The inversion twin: Prototype in beryllium oxide

Austerman, S.B.; Gehman, William G.

doi:10.1007/bf00550173

Cited by 64 publications

(33 citation statements)

References 34 publications

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“…The same displacement may not be found necessarily for other crystals in which impurity concentrations may change the state of lattice relaxation (Austerman & Gehman, 1966) or for crystals in which the boundaries lie in other directions than parallel to the c axis. Boundaries with other orientations can be analyzed with the theory used here.…”

Section: Resultsmentioning

confidence: 83%

“…Rather than the sharp boundary shown in Fig. 7, it is quite likely that the net displacement of the oxygen layers could take place over a distance of several unit cells on either side of the boundary, accompanied by a corresponding gradual change in statistical occupation of the two sets of tetrahedral sites by the beryllium atoms as described by Austerman & Gehman (1966). The X-ray diffraction effects are considered to be insensitive to the sharpness of the boundary transition as just described.…”

Section: [(N/2)+(1/16)]mentioning

confidence: 96%

“…It has been assumed that, in inversion twins of BeO crystals, the sublattice of oxygen atoms is continuous and straight across the twin boundary, and that the discontinuity exists only in the sublattice of the beryllium atoms Austerman & Gehman, 1966). If the oxygen layers parallel to the basal plane were straight across the boundary no contrast would be expected for 004 and 008 reflections because u = 0 and ct = 0.…”

Section: The Structure Of the Inversion Twin Boundarymentioning

confidence: 99%

“…Flux-grown BeO crystals commonly are twinned, whereby the two components of the twin have opposite senses of the polar axes. The twin structure was found in BeO crystals by Austerman (1962), and has been formally described (Blank, Delavignette, Gevers & Amelinckx, 1964;Newkirk & Smith, 1964;Austerman & Gehman, 1966) and has been designated as the 'inversion twin' (Austerman & Gehman, 1966). The wurtzite structure can be considered as a hexagonally close packed stacking of A atoms with the other B atoms in tetrahedral interstices.…”

Section: Introductionmentioning

confidence: 99%

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X-ray diffraction contrast of inversion twin boundaries in BeO crystals

Chikawa¹,

Austerman²

1968

J Appl Cryst

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Inversion twin boundaries in BeO crystals (wurtzite structure) can be studied by X-ray topography. They can be regarded as a special kind of stacking fault. The section topograph images of a twin boundary, lying parallel to the c axis, agree well with the theory for a single stacking fault. From the contrast variation of the images for various reflections, it is concluded that the oxygen sublattice on one side of the twin boundary is displaced from that on the other side by 1(1/16)[00111 so that the oxygen layer parallel to the basal plane on one side is located at the center of the oxygen and beryllium layers on the other side. The image contrast in section topographs is very sensitive to the phase shift due to a fault. The phase shift of a few degrees can be detected easily. This sensitivity leads to an accurate structure determination of the inversion twin boundary.

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Section: Resultsmentioning

confidence: 83%

Section: [(N/2)+(1/16)]mentioning

confidence: 96%

Section: The Structure Of the Inversion Twin Boundarymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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X-ray diffraction contrast of inversion twin boundaries in BeO crystals

Chikawa¹,

Austerman²

1968

J Appl Cryst

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“…One can interpret the stucture using the interstice lattice stacking fault model of Austerman and Gechman [5]. Here, the uncompensated Se and Zn ions create the panes of negative (N) and positive (P) charge [6], respectively.…”

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confidence: 99%

Influence of Twinning on Local Electronic Properties of ZnSe

1992

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We have obtained ZnSe single crystals by vertical Bridgman method. The surface was examined using scanning electron microscope (SEM). As usual crystals exhibited twins, which were observed on the (110) surface. On as-grown and n-type samples we observed long (of the order of millimetres) linear structures parallel to the (111) plane which correspond to the twin plane. Our observations and measurements enabled us to estimate the electronic potential as being of the order of a few volts and extending less than 1 μm in the direction perpendicular to the twin planes.PACS numbers: 61.70. Ng, 71.55.Gs, 72.80.Ey Twining is a common stuctural defect in the production of ZnSe crystals which extends on available (111) twin plane in the crystal [1]. Some authors predict the mechanism due to which twins may control the type and the value of material conductivity. In 1983 Fitzpatrick et al. [2] showed that macroscopic defects (including twins) may remove compensating centres in ZnSe. Wojtowicz and Malińskí [3], who investigated the polarization spectra of Ag in ZnSe, suggested that the observed polarization peaks result from the additional electric field related to the charge of the twin plane. The aim of this work is the direct observation of this field. We examined the (110) surface of ZnSe crystal (the surface perpendicular to the twin planes) using SEM and transmission electron microscope (TEM).We obtained ZnSe single crystals using vertical Bridgman method. The density of twins along [111] direction is about 300/mm. The crystals were broken along cleavage plane {110}. The resistivity of one set of the samples was reduced in molten zinc [4], the samples were kept in 1233 K for 48 hours. The resistivity of the samples received was 0.2 Ωcm. A small gold dot with sharp edges on (110) surface of some samples was evaporated. The typical view of high resistivity sample is presented in Fig. 1. This is a view of mirror like surface of (110) plane. The lines are parallel to [112] direction which is parallel to (111) plane. They form sharp lines, alternately lighter and darker than the area between them. The areas between the lines are of the same black colour. The resolution of that

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Atomic Structure of Extended Defects in Wurtzite GaN Epitaxial Layers

Ruterana

Nouet

2001

phys. stat. sol. (b)

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Using high resolution electron microscopy, atomistic modelling and image simulations, typical contrast was identified for most of the extended defects which form in epitaxial GaN layers. There are three types of defects which propagate into the active layers: the threading dislocations, prismatic stacking faults and inversion domains. The atomic structure of the a pure edge threading dislocations was shown to exhibit 5/7, or 8 atom cycles. The two configurations were observed at a similar frequency for isolated dislocations and low angle grain boundaries. Coincidence grain boundaries were studied and they were made of pure edge a dislocations with the above identified atomic structures. A topological analysis of high angle grain boundaries was carried out in order to determine the defect content at the interfaces. The reconstruction of some boundaries was only possible by taking into account the occurrence of structural units which exhibit 4 atom ring cycles for the dislocation cores. The f1 2 210g stacking fault has two atomic configurations in wurtzite (Ga, Al, In)N with 1/2 h10 1 11i and 1/6 h20 2 23i displacement vectors. It originates from steps at the SiC surface and it can form on a flat (0001) sapphire surface. The two atomic configurations have comparable energy in AlN, whereas the 1/2 h10 1 11if1 2 210g atomic configuration should be more stable in GaN and InN. Observations carried out in plan-view show the 1/2 h10 1 11if1 2 210g atomic configuration in GaN layers. The 1/6 h20 2 23i configuration was found inside the AlN buffer layer in cross section observations. It folds rapidly to the basal plane, and when back into the prismatic plane, it bears the 1/2 h10 1 11if1 2 210g atomic configuration. The f10 1 10g inversion domains in GaN layers grown on sapphire substrate were identified in multi-beam dark field images and by convergent beam electron diffraction. In the investigated samples, Holt and V models are shown to form in samples depending on the growth conditions. The samples containing Holt inversion domains exhibited a flat surface morphology, whereas the V IDBs were observed in the centre of small pyramids (100 nm high) protruding at the sample surface. The Holt inversion domains were always smaller (< 20 nm), at quite high densities (2.5 Â 10 10 cm --2 ), whereas the V ones could reach 50 nm and one order of magnitude lower density. The inversion domains were found to be generated mostly at sapphire surface steps where they minimized the large misfit along the c axis (20%).

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The inversion twin: Prototype in beryllium oxide

Cited by 64 publications

References 34 publications

X-ray diffraction contrast of inversion twin boundaries in BeO crystals

X-ray diffraction contrast of inversion twin boundaries in BeO crystals

Influence of Twinning on Local Electronic Properties of ZnSe

Atomic Structure of Extended Defects in Wurtzite GaN Epitaxial Layers

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