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the Kristallomorfologichesky analysis and indexation of facets of the monocrystals which have been grown up in a direction [110]

On buljah, extended in a direction [001], detection of unknown facets is impossible basically as their exits on a crystal surface will be always disguised by exits of four large singular facets {110}.

On lateral surfaces bul, extended in usually used direction [BUT], exits of two facets (110) and (110) are always observed, and
Also located under measured with the help goniometrov corners ±41044, to an axis [¶10 four exits of facets {101}. Correctness of indexation of these four facets proves to be true simple crystallographic calculation, according to which normal line projection to a plane (101) on

g - 1 W at

The plane (ON) should make with a direction [110] corner φ = arctg------41o44, where and = 4,796 πc = 7,626 And - critical parametres of an unit cell paratelpurita. At the inferior end face of a cylindrical part buli which surface reflects the shape of front of crystallisation at a separation from a melt flat exits of a facet (ЇЇ 0) - that major in the sizes, than less curvature of a surface, as a rule, are observed. Exits of two facets with unknown coefficients on a lateral surface should be observed under corners 90 ° to exits of facets (IlO) and (1Ї0). However on lateral surfaces of crystals paratellurita the usual shape, having the conical part dilated from a seeding agent transferring in a cylindrical part at an exit for constant peak diameter, any macroscopical morphological features of a relief reminding edges or facets are never found out.

In our operation earlier not explored facets have been found out on rather small monocrystal paratellurita, grown up by an expedient Chohralsky and 54 mm having the peak diameter and height of 72 mm as is shown in drawing 4.17. A black point - in 2 mm from the largest site of a facet.

Drawing 4.17 — the Monocrystal paratellurita with exits of unknown facets {hkl}

On the inferior, narrowed part gained buli two visually were appreciable interrupted, narrow (no more than 1 mm), symmetrically located concerning an axis vytjagivanija, a perpendicular plane (110), a path from brilliant sites the surfaces presented in drawing 4.18.

Drawing 4.18 - Exits of facets (110}, {101} and earlier not observed facets (Jikl) on the inferior conical surface of a monocrystal paratellurita

The projection of these paths to planes, a perpendicular axis buli [110] made 90 ° with a direction [001] that testified to equality of first two coefficients at the found out facets. The micromorphology of facets was studied by means of electronic raster-type microscope JEOL JSM6010LV
At various magnifications. In drawing 4.19 it is presented with magnification? 50 image of the largest, developed site of an unknown facet (hk Γ).

Drawing 4.19 Image of one of exits of facets (hkl∖полученное by means of an electronic raster-type microscope

It is well visible, that ring salients and troughs on the lateral surface, the temperatures formed owing to oscillations on interphasic boundary at vytjagivanii a crystal, on a flat site of an exit of a facet practically miss, that confirms the 3d-image of a facet gained on NanoMap according to drawing 4.20.

Drawing 4.20 - З-d the facet image (hkl)

Paths of facets (110} and (101) which are always shown on crystals, go along all crystal and have the major areas. Apparently from drawings 4, the breadth of separate flat sites of these paths is various and is spotted by growth rates of a crystal during the corresponding moments of time.

Drawing 4.21 - the Image of a long path of one of facets {101}

Drawing 4.21 - З-d the image of a facet (101)

The small sizes of the found out flat sites on a conical surface of the inferior part of a crystal did not allow to apply rentgenodifraktometricheskie methods to definition of corresponding coefficients of facets. Therefore optical methods have been used. The purpose was as more as possible exact finding of a corner which planes of facets make with an axis buli - a direction [BUT]. This corner is calculated under the formula

Where and and with - lattice parametres, h and I - crystallographic coefficients.

It is considered, that on the crystals which are grown up from a melt, morfologicheski singular facets only with rather small coefficients - in the total no more than 3-5 are shown only. And though
It is theoretically possible to pick up such major nonreducible coefficients that the corner of wasps counted according to (4.9), was as much as close to a corner found observationally, at selection of values hи Iследует to be restricted rather small in aggregate to coefficients. In table 4.2 values of a corner and depending on L coefficients, to and/, in the total not exceeding 13 are presented.

Table 4.2 - Values of a corner and, made by planes {hkl} with small coefficients with an axis [110] in crystals paratellurita

h 1 1 1 1 1 2 2 2 2 2 3 e e
1 1 2 3 4 5 1 3 5 7 9 1 2 11
And 66,1 48,4 36,9 29,4 24,2 77,5 56,3 42,0 32,7 26,6 81,6 73,5 31,5

Observationally the corner and has been certain by two expedients. It is natural to consider, that the largest, developed flat sites of a facet are in those places of a surface of a crystal where the normal line to a surface in the peak degree coincides with a normal line to a facet. Therefore the first expedient consisted that in a place of an exit of the most developed site of a facet the thin marker at observation in a binocular magnifier at magnification h 10 had been put a score. The crystal has been developed so that the facet has appeared a perpendicular plane of observation, and then is photographed by the numeral cabinet presented on drawing 4.22. Further the crystal image has been handled by computer methods, the tangent to a surface to the scored point has been constructed and the corner of wasps between a tangent and an axis buli, taking into account the method error, equal 35,8 ° is calculated.

The second expedient consisted in use of the interference profilometra NanoMap IOOOWL for a finding of sites of an exit of facets, examination of a microrelief of their surfaces, and also for definition of a corner of wasps of a declination of a facet to a base plane (Tju). Prestressly the crystal has been slited on diameter on two approximately equal parts on a plane (Tio), transiting through an axis buli. Edge surfaces on both polovinkah a crystal

doshlifovyvalis to a base plane after improvement of their orientation on X-ray diffractometer ДСО2 to within ±30 '. Further the crystal was located with the output plane (Tio) downwards on a subject little table of the interference profilometra, there were sites of an exit of studied facets according to drawing 4.23, and then on them profilogrammam the required corner and on a slope angle of a site of a surface to a base plane according to drawing 4.24 was spotted

Drawing 4.22 - Definition of a slope angle of a facet (W) to an axis [110] with the help tangent build-up to a crystal surface in a point of an exit of the greatest site of a facet

Drawing 4.23 - One of halves of crystal paratellurita with the found out facets {W}, placed by a plane (1 l θ) on a subject little table of the interference profilometra

Drawing 4.24 - profilogramma a site of a surface with a facet exit (hkl ∖

Squeezed in a horizontal direction

Measurings on various sites of an exit of facets for both halves of crystal and their processing have given value of a slope angle of facets to an axis [110] and = 35,90 °, both the first, and the second expedient of a goniometry was given by the close values. Thus in both cases these values are much closer to a corner 36,90 °, corresponding to facets {FROM}, than to the corners corresponding to other facets. In connection with the above-stated it is possible to consider fixed coefficients {113} for found out on crystals paratellurita, seldom shown and feeblly expressed in gabituse facets.

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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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  3. THE STATUS 110
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