6,181 research outputs found
Comment on "Dynamic Scaling of Non-Euclidean Interfaces" [arXiv:0804.1898]
This is the revised version of a Comment on a paper by C. Escudero (Phys.
Rev. Lett. 100, 116101, 2008; arXiv:0804.1898)
Anti-Coarsening and Complex Dynamics of Step Bunches on Vicinal Surfaces during Sublimation
A sublimating vicinal crystal surface can undergo a step bunching instability
when the attachment-detachment kinetics is asymmetric, in the sense of a normal
Ehrlich-Schwoebel effect. Here we investigate this instability in a model that
takes into account the subtle interplay between sublimation and step-step
interactions, which breaks the volume-conserving character of the dynamics
assumed in previous work. On the basis of a systematically derived continuum
equation for the surface profile, we argue that the non-conservative terms pose
a limitation on the size of emerging step bunches. This conclusion is supported
by extensive simulations of the discrete step dynamics, which show breakup of
large bunches into smaller ones as well as arrested coarsening and periodic
oscillations between states with different numbers of bunches.Comment: 26 pages, 11 figure
Dynamic phase transitions in electromigration-induced step bunching
Electromigration-induced step bunching in the presence of sublimation or
deposition is studied theoretically in the attachment-limited regime. We
predict a phase transition as a function of the relative strength of kinetic
asymmetry and step drift. For weak asymmetry the number of steps between
bunches grows logarithmically with bunch size, whereas for strong asymmetry at
most a single step crosses between two bunches. In the latter phase the
emission and absorption of steps is a collective process which sets in only
above a critical bunch size and/or step interaction strength.Comment: 4 pages, 4 figure
Persistence of Kardar-Parisi-Zhang Interfaces
The probabilities that a growing Kardar-Parisi-Zhang interface
remains above or below the mean height in the time interval are
shown numerically to decay as with and . Bounds on are
derived from the height autocorrelation function under the assumption of
Gaussian statistics. The autocorrelation exponent for a
--dimensional interface with roughness and dynamic exponents and
is conjectured to be . For a recently proposed
discretization of the KPZ equation we find oscillatory persistence
probabilities, indicating hidden temporal correlations.Comment: 4 pages, 3 figures, uses revtex and psfi
Kinetics of step bunching during growth: A minimal model
We study a minimal stochastic model of step bunching during growth on a
one-dimensional vicinal surface. The formation of bunches is controlled by the
preferential attachment of atoms to descending steps (inverse Ehrlich-Schwoebel
effect) and the ratio of the attachment rate to the terrace diffusion
coefficient. For generic parameters () the model exhibits a very slow
crossover to a nontrivial asymptotic coarsening exponent .
In the limit of infinitely fast terrace diffusion () linear coarsening
( = 1) is observed instead. The different coarsening behaviors are
related to the fact that bunches attain a finite speed in the limit of large
size when , whereas the speed vanishes with increasing size when .
For an analytic description of the speed and profile of stationary
bunches is developed.Comment: 8 pages, 10 figure
Scaling properties of step bunches induced by sublimation and related mechanisms: A unified perspective
This work provides a ground for a quantitative interpretation of experiments
on step bunching during sublimation of crystals with a pronounced
Ehrlich-Schwoebel (ES) barrier in the regime of weak desorption. A strong step
bunching instability takes place when the kinetic length is larger than the
average distance between the steps on the vicinal surface. In the opposite
limit the instability is weak and step bunching can occur only when the
magnitude of step-step repulsion is small. The central result are power law
relations of the between the width, the height, and the minimum interstep
distance of a bunch. These relations are obtained from a continuum evolution
equation for the surface profile, which is derived from the discrete step
dynamical equations for. The analysis of the continuum equation reveals the
existence of two types of stationary bunch profiles with different scaling
properties. Through a mathematical equivalence on the level of the discrete
step equations as well as on the continuum level, our results carry over to the
problems of step bunching induced by growth with a strong inverse ES effect,
and by electromigration in the attachment/detachment limited regime. Thus our
work provides support for the existence of universality classes of step
bunching instabilities [A. Pimpinelli et al., Phys. Rev. Lett. 88, 206103
(2002)], but some aspects of the universality scenario need to be revised.Comment: 21 pages, 8 figure
Breakdown of step-flow growth in unstable homoepitaxy
Two mechanisms for the breakdown of step flow growth, in the sense of the
appearance of steps of opposite sign to the original vicinality, are studied by
kinetic Monte Carlo simulations and scaling arguments. The first mechanism is
the nucleation of islands on the terraces, which leads to mound formation if
interlayer transport is sufficiently inhibited. The second mechanism is the
formation of vacancy islands due to the self-crossing of strongly meandering
steps. The competing roles of the growth of the meander amplitude and the
synchronization of the meander phase are emphasized. The distance between
vacancy islands along the step direction appears to be proportional to the
square of the meander wavelengthComment: 7 pages, 9 figure
Entrepreneurship by Alliance
Recent years have seen the introduction of markets and a system of private property rights in China with a view to changing the composition of production and demand and enhancing welfare. Central to the success of these reforms is the rise of entrepreneurship with its potential to set the economy on a higher growth path by supplying the products which consumers need and want, creating new employment opportunities, and introducing new and more efficient technologies of production. But to what extent can we expect to see entrepreneurs in China behaving like their counterparts in the advanced industrial economies of Western Europe, Japan, and the United States? This is the question we address in this chapter. In our view, the reform programme has, indeed, opened up new opportunities for private enterprise activity; but idiosyncrasies of the business environment are at the same time generating novel institutional arrangements in support of entrepreneurs' investments. We agree, therefore, with Herrick and Kindleberger when they assert that "Development ought not to be viewed as a monotonic, stylized path, ever onward and upward, historically established and invariably repeated" (1983, p.62).entrepreneurship;economic growth;economic development;business networking;Western economies
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