Summary
A detailed study of the structural modifications present in GaS and GaSe crystals has been performed by means of the convergent-beam electron diffraction technique. Several single crystals have been analysed, as grown both from the melt, by the Bridgmann-Stockbarger method, and from the vapour, by the iodine-assisted chemical transport method. The results of the electron microscopy observation show the structure of GaSe to be strongly dependent on the growth method. In the melt-grown crystals only the hexagonal β structure (space group P63/mmc) has been observed for both GaS and GaSe. It has been confirmed by the related symmetry centre, evidenced in particular low symmetry orientation of the samples. The vapour-grown crystals show the same β structure for GaS and the superposition of the hexagonal ε polytype (space group \(P\bar 62m\)) and the rhombohedral γ polytype (space group R3m) for GaSe samples. An accurate evaluation of the lattice parameters has been performed for all the analysed crystals.
Riassunto
È stato effettuato uno studio dettagliato delle modificazioni strutturali presenti in monocristalli di GaS e GaSe, utilizzando la tecnica della diffrazione elettronica a fasci convergenti. Sono stati analizzati cristalli cresciuti sia dal fuso con il metodo Bridgman-Stockbarger, sia da fase vapore per trasporto chimico assistito da iodio. I risultati delle osservazioni hanno mostrato che la struttura del GaSe dipende fortemente dal metodo di crescita, mentre questo non si verifica per il GaS. Infatti, i cristalli cresciuti dal fuso, sia di GaS che di GaSe, sono costituiti solo dal politipo esagonale β con gruppo spaziale P63/mmc, la cui presenza è stata confermata dall’osservazione del centro di simmetria caratteristico di tale struttura. I cristalli di GaS cresciuti da fase vapore sono costituiti dal politipo esagonale β, mentre queli di GaSe sono costituiti dalla sovrapposizione del politipo esagonale ε, avente gruppo spaziale \(P\bar 62m\), e dal politipo romboedrico γ con gruppo spaziale R3m.
Резюме
Проводится подробное исследовние структурных изменений в кристаллах GaS и GaSe, используя метод дифракции сходящегося электронного пучка. Проведен анализ некоторых монокристаллов, выращенных из расплава, с номощью метода Бридгмана-Стокбаргера, из паровой фазы и с помощью химического метода переноса. Результаты наблпюдений с помощью электронной микрокопии показывают, что структура GaSe сильно зависит от метода выращивания. В кристаллах, выращенных из расплава, наблюдается только гексагональная β структура для GaS и для GaSe. Кристаллы, выращенные из паровой фазы, обнаруживают β структуру для GaS и суперпозицию гексагонального ε политипа и ромбоэдрического γ политипа для образцов GaSe. Для всех рассмотренных кристаллов проведена аккуратная оценка параметров решетки.
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References
R. M. A. Lieth: Crystal Growth of Materials with Layered Structures, edited by R. M. A. Lieth (Reidel, Dordrecht, 1976), p. 225.
A. M. Mancini, G. Micocci and A. Rizzo: Mat. Chem. Phys., 9, 29 (1983).
J. W. Steeds: Introduction to Analytical Electron Microscopy, edited by J. I. Golstein and D. C. Joy (Plenum Press, New York, N.Y., and London, 1979), Chapt. 15, p. 387.
P. Goodman and H. J. Whitfield: Acta Cryst. A, 36, 219 (1980).
J. M. Cowley: Prog. Mat. Sci., 13, 267 (1967).
R. Uyeda: J. Appl. Cryst., 7, 1 (1974).
M. Tanaka, R. Saito, K. Ueno and Y. Harada: J. Electron. Microsc., 29, 408 (1980).
C. Manfredotti, A. Rizzo, A. Bufo and V. L. Cardetta: Phys. Status Solidi, 30, 375 (1975).
M. Spandau and F. Klanberg: Z. Anorg. Allgem. Chem., 295, 300 (1958).
P. Goodman and H. J. Whitfield: Acta Cryst. A, 36, 219 (1980).
B. F. Buxton, J. A. Eades, J. W. Steeds and G. M. Rackham: Philos. Trans. R. Soc. London A, 281, 171 (1976).
P. Goodman: Acta Cryst. A, 31, 804 (1975).
C. De Blasi, M. Di Giulio and D. Manno: Ultramicroscopy, 26, 377 (1988).
C. De Blasi, D. Manno and A. Rizzo: Study of the polytypism in melt grown InSe single crystals by convergent beam electron diffraction, to be published.
H. Hahn: Angew. Chem., 65, 538 (1953).
F. Jellinek and H. Hahn: Z. Naturforsch., 16, 713 (1961).
W. Schubert and E. Dorre: Naturwissenschaften, 40, 604 (1953).
W. Schubert, E. Dorre and M. Kluge: Z. Metall., 46, 216 (1955).
J. C. J. M. Terhell and R. M. A. Lieth: Phys. Status Solidi A, 5, 719 (1971).
H. Suzuki and R. Mori: Jpn. J. Appl. Phys., 13, 417 (1974).
G. Arancia, M. Grandolfo, C. Manfredotti and A. Rizzo: Phys. Status Solidi A, 33, 563 (1976).
C. R. Whitehouse and A. A. Balchin: J. Mat. Sci., 13, 2394 (1978).
Unpublished SAD measurements performed by the authors.
Unpublished X-ray measurements performed by the authors.
C. De Blasi, D. Manno, S. Mongelli and A. Rizzo: Nuovo Cimento D, 7, 795 (1986).
A. Chevy: J. Cryst. Growth, 51, 157 (1981).
A. Rizzo, C. De Blasi, M. Catalano and P. Cavaliere: Phys. Status Solidi A, 105, 101 (1988).
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De Blasi, C., Manno, D. & Rizzo, A. Convergent-beam electron diffraction study of melt-and vapour-grown single crystals of gallium chalcogenides. Nouv Cim D 11, 1145–1163 (1989). https://doi.org/10.1007/BF02459022
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DOI: https://doi.org/10.1007/BF02459022