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Sectorial allocation of flaws of structure

One of problems of the given operation was detection and indexation of all macroscopical facets in gabituse monocrystals paratellurita, grown up by an expedient Chohralsky, and an establishment of influence of these facets on a spatial distribution of flaws of various dimensionalities in

Crystals.

As an immediate occasion to carrying out of examinations detection anywhere not mentioned facets with unknown coefficients on one of crystals has served earlier.

Besides the major sizes, from crystals paratellurita extremely high structural perfection and ideal optical homogeneity is required. Working out of new types of optical-acoustic devices (lasers, dispersion lag lines), a part super-power pulsing laser systems, and, as consequence, necessity of pinch of laser firmness of material SZP, amplification of requirements to optical homogeneity SZP of elektronno-reconstructed filters, aspiration to pinch of their spectroscopic resolution to limiting - theoretical values, - all it does actual problems of the further improvement of structural quality of crystals paratellurita and magnifications of their sizes.

At perfection of technologies of cultivation of crystals are necessary the correct and proved select of a crystallographic direction for vytjagivanija, and also the account of influence of requirements of growth on sectorial allocation of flaws in the crystals, caused various rostovoj a kinetics on the sites corresponding to singular and not singular facets. Thus, the information on all significant singular orientations of the facets sharing in formation of real structure of a crystal is important. The up-to-date state of theories of calculation of orientations of facets with the underload specific surface energies, radiating only from known data about unit cell structure, is that, that the exact prediction of singular orientations to today is represented problematic. Therefore trustier and accessible carrying out of careful crystallographic examinations of surfaces of the crystals which are grown up in various directions, with the subsequent comparison of the found out devices ogranenija with experimental data about sectorial allocation of flaws of structure in crystals by is.

Importance of definition and the account of singular facets of crystals paratellurita by working out rostovyh technologies proves to be true at least that else in operations of 70th years the optimum crystallographic direction for vytjagivanija bul from a melt [110 [114,177,186] has been empirically erected. Cultivation attempts in other, apparently, more "symmetrical" direction [001], i.e. in a direction of a symmetry axis of fourth order Z, always led to unsatisfactory effects. The crystals extended in this direction differed a high dislocation density, presence blochnosti, the raised content of gas vials, major concentrations of alien impurities, the high residual mechanical voltages often leading rastreskivaniju of crystals still in process poslerostovogo of cooling.

The most interesting effects are published in [187] and consist that the underload dislocation density is observed in volumes of the crystals adjoining two exits of facets {110} and four exits of facets {101} on lateral surfaces bul. One more direction along which the dislocation density also is small is scored. Its projection to an edge plane (ON) coincides with an axis direction Z - [00 Ї] though corresponding facets, in general, any facets on a surface bul in this direction it was never observed. Owing to orthogonality of a projection of this direction to a direction [Ї10] and ravnoudalennosti from axes Xи At, the first coefficients of a direction (and corresponding facet) should be identical - [hhl], {hh Γ). Similar allocation of dislocations in crystals paratellurita with the same binding to exterior morphology bul is featured in later operation [188] which authors applying the selective chemical etching, also have found out spotted singuljarnost in a direction of an unknown facet.

In the present operation by means of the selective chemical etching sectorial allocation of dislocations in sections of crystals paratellurita has been revealed.

In drawing to 4.15 dark sites of an edge of a crystal there corresponds a small dislocation density-Io1sm2, to light (rough) sites much higher dislocation density ~ (2-3) IO4см ’ 2. And if one of dark beams of "cross" speaks a kinetics of growth of singular facets (Ї10) and (110) orthogonal to it the beam mismatches any earlier observed in gabituse paratellurita to facets. In drawing 4.16 allocation of microvials in monocrystal section paratellurita, orthogonal [110] is shown.

Drawing 4.15 - Sectorial

Drawing 4.16-sectorial

Allocation of dislocations in

Allocation of microvials in

Monocrystal paratellurita in section, orthogonal axes vytjagivanija [110]

Monocrystal section paratellurita, orthogonal to a direction vytjagivanija [110]

4.3

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A source: Ivanova Alexandra Ivanovna. Micromorphology of a surface and dislocation structure of large-sized optical crystals of germanium and paratellurita. The dissertation on competition of a scientific degree of the candidate of physical and mathematical sciences. Tver - 2015. 2015

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