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Start date: 2014 × Subject: GeTe ×

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    Influence of substrate dimensionality on the growth mode of epitaxial 3D-bonded GeTe thin films: From 3D to 2D growth
    (Amsterdam [u.a.] : Elsevier Science, 2019) Hilmi, Isom; Lotnyk, Andriy; Gerlach, Jürgen W.; Schumacher, Philipp; Rauschenbach, Bernd
    The pseudo-binary line of Sb2Te3-GeTe contains alloys featuring different crystalline characteristics from two-dimensionally (2D-) bonded Sb2Te3 to three-dimensionally (3D-) bonded GeTe. Here, the growth scenario of 3D-bonded GeTe is investigated by depositing epitaxial GeTe thin films on Si(111) and Sb2Te3-buffered Si(111) substrates using pulsed laser deposition (PLD). GeTe thin films were grown in trigonal structure within a temperature window for epitaxial growth of 210–270 °C on unbuffered Si(111) substrates. An unconventional growth onset was characterized by the formation of a thin amorphous GeTe layer. Nonetheless, the as-grown film is found to be crystalline. Furthermore, by employing a 2D-bonded Sb2Te3 thin film as a seeding layer on Si(111), a 2D growth of GeTe is harnessed. The epitaxial window can substantially be extended especially towards lower temperatures down to 145 °C. Additionally, the surface quality is significantly improved. The inspection of the local structure of the epitaxial films reveals the presence of a superposition of twinned domains, which is assumed to be an intrinsic feature of such thin films. This work might open a way for an improvement of an epitaxy of a 3D-bonded material on a highly-mismatched substrate (e.g. Si (111)) by employing a 2D-bonded seeding layer (e.g. Sb2Te3).
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    Epitaxial growth and characterization of GeTe and GeTe/Sb2Te3 superlattices
    (Berlin : Humboldt-Universität zu Berlin, 2017) Wang, Rui Ning
    Die epitaktische Wachstum von GeTe Dünnschichten und Sb2Te3/GeTe Übergittern durch Molekularstrahlepitaxie wird auf drei verschiedenen Silizium Oberflächen gezeigt: Si(111)−(7×7), Si(111)−(√3×√3)R30°−Sb, und Si(111)−(1×1)−H. Mit Röntgenstrukturanalyse wird bewiesen, dass die epitaktische Beziehung der GeTe Schicht von der Oberflächepassievierung abhängig ist; auf einer passivierten Fläche können verdrehte Domänen unterdrückt sein. Dieses Verhalten ähnelt dem, welches bei 2D Materialien zu erwarten wäre, und wird auf die Schwäche der Resonanten ungebundenen Zustände zurückgeführt, die durch Peierls Verzerrung noch schwächer werden.