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DDC: 530 × Subject: Growth rate ×

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    On the growth of Co-doped BaFe2As2 thin films on CaF2
    (Bristol : IOP Publ., 2019) Langer, Marco; Meyer, Sven; Ackermann, Kai; Grünewald, Lukas; Kauffmann-Weiss, Sandra; Aswartham, Saicharan; Wurmehl, Sabine; Hänisch, Jens; Holzapfel, Bernhard
    The competition between phase formation of BaF2 and Ba(Fe1-xCox)2As2 on CaF2 single crystals has been analysed. Ba(Fe0.92Co0.08)2As2 thin films have been deposited by pulsed laser deposition. X-ray diffraction, atomic force microscopy and scanning electron microscopy studies have revealed that the formation of secondary phases and misorientations as well as the growth modes of the Ba(Fe0.92Co0.08)2As2 thin films strongly depend on the growth rate. At high growth rates, formation of BaF2 is suppressed. The dependency of the Ba(Fe0.92Co0.08)2As2 lattice parameters supports the idea of fluorine diffusion into the crystal structure upon suppression of BaF2 formation similar as was proposed for FeSe1-xTex thin films on CaF2. Furthermore, a growth mode transition from a layer growth mechanism to a three-dimensional growth mode at high supersaturation has been found, suggesting similarities between the growth mechanism of iron-based superconductors and high-T c cuprate thin films. © 2019 Published under licence by IOP Publishing Ltd.
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    Epitaxial synthesis of unintentionally doped p-type SnO (001) via suboxide molecular beam epitaxy
    (Melville, NY : AIP, 2023) Egbo, Kingsley; Luna, Esperanza; Lähnemann, Jonas; Hoffmann, Georg; Trampert, Achim; Grümbel, Jona; Kluth, Elias; Feneberg, Martin; Goldhahn, Rüdiger; Bierwagen, Oliver
    By employing a mixed SnO2 + Sn source, we demonstrate suboxide molecular beam epitaxy (S-MBE) growth of phase-pure single-crystalline metastable SnO (001) thin films on Y-stabilized ZrO2 (001) substrates at a growth rate of ∼1.0 nm/min without the need for additional oxygen. These films grow epitaxially across a wide substrate temperature range from 150 to 450 °C. Hence, we present an alternative pathway to overcome the limitations of high Sn or SnO2 cell temperatures and narrow growth windows encountered in previous MBE growth of metastable SnO. In situ laser reflectometry and line-of-sight quadrupole mass spectrometry were used to investigate the rate of SnO desorption as a function of substrate temperature. While SnO ad-molecule desorption at TS = 450 °C was growth-rate limiting, the SnO films did not desorb at this temperature after growth in vacuum. The SnO (001) thin films are transparent and unintentionally p-type doped, with hole concentrations and mobilities in the range of 0.9-6.0 × 1018 cm-3 and 2.0-5.5 cm2 V-1 s-1, respectively. These p-type SnO films obtained at low substrate temperatures are promising for back-end-of-line (BEOL) compatible applications and for integration with n-type oxides in pn heterojunctions and field-effect transistors.