Use of lattice imaging in the electron microscope in the structure determination of the 126<i>R</i>polytype of SiC

Dubey, Madan; Singh, G.

doi:10.1107/s0567739478000200

Cited by 14 publications

(9 citation statements)

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“…Verma & Krishna, 1966) but is not suitable for the study of more complicated sequences, or when finescale structural variations such as stacking faults occur. Electron diffraction and electron microscopy have also been applied to the structure determination of long-period polytypes (Sato, Shinozaki & Yessik, 1974;Yessik, Shinozaki & Sato, 1975;Dubey & Singh, 1978). However, because of limited resolution, identification of detailed stacking sequences within the longperiod structures necessitated trial structure factor calculations based on the small number of possible variants.…”

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confidence: 99%

The direct identification of stacking sequences in silicon carbide polytypes by high-resolution electron microscopy

Jepps¹,

Smith²,

Page³

1979

Acta Cryst Sect A

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916LE FLUOSILICATE DE MAGNESIUM types de domaines ordonn6s, de grande extension, 6quirepr6sent6s dans le cristal. Un type de domaine contient, pour chaque vari&6 d'anions, deux orientations A pour une orientation B, l'autre deux orientations B pour une orientation A. I1 est remarquable qu'une analyse structurale classique des compos6s NiSiF 6. 6H20 et ZnSiF 6. 6H20 (Ray, Zalkin & Templeton, 1973) ait conduit ~t des proportions identiques pour les deux orientations d'octa6dres (deux orientations A pour une orientation B), dans le cas d'une r6partition d6sordonn6e de ces octa6dres (R3). La structure pr6sent6e (P3) pour MgSiF 6. 6H20 peut ~tre regard6e comme une structure antiphas6e p6riodique, b. p6riode enti~re [2M = 3d(101)], fond6e sur la structure ordonn6e monoclinique de basse temp&ature (P21/c).Cette mani~re d'envisager la structure du fluosilicate de magn6sium devait nous permettre de traiter le cas du fluosilicate de fer dans toutes ses particularit~s (taches de surstructure d'extension variable h indices non strictement entiers). Cette &ude en voie d'ach~vement fera l'object d'une prochaine publication.Nous remercions R. Saint-James pour la pr6paration d'6chantillons, A. Hardy pour sa collaboration h la mesure des intensit+s diffract6es et P. P&io avec qui nous avons eu des fructueuses discussions. Acta Cryst. (1979 AbstractLattice imaging with tilted illumination at the 2.5 A level has been used for the direct determination of stacking sequences in silicon carbide polytypes by observation of electron micrographs. The method employed is first demonstrated by observations of the common short-period polytypes 3C, 4H, 15R and 6H, and is then used to reveal the stacking sequences in the polytypes 9R and 129R, neither of which appear to have been reported previously. Stacking sequences in 0567-7394/79/060916-08501.00 disordered and faulted materials have also been characterised.

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The direct identification of stacking sequences in silicon carbide polytypes by high-resolution electron microscopy

Jepps¹,

Smith²,

Page³

1979

Acta Cryst Sect A

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“…Therefore, series-truncation errors are comparatively less, making fringe separations less sensitive to foilthickness variations at an appropriate defocus value. Thus, structural information available from onedimensional fringes contains less details but is more reliable (Dubey & Singh, 1978;Singh & Singh, 1980;Singh et al, 1981;Yessik et al, 1975;Ogbuji et al, 1981 ;Kuo et al, 1982). Therefore, wherever possible, a combination of linear fringe spacings and chevronshaped fringes should be utilized to derive the structural information.…”

Section: Discussionmentioning

confidence: 99%

“…The utility of low-resolution lattice images has already been established in the structural investigations of SiC structures of large cell parameters (Dubey & Singh, 1978;Singh & Singh, 1980;Singh, Singh & Van Tendeloo, 1981;Yessik, Shinozaki & Sato, 1975;Ogbuji, Mitchell & Heuer, 1981;Kuo, Zhou, Ye & Kuo, 1982). It has been suggested by Jepps, Smith & Page (1979) that tiltedbeam two-dimensional lattice images are capable of directly revealing the stacking sequence in SiC polytype structures.…”

Section: Introductionmentioning

confidence: 99%

High-resolution electron microscopic studies on a new polytype of SiC and its intergrowth structures

S.¹,

Korgul²,

Singh³

1984

Acta Crystallogr Sect B

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Tilted-beam two-dimensional lattice images have been used to determine the structure of a new polytype of SiC, viz 411 R, and its intergrowth structures.Initially, the chevron-shaped fringes in a simple structure of 6H were obtained and analysed with the help of computer simulation based on the multislice approach of Cowley & Moodie [Acta Cryst. (1957), 10, 609-619] in order to arrive at optimum experimental conditions. The method was then applied to a high-period polytype 411R and its intergrowth structures. The suitability of this technique for structural investigations is discussed.

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“…(ii) Powdering or crushing of Sic (Dubey et al, 1977; Dubey & Singh, 1978) or ZnS crystals (Fleet, 1975).…”

Section: Introductionmentioning

confidence: 99%

“…(iv) Evaporation and recrystallization under the electron beam, as used by Gasgnier et al (1976) on Dy Al3 thin films or Dubey & Singh (1974) on Sic.…”

Section: Introductionmentioning

confidence: 99%

Using RHEED to study polytypism

Gauthier

1980

Journal of Microscopy

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Up to now, relatively few papers have dealt with electron beam investigations of polytypic substances. Recent work in Sic (Gauthier, 1978) pointed out the general interest in the use of reflection high energy electron diffraction (RHEED) for examining well-ordered long-period mod8ications. The main results are summarized here, showing what information can be obtained from RHEED patterns for the determination of polytype structures and hence possible explanations of growth mechanisms. In the same way, other materials have now been examined by the same technique and some results from zinc sulphide crystals are presented as an illustration. The mixtures of different ZnS modifications are complex; moreover, polytype disorder exists commonly in that substance. Such a situation vindicates the use of other techniques, particularly high resolution electron microscopy.

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Use of lattice imaging in the electron microscope in the structure determination of the 126Rpolytype of SiC

Cited by 14 publications

References 3 publications

The direct identification of stacking sequences in silicon carbide polytypes by high-resolution electron microscopy

The direct identification of stacking sequences in silicon carbide polytypes by high-resolution electron microscopy

High-resolution electron microscopic studies on a new polytype of SiC and its intergrowth structures

Using RHEED to study polytypism

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