Growth kinematics of the regeneration surfaces of crystals (original) (raw)
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Journal of Applied Crystallography, 1979
The article deals with a method of analysis of the dl(t) curves giving the intensity variations of the light transmitted through a crystal face on which growth steps are spreading out. The method is based on the coupled investigation of both dl(t)and da(dl)/dt 3 and allows the characterization of the profile even when the crystal is weakly birefringent, and the determination of the spread velocity, both for a single step entering the measurement field and for a group of steps.
Progress in Crystal Growth and Characterization of Materials, 1998
Observations reported since 1980 on the kinetics of growth and surface morphology of crystals obtained from solutions are reviewed and interpreted from the standpoint of crystal growth theories. After a brief introduction to the theories of crystal growth, first the kinetics of growth are surveyed and confronted with the crystal growth theories. Here the origins of deviations in the linear (lependences of inclination of growth hillocks and rate of displacement of their growth steps on super saturation are analysed and explained in terms of kink nucleation at steps and solute accumulation at kinks. Thereafter the mechanisms of adsorption of impurities on growing crystal surfaces are briefly presented, and some typical experimental data on the kinetics of crystal growth in the presence of impurities and the tapering of KDP-type crystals are discussed in terms of the proposed mechmfisms. The general features of growth hillocks at isolated and composite dislocation sources are then described and discussed in relation to the morphological importance of as-grown faces and growth conditions. The latest results on the bunching of elementary steps and the formation and stability of macrosteps are subsequently presented and discussed in the light of the existing theories of bunch formation. Finally, observations of dish)cation hollow cores and decoration of growth steps on the as-grown surfaces of crystals during their extraction from supersaturated solutio~ through an ilnmiscibte solvent layer placed above the solution are described.
Journal of Crystal Growth, 1990
X-ray topographic studies of growth sector geometry in {110) sections of large potash alum crystals confirm the occurrence of growth rate dispersion of the {100} growth fronts. Contrary to previous speculations that this variation arises as a consequence of the refraction of screw dislocations in and out of these sectors we show that the dispersion occurs even in the absence of this effect and despite the presence of continuously propagating edge dislocations in the sectors. Strain mapping using double crystal diffractometry yields a strong correlation between increase of lattice strain along the sector and cessation of growth. This leads to the speculation that the potential cause of the growth rate dispersion is the absorption of undetectable amounts of impurities at the growth interface to generate the observed strain which in turn influences the growth rate (or vice versa). This speculation is in agreement with other observations of the influence of lattice strain on crystal growth.
Faceting and growth kinetics of crystals
Physica B: Condensed Matter, 2003
We review and discuss our recent results on faceting and growth kinetics of 3 He crystals imaged with a Fabry-P! erot multiple-beam interferometer at our lowest temperature of 0:55 mK: More than ten different types of facets were identified on the growing crystals and the growth rates of the individual facets were measured. Some further possible experiments are also suggested. r
The Modeling of growth process on the surface of crystal
Physics and Chemistry of Solid State
The article is devoted to modelling the growth of thin films on the surfaces of crystals having a similar crystal structure with a small parameter of mismatch of the lattice of substances from which the film and the crystal substrate are formed. A review of modelling methods based on both analytical expressions and computational methods is made. A number of methods for modelling the most typical processes: surface formation in the form of pyramidal formations (so-called needle crystals), two-dimensional with initial islands of growth and three-dimensional uneven growth processes. To model the process of growth of needle crystals, it is proposed to use a method based on Gaussian statistics of surface height increments. The model of three-dimensional growth of the crystal surface, which uses the iterative algorithm of Foss, and which makes it possible to investigate the processes of stepped, uneven growth of crystals, is also considered. In contrast to stepwise growth, a model of subm...
Growth and properties of shaped crystals
Journal of Crystal Growth, 1987
The paper summarizes the results of some shaped crystal growth research being carried out at the Ioffe Physico-Technical Institute in Leningrad and at some other institutions in the USSR, which were presented at the Stepanov Conference in Leningrad in 1985. The properties of shaped crystals and new versions of the Stepanov method are discussed.
Solution of the growth equation for asymmetric crystal faces
Polymer, 2006
Most melt-grown and many solution-grown lamellar polymer crystals have curved lateral faces. Mathematical treatments by Mansfield, Point and Villers, and Toda, have provided a satisfactory interpretation of the shape of such crystal faces in terms of nucleation and relatively slow propagation rates of layers of attaching stems. The treatments by these authors, which start with the Frank-Seto growth model, assume that the propagation rates of growth steps to the right (v r) and to the left of the secondary nucleus (v l) are equal. However, for many crystal growth faces this is not the case; faces which lack a mirror plane perpendicular to the lamella have v r sv l , resulting in asymmetric curvature. Here, we set up and solve the differential equations and reconstruct the shape of the growth front for the case of asymmetric spreading of steps. The solution is presented for the simple square lattice model. The asymmetric growth front is still described as part of an ellipse, as in the symmetric case, except that the centre of the ellipse is translated parallel to the underlying crystallographic plane in the direction of fast v. In forthcoming publications we will adapt the solution to other 2D Bravais lattices, appropriate to the crystal structures of specific polymers. Thus we will analyze complete habits of polymers such as polyethylene, poly(ethylene oxide), and poly(vinylidene fluoride), whose {110}, {120} and {110} growth faces, respectively, are asymmetric. The results of the present work allow a detail kinetic analysis of any well-developed polymer growth face in terms of the step initiation rate i and the propagation rates v r and v l. The present work also quantifies explicitly the deviations from elliptic shape and the substrate edge effects, and discusses when these can be ignored.
Crystal growth mechanisms: Interface kinetics
Materials Chemistry, 1979
A survey is given of the main theories on the interfacial kinetics of the growth from vapour and solution. Apart from the classical theory of the growth of singular faces by the 2D nucleation mechanism (mononuclear and polynuclear), special stress is laid on the fundamental of the theory of Burton, Cabrera and Frank for both the surface and volume diffusion; its more significant developments are considered as well (Chernov model on the volume diffusion, Gilmer, Ghez and Cabrera analysis of combined surface and volume diffusion processes). Furthermore the analysis of the implications of the Miiller-Krumbhaar generalized equation for crystal growth is carried out, when applied to the growth of spirals under an anisotropic chemical potential
A general mechanism of polycrystalline growth
Nature Materials, 2004
nature materials | VOL 3 | SEPTEMBER 2004 | www.nature.com/naturematerials 645 M any everyday materials, ranging from plastic grocery bags to airplane wings and cast-iron supporting beams for highway bridges, are fabricated by freezing liquids into polycrystalline solid structures. The properties and failure characteristics of these materials depend strongly on their microstructure, but the factors that determine this microstructure remain poorly understood 1 .