11, 2), (12, 3), (15, 5), (16, 6), (18, 7), and (19, 8) bands have been performed. Deperturbed molecular constants and rotational-electronic interaction parameters are reported here. Copyright 2000 Academic Press.     

The v(1)+v(3) Bands of the (16)O(17)O(16)O and (16)O(16)O(17)O Isotopomers of Ozone

Using 0.002 cm(-1) resolution Fourier transform absorption spectra of an (17)O enriched ozone sample, an extensive analysis of the v(1)+v(3) bands of the (16)O(17)O(16)O and (16)O(16)O(17)O isotopomers of ozone has been performed for the first time. The experimental rotational levels of the (101) vibrational states were satisfactorily reproduced using a Hamiltonian matrix that takes into account the observed rovibrational resonances. More precisely, for (16)O(17)O(16)O, as for the other C(2v)-type ozone isotopomers, it was necessary to account for the Coriolis type resonances linking the (101) rotational levels with the levels of the (200) and (002) vibrational states and the Darling-Dennison interaction coupling the levels of (200) with those of (002). For the C(s)-type isotopomer, namely (16)O(16)O(17)O, as for (16)O(16)O(18)O and (16)O(18)O(18)O, it proved necessary to also account for an additional DeltaK(a)&equals+/-2 resonance involving the rotational levels from (101) and (002) (J.-M. Flaud and R. Bacis, Spectrochimica Acta Part A 54, 3-16 (1998)). Using a Hamiltonian matrix which takes these resonances explicitly into account, precise vibrational energies and rotational and coupling constants were deduced, leading to the following band centers: v(0)(v(1)+v(3))=2078.3496 cm(-1) for (16)O(17)O(16)O and v(0)(v(1)+v(3))=2098.8631 cm(-1) for (16)O(16)O(17)O. Copyright 2001 Academic Press.     

N(2)-Broadening Coefficients in the nu(1) Band of (35)Cl(12)C(14)N

N(2)-broadening coefficients have been measured for 30 lines of cyanogen chloride ((35)Cl(12)C(14)N) at room temperature in the P and R branches of the nu(1) band, using a tunable diode-laser spectrometer. These lines, with J values ranging from 0 to 55, are located in the spectral range 694-736 cm(-1). The collisional widths are obtained by fitting the spectral lines with a Voigt and a Rautian profile. The broadenings coefficients of (35)ClCN-N(2) have also been calculated from a semiclassical theory involving the atom-atom Lennard-Jones model for the intermolecular potential in addition to electrostatic interaction. Copyright 2000 Academic Press.     

CO2同位素分子16O12C16O, 16O12C17O, 16O13C17O配分函数研究

本文主要研究了CO2的三种同位素分子16O12C16O , 16O12C17O ,16O13C17O 70 K~6000 K的总内配分函数 (TIPS)。在总内配分函数的计算中, 转动配分函数的计算采用了McDowell的解析式法, 振动配分函数则采用了简谐振动近似(HOA)获得。最后通过将两配分函数乘积近似计算得出TIPS, 并将其70~3000 K的数据和HITRAN04数据进行了比较, 发现所得结果和数据库符合的较好, 且其误差可以近似看成一条直线。并通过对误差的拟合修订了高温区(3000~6000 K)的计算数据, 给出了在高温下的较为准确的TIPS值。     

Torsional Splitting in the nu(5) Fundamental Infrared Band of CH(3)CD(3) and (13)CH(3)CD(3)

The nu(5) fundamental (C-C stretching) of CH(3)CD(3) shows a resolved torsional structure, caused by perturbations due mainly to the linear dependence of the torsional potential barrier on the normal coordinate Q(5). We were able to analyze this structure and to assign vibration-rotation transition wavenumbers for all five torsional components, classified according to the symmetry species of the G(18)((3)) extended molecular group. The torsional splitting pattern is qualitatively similar to that of a nondegenerate vibrational state with an even number of excited torsional quanta v(6). Explorative calculations show that the main perturber system should consist of the torsional components of the vibrational ground state correlating with v(6)=4 in the high barrier limit. The strength of the perturbation on the E(r0) torsional components of nu(5) increases rapidly with r, the E(40) component being the most affected. The observed transition wavenumbers can be reasonably fitted by a simplified model containing independent effective vibration-rotation parameters for the five different torsional components of nu(5), for both CH(3)CD(3) and (13)CH(3)CD(3). The trend of the determined values of the effective vibrational wavenumbers and rotational parameters over the torsional components supports the proposed vibration-torsion interaction mechanism, responsible for the observed torsional splittings. A strong anomaly observed in the rotational intensity distribution of nu(5) is discussed. Copyright 2001 Academic Press.