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Title

Gas phase synthesis of epitaxial layers of nickel-chlorine boracite on chromium-chlorine boracite

Authors
Tippmann, Heinz
Published in Journal of Crystal Growth. 1979, vol. 46, no. 6, p. 723-742
Abstract Layers of Ni boracite were epitaxially grown on Cr-Cl boracite at 900 Deg. At the reaction temperature both substrate and layer had the cubic 43m symmetry whereas at room temperature the layer is ferroelectric (symmetry mm2) and the substrate is still cubic. The layers were produced both by (1) CVT reactions in closed quartz ampules and by 2 variants of a CVD process by using either the reactants BCl3(g) + H2O(g), or B2O3(g) for the formation of the intermediate gaseous (BOCl)3 and the B2O3 hydrates. The reactant NiCl2(g) was obtained by reaction Ni(s) + Cl2(g) = NiCl2(g) at .apprx.1000 Deg inside the reactor. Layer thicknesses of 1-100 mm were achieved. The growth rate was .apprx.1 mm/min. The best substrates were those with smooth, as-grown surfaces; these layers were characterized after cooldown by a pattern of ferroelectric 180 Deg domains with the spontaneous polarization oriented perpendicularly to the surface, an average domain size of 1-10 mm and good contrast (at l = 546 nm) between antiparallel domains placed between crossed polarizers and a retarder. The ferroelectric poling fields were >107 V/m.
Keywords Epitaxy nickel boracite chromium boraciteFerroelectric nickel boracite
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SCHMID, Hans, TIPPMANN, Heinz. Gas phase synthesis of epitaxial layers of nickel-chlorine boracite on chromium-chlorine boracite. In: Journal of Crystal Growth, 1979, vol. 46, n° 6, p. 723-742. https://archive-ouverte.unige.ch/unige:33303

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Deposited on : 2014-01-16

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