Regensburg 2025 – scientific programme

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DS: Fachverband Dünne Schichten

DS 2: Layer Deposition

DS 2.1: Talk

Monday, March 17, 2025, 09:30–09:45, H14

Bidirectional Growth of Functional Oxides by Molecular Beam Epitaxy — •Nicolas Bonmassar¹, Georg Christiani², and Gennady Logvenov² — ¹University of Stuttgart, 70569 Stuttgart, Germany — ²Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany

Here I present some recent results on the use of offcut substrates by enabling atomic precision layer-by-layer growth in both in-plane and out-of-plane directions. This is achieved by in situ monitoring of the oscillations of the reflected high-energy electron diffraction (RHEED) patterns. The potential of this method is demonstrated using a bidirectionally grown superlattice of alternating LaMnO₃ and SrMnO₃ layers, showing interfacial ferromagnetism. This superlattice serves as a model system to showcase the method’s versatility through detailed structural and functional characterization by using various scanning transmission electron microscopy techniques, sheet resistance measurements, and magnetometry. Next, the approach is applied to the growth of superconducting La_1.84Sr_0.16CuO₄ thin films grown in ozone atmosphere on various offcut substrates, where the anisotropic critical current is found to arise from two distinct mechanisms induced by the substrate geometry.

Furthermore, I will present the issues we faced when we first started this project and how we had overcome well-known problems like the loss over the in situ RHEED oscillations, terrace broadening, step bunching, 3D defect formation and the concomitant loss of functionalities like superconductivity.

Keywords: In situ RHEED; Ozone; Molecular Beam Epitaxy; Scanning Transmission Electron Microscopy; Functional Oxides