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Start date: 2020 × DDC: 530 × Subject: crystal growth × WGL Institute: IKZ ×

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    Czochralski growth of mixed cubic sesquioxide crystals in the ternary system Lu2O3-Sc2O3-Y2O3
    (Oxford [u.a.] : Wiley-Blackwell, 2021) Kränkel, Christian; Uvarova, Anastasia; Haurat, Émile; Hülshoff, Lena; Brützam, Mario; Guguschev, Christo; Kalusniaka, Sascha; Klimm, Detlef
    Cubic rare-earth sesquioxide crystals are strongly demanded host materials for high power lasers, but due to their high melting points investigations on their thermodynamics and the growth of large-size crystals of high optical quality remain a challenge. Detailed thermal investigations of the ternary system Lu2O3-Sc2O3-Y2O3 revealing a large range of compositions with melting temperatures below 2200°C and a minimum of 2053°C for the composition (Sc0.45Y0.55)2O3 are presented. These reduced temperatures enable for the first time the growth of high optical quality mixed sesquioxide crystals with disordered structure by the conventional Czochralski method from iridium crucibles. An (Er0.07Sc0.50Y0.43)2O3 crystal is successfully grown and characterized with respect to its crystallographic properties as well as its composition, thermal conductivity and optical absorption in the 1μm range. © 2021 International Union of Crystallography. All rights reserved.
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    Control of phase formation of (AlxGa1 - X)2O3thin films on c-plane Al2O3
    (Bristol : IOP Publ., 2020) Hassa, Anna; Wouters, Charlotte; Kneiß, Max; Splith, Daniel; Sturm, Chris; von Wenckstern, Holger; Albrecht, Martin; Lorenz, Michael; Grundmann, Marius
    In this paper, the growth of orthorhombic and monoclinic (Al x Ga1 - x )2O3 thin films on (00.1) Al2O3 by tin-assisted pulsed laser deposition is investigated as a function of oxygen pressure p(O2) and substrate temperature Tg. For certain growth conditions, defined by Tg = 580°C and p(O2) = 0.016 mbar, the orthorhombic ?-polymorph is stabilized. For Tg = 540°C and p(O2) = 0.016 mbar, the ?-, and the ß-, as well as the spinel ?-polymorph coexist, as illustrated by XRD 2?-?-scans. Further employed growth parameters result in thin films with a monoclinic ß-gallia structure. For all polymorphs, p(O2) and Tg affect the formation and desorption of volatile suboxides, and thereby the growth rate and the cation composition. For example, low oxygen pressures lead to low growth rates and enhanced Al incorporation. This facilitates the structural engineering of polymorphic, ternary (Al,Ga)2O3 via selection of the relevant process parameters. Transmission electron microscopy (TEM) studies of a ? - (Al0.13Ga0.87)2O3 thin film reveal a more complex picture compared to that derived from x-ray diffraction measurements. Furthermore, this study presents the possibility of controlling the phase formation, as well as the Al-content, of thin films based on the choice of their growth conditions. © 2020 The Author(s). Published by IOP Publishing Ltd.