Two-dimensional Frank-van-der-Merwe growth of functional oxide and nitride thin film superlattices by pulsed laser depos
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Two-dimensional Frank–van-der-Merwe growth of functional oxide and nitride thin film superlattices by pulsed laser deposition Michael Lorenz,a) Haoming Wei, Florian Jung, Stefan Hohenberger, Holger Hochmuth, and Marius Grundmann Universität Leipzig, Felix-Bloch-Institut für Festkörperphysik, Semiconductor Physics Group, Leipzig D-04103, Germany
Christian Patzig, Susanne Selle, and Thomas Höche Fraunhofer-Institut für Mikrostruktur von Werkstoffen und Systemen IMWS, Center for Applied Microstructure Diagnostics CAM, Halle D-06120, Germany (Received 31 March 2017; accepted 16 June 2017)
Pulsed laser deposition is one of the most flexible growth methods for high-quality epitaxial multifunctional thin films and short-period superlattices. The following examples of current research interest demonstrate the state-of-the art: First, it is shown that the magnetoelectric performance of multiferroic BiFeO3–BaTiO3 (001)-oriented superlattices depends on the crystalline coherence of the different layers at the interfaces. Second, it is exemplified that dielectric-plasmonic superlattices built from the electrically insulating oxide MgO and the metallically conducting nitride TiN are promising metamaterials with hyperbolic dispersion. As a third example, it is demonstrated that LaNiO3- and LaMnO3-based superlattices with (001)-, (011)-, and (111)-out-of-plane orientation and controlled single layer thickness from 2 to 15 atomic monolayers show metal-insulator transitions and tunable gaps, in partial agreement with density functional theory calculations. Underlined by these examples, it is shown that the precise control of an epitaxially coherent, or two-dimensional layer-by-layer growth, named after Jan van der Merwe, is a prerequisite to achieve the desired functionality of oxide–oxide and oxide–nitride superlattices.
I. INTRODUCTION
Transition metal oxides and nitrides show a rich spectrum of functional properties, depending on the occupation of the respective atoms’ d-orbitals and the resulting electronic correlations.1 Thin films and superlattices built from alternating layers of two different oxides and nitrides may show novel properties based on the interaction of the two phases via interfacial strain coupling or charge exchange. Nevertheless, the synthesis and fabrication of such oxide electronic materials, as well as their transformation into demonstrator device structures is still a challenge. The recent Oxide Electronics Roadmap provides specific details directed to several fields of application.2 In contrast to well-established semiconductors, such as Si or GaAs, oxides usually suffer from a less perfect quality of single crystals and thin films.3 To date, the understanding of the role of defects in oxides is still not complete. Two-dimensional (2D) layer-by-layer growth, which is usually named Frank–van-der-Merwe growth, is Contributing Editor: Mmantsae Diale a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.266
a powerful tool to achieve abrupt interfaces and atom
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