共查询到20条相似文献,搜索用时 31 毫秒
1.
A kinetic Monte Carlo investigation of island nucleation and growth in thin-film epitaxy in the presence of substrate-mediated interactions 总被引:3,自引:0,他引:3
K.A. Fichthorn M.L. Merrick M. Scheffler 《Applied Physics A: Materials Science & Processing》2002,75(1):17-23
Island nucleation and growth during thin-film epitaxy is typically described using mean-field rate equations, which can be
solved to predict the density of stable islands as a function of the deposition rate and the diffusivity of an isolated adatom.
Recent theoretical and experimental studies indicate that medium- and long-range interactions between adatoms may change the
simple picture that nucleation theory provides, because the presence of these interactions invalidates some of its assumptions.
In this work, we investigate the ramifications of medium-range, substrate-mediated interactions for aspects of island nucleation
and growth. The interactions are quantified for Ag on a strained Ag (111) substrate using density-functional-theory calculations.
We discuss our incorporation of these interactions into a kinetic Monte Carlo model to study thin-film epitaxy. The simulated
thin-film growth is compared to predictions by standard nucleation theory. We discuss features of island nucleation and growth
that are actuated by the presence of medium-range interactions.
Received: 30 April 2001 / Accepted: 23 July 2001 / Published online: 3 April 2002 相似文献
2.
Sen-yue Lou Ji Lin Xiao-yan Tang 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(4):473-478
The Painlevé integrability of the 2+1 dimensional AKNS system is proved. Using the standard truncated Painlevé expansion which
corresponds to a special B?cklund transformation, some special types of the localized excitations like the solitoff solutions,
multi-dromion solutions and multi-ring soliton solutions are obtained.
Received 31 January 2001 and Received in final form 15 May 2001 相似文献
3.
S. Miyashita E. Vincent 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(2):203-211
Aging in spin glasses (and in some other systems) reveals astonishing effects of `rejuvenation and memory' upon temperature
changes. In this paper, we propose microscopic mechanisms (at the scale of spin-spin interactions) which can be at the origin
of such phenomena. Firstly, we recall that, in a frustrated system, the effective average interaction between two spins may take different values (possibly with opposite signs) at different temperatures. We give simple examples
of such situations, which we compute exactly. Such mechanisms can explain why new ordering processes (rejuvenation) seem to take place in spin glasses when the temperature is lowered. Secondly, we emphasize the fact that inhomogeneous interactions do naturally lead to a wide distribution of relaxation times for thermally activated flips. `Memory spots' spontaneously
appear, in the sense that the flipping time of some spin clusters becomes extremely long when the temperature is decreased.
Such memory spots are capable of keeping the memory of previous ordering at a higher temperature while new ordering processes occur at a lower temperature. After a qualitative
discussion of these mechanisms, we show in the numerical simulation of a simplified example that this may indeed work. Our
conclusion is that certain chaos-like phenomena may show up spontaneously in any frustrated and inhomogeneous magnetic system, without impeding the occurrence of memory effects.
Received 5 February 2001 and Received in final form 27 April 2001 相似文献
4.
D. Guo K. Cai L.-T. Li Y. Huang Z.-L. Gui 《Applied Physics A: Materials Science & Processing》2002,74(1):69-72
Diamond-like-carbon (DLC) films have been deposited on Si, aluminum and indium tin oxide-coated glass from several organic
solvents with pulse-modulated power. The films are characterized by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.
XPS spectra show that the main composition of the films is carbon and Raman spectra show that the films are typical DLC films
and a high potential is preferable in the formation of sp
3-structure carbon. Comparing the results from different solvents and different substrates we deduce that the methyl group
of the solvents has a critical function in forming the DLC films. However, the formation process and the characters of the
films, such as appearance, resistivity and thickness, are mainly determined by the substrate. We may call this deposition
a substrate-controlled reaction.
Received: 31 May 2000 / Accepted: 9 January 2001 / Published online: 3 April 2001 相似文献
5.
O. Betbeder-Matibet M. Combescot 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(4):505-516
The correct treatment of the close-to-boson character of excitons is known to be a major problem. In a previous work, we have
proposed a “commutation technique” to include this close-to-boson character in their interactions. We here extend this technique
to excitons with spin degrees of freedom as they are of crucial importance for many physical effects. Although the exciton
total angular momentum may appear rather appealing at first, we show that the electron and hole angular momenta are much more
appropriate when dealing with scattering processes. As an application of this commutation technique to a specific problem,
we reconsider a previous calculation of the exciton-exciton scattering rate and show that the proposed quantity is intrinsically
incorrect for fundamental reasons linked to the fermionic nature of the excitons.
Received 25 October 2001 Published online 25 June 2002 相似文献
6.
V.S. Gerdjikov 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):237-241
We compare the Hamiltonian properties of the N-soliton solutions of the NLSE in the adiabatic approximation and show how it matches the Hamiltonian formulation for the
complex Toda chain which describes the adiabatic N-soliton interactions.
Received 21 October 2001 Published online 2 October 2002
RID="a"
ID="a"e-mail: gerjikov@inrne.bas.bg 相似文献
7.
M. Johansson A.M. Morgante S. Aubry G. Kopidakis 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):279-283
Modulational instability of travelling plane waves is often considered as the first step in the formation of intrinsically
localized modes (discrete breathers) in anharmonic lattices. Here, we consider an alternative mechanism for breather formation,
originating in oscillatory instabilities of spatially periodic or quasiperiodic nonlinear standing waves (SWs). These SWs
are constructed for Klein-Gordon or Discrete Nonlinear Schr?dinger lattices as exact time periodic and time reversible multibreather
solutions from the limit of uncoupled oscillators, and merge into harmonic SWs in the small-amplitude limit. Approaching the
linear limit, all SWs with nontrivial wave vectors (0 < Q < π) become unstable through oscillatory instabilities, persisting for arbitrarily small amplitudes in infinite lattices.
The dynamics resulting from these instabilities is found to be qualitatively different for wave vectors smaller than or larger
than π/2, respectively. In one regime persisting breathers are found, while in the other regime the system thermalizes.
Received 6 October 2001 / Received in final form 1st March 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: mjn@ifm.liu.se 相似文献
8.
A. Pumir V.V. Barelko 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,22(1):71-77
Fronts of weakly exothermal chemical reaction may propagate in solids at very low temperatures ( 4K≤T≤77K) thanks to a quite unusual mechanism, involving a feedback between the heat produced by the reaction and the disruption of
the solid matrix. In this class of phenomena, the reaction may be induced by mechanical constraints, without a large elevation
of temperature. On the basis of a simple phenomenological model, we investigate ignition of a propagating front by initially
(i) disrupting a localized zone of the solid matrix, or by (ii) introducing a temperature jump, leading to a thermal shock
with strong temperature gradients. In particular, we show that reaction can be initiated by disrupting only a very small fraction
of the sample. Applications to the problem of initiation of solid explosives by friction or shocks is briefly discussed.
Received 26 January 2001 and Received in final form 3 May 2001 相似文献
9.
K.T. Stoychev M.T. Primatarowa K. Marinov 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):301-304
Effects of the exciton and polariton dispersions and the nonlinear exciton and photon interactions on the properties of polariton
solitons in molecular crystals are investigated. Higher-order terms and phase-modulation (chirp) are taken into account. Bright-
and dark-soliton solutions of the resulting modified nonlinear Schr?dinger (NLS) equation are presented. Nonlinearity- and
dispersion-induced critical points on the polariton dispersion curve are obtained, separating regions with different solutions.
Received 2 October 2001 / Received in final form 23 May 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: Stoychev@issp.bas.bg 相似文献
10.
Ph. Ebert 《Applied Physics A: Materials Science & Processing》2002,75(1):101-112
This work reports the measurement of the nano-scale physical properties of surface vacancies and the extraction of the types
and concentrations of dopant atoms and point defects inside compound semiconductors, primarily by cross-sectional scanning
tunneling microscopy on cleavage surfaces of III–V semiconductors. The results provide the basis to determine the physical
mechanisms governing the interactions, the formation, the electronic properties, and the compensation effects of surface as
well as bulk point defects and dopant atoms.
Received: 10 May 2001 / Accepted: 23 July 2001 / Published online: 3 April 2002 相似文献
11.
V.V. Glagolev K.G. Gulamov V.D. Lipin S.L. Lutpullaev K. Olimov Kh.K. Olimov A.A. Yuldashev B.S. Yuldashev 《The European Physical Journal A - Hadrons and Nuclei》2001,11(3):285-296
The data on investigation of inelastic interactions of 16O nuclei in a hydrogen bubble chamber at an incident momentum of 3.25 A GeV/c are presented. Separate characteristics as fragments isotope composition and topological cross-sections of fragmentation
channels are given. The processes of formation of light fragments and unstable nuclei, and the break-up of the 16O nucleus into multicharge fragments are investigated. A comparison between the experimental data and the calculations of
the cascade fragmentation evaporation model (CFEM) is made. The observed singularities of the interactions point out the important
role of the nucleus α-cluster structure in the formation of the final products.
Received: 9 January 2001 / Accepted: 13 June 2001 相似文献
12.
M.E. Gouvêa A.S.T. Pires 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(2):147-153
We use the self-consistent harmonic approximation (SCHA) to study the two-dimensional classical Heisenberg anisotropic (easy-plane)
ferromagnetic model including nearest- and next-nearest neighbor exchange interactions. For temperatures much lower than the
Kosterlitz-Thouless phase transition temperature T
KT, spin waves must be the most relevant excitations in the system and the SCHA must account for its behavior. However, for
temperatures near T
KT, we should expect vortex pairs to be quite important. The effect of these vortex excitations on the phase transition temperature
is included in our theory as a renormalization of the exchange interactions. Then, combining the SCHA theory to the renormalization
effect due to vortex pairs, we calculate the dependence of T
KT as a function of the easy-plane anisotropies and exchange interactions.
Received 3 April 2001 and Received in final form 20 September 2001 相似文献
13.
We investigate stationary and travelling wave solutions of the classical one-dimensional transverse field Ising model. Results
are given on the existence, shape and stability of kink solutions and periodic solutions. We review recent analytical results
(e.g., the proof of existence of a one-parameter family of stationary kink solutions and the proof of existence of travelling wave
kink solutions with nonzero velocity c≠ 0) and extend them by the use of numerical methods. Small oscillations arising in the tails of travelling kink solutions
are investigated numerically. In the end, stability analysis puts some light on pinning effects.
Received 23 February 2001 and Received in final form 4 October 2001 相似文献
14.
G. Baym J.-P. Blaizot M. Holzmann F. Laloë D. Vautherin 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):107-124
We study the effects of repulsive interactions on the critical density for the Bose-Einstein transition in a homogeneous dilute
gas of bosons. First, we point out that the simple mean field approximation produces no change in the critical density, or
critical temperature, and discuss the inadequacies of various contradictory results in the literature. Then, both within the
frameworks of Ursell operators and of Green's functions, we derive self-consistent equations that include correlations in
the system and predict the change of the critical density. We argue that the dominant contribution to this change can be obtained
within classical field theory and show that the lowest order correction introduced by interactions is linear in the scattering
length, a, with a positive coefficient. Finally, we calculate this coefficient within various approximations, and compare with various
recent numerical estimates.
Received 15 July 2001 相似文献
15.
K.L. Yao G.Y. Sun W.Z. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(3):309-313
By using the density matrix renormalization group (DMRG) and the self-consistent numerical method, we obtain a high spin ground
state with localized spin density describing spin localization and the soliton describing the distortion of the lattice configurations
along the main chain. Different electron-phonon interactions result in different configurations of solitons. When the electron-phonon
coupling along the main chain is larger than a critical value , a transition from a single soliton-like distortion to a pair of soliton-like distortions along the main chain takes place.
Such critical value depends mainly on the intersite Coulomb interactions. The spin density wave along the main chain is always localized around
the center of soliton-like distortions.
Received 2 July 2001 and Received in final form 25 September 2001 相似文献
16.
J. Gemmer G. Mahler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(3):385-393
For a bi-partite quantum system defined in a finite dimensional Hilbert-space we investigate in what sense entanglement change
and interactions imply each other. For this purpose we introduce an entanglement-operator, which is then shown to represent
a non-conserved property for any bi-partite system and any type of interaction. This general relation does not exclude the
existence of special initial product states, for which the entanglement remains small over some period of time, despite interactions.
For this case we derive an approximation to the full Schr?dinger-equation, which allows the treatment of the composite systems
in terms of product states. The induced error is estimated. In this factorization-approximation one subsystem appears as an
effective potential for the other. A pertinent example is the Jaynes-Cummings model, which then reduces to the semi-classical
rotating wave approximation.
Received 8 June 2001 相似文献
17.
We have performed molecular-dynamics simulations to study the effect of an external electric field on a macroion in the solution
of multivalent Z : 1 salt. To obtain plausible hydrodynamics of the medium, we explicitly make the simulation of many neutral particles along
with ions. In a weak electric field, the macroion drifts together with the strongly adsorbed multivalent counterions along
the electric field, in the direction proving inversion of the charge sign. The reversed mobility of the macroion is insensitive
to the external field, and increases with salt ionic strength. The reversed mobility takes a maximal value at intermediate
counterion valence. The motion of the macroion complex does not induce any flow of the neutral solvent away from the macroion,
which reveals screening of hydrodynamic interactions at short distances in electrolyte solutions. A very large electric field,
comparable to the macroion unscreened field, disrupts charge inversion by stripping the adsorbed counterions off the macroion.
Received 5 December 2001 and Received in final form 10 April 2002 相似文献
18.
Yu.A. Fridman D.V. Spirin C.N. Alexeyev D.A. Matiunin 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):185-190
The possibility of the long-range magnetic order stabilization in two-dimensional ferromagnets with the account of dipolar
and magnetoelastic interactions is investigated. The mechanisms of the magnetic order stabilization by both types of interactions
are studied. The Curie temperature is estimated. The comparisons with experimental data are made.
Received 22 June 2001 and Received in final form 17 January 2002 相似文献
19.
R.A. Ganeev A.I. Ryasnyansky M.K. Kodirov S.R. Kamalov V.A. Li R.I. Tugushev T. Usmanov 《Applied physics. B, Lasers and optics》2002,75(1):47-51
The results of optical limiting investigations of cobalt-doped polyvinylpyrrolidone solutions are presented. The optical limiting
studies have shown that this process is due to self-defocusing at the wavelength of 1064 nm and also due to reverse saturable
absorption and self-defocusing at the wavelength of 532 nm. The results of measurements on the non-linear optical characteristics
of organometallic complexes are presented.
Received: 10 July 2001 / Revised version: 15 October 2001 / Published online: 29 November 2001 相似文献
20.
H. Zimmermann E. Richter C. Reichle I. Westphal P. Geggier U. Rehn S. Rogaschewski W. Bleiss G.R. Fuhr 《Applied Physics A: Materials Science & Processing》2001,73(1):11-26
During locomotion, adherently growing cells release highly ordered structures consisting of filaments and patches often dendritically
organised. Such traces can be re-incorporated by the donor cell or disconnected and lost. Here, we present the results of
a three-year research programme into trace formation and structural organisation including the influence of substrate surface
properties. Some phenomena may, ultimately, have medical or technological applications. These include: (i) the deposition
and re-incorporation of cellular material as cells move forward and backward; (ii) the ability of cells to differentiate between
their own and foreign traces; (iii) the presence of receptors in the intact membrane envelope of filaments and patches; and
(iv) the cytoplasmic content of patches. Trace formation is physiologically controlled and a characteristic of many types
of actively migrating higher animal and human cells. Possible applications and perspectives are discussed and the importance
of cell-trace elements as “bionanotubes” and biological submicron compartments of cells is explained.
Received: 5 February 2001 / Accepted: 6 February 2001 / Published online: 23 May 2001 相似文献