Design of Complex Oxide Interfaces by Oxide Molecular Beam Epitaxy

Abstract

Complex oxides provide a versatile playground for many phenomena and possible applications, for instance, high-temperature superconductivity, magnetism, ferroelectricity, metal-to-insulator transition, colossal magnetoresistance, and piezoelectricity. The origin of these phenomena is the competition between different degrees of freedom such as charge, orbital, and spin, which are interrelated with the crystal structure, the oxygen stoichiometry, and the doping dependence. Recent developments not only in the epitaxial growth technologies, such as reactive molecular beam epitaxy, but also in the characterization techniques, as aberration-corrected scanning transmission electron microscopy with spectroscopic tools, allow synthesizing and identifying epitaxial systems at the atomic scale. Combination of different oxide layers opens access to interface physics and leads to engineering interface properties, where the degrees of freedom can be artificially modified. In this review, we present different homo-and hetero-epitaxial interfaces with extraordinary structural quality and different functionalities, including hightemperature superconductivity, thermoelectricity, and magnetism.

Probing surfaces and interfaces in complex oxide films via in situ X-ray photoelectron spectroscopy

“…Advances in thin film synthesis continue to drive the field as well. New approaches to molecular beam epitaxy (MBE) [9,10,11] and pulsed laser deposition (PLD) [12,13] enable more precise control of cation stoichiometry than previously possible. Such approaches are highly complementary with materials characterization techniques that help to explain the physical origins of emergent phenomena in oxide thin films and interfaces.…”

Probing surfaces and interfaces in complex oxide films via in situ X-ray photoelectron spectroscopy

“…Advances in thin film synthesis continue to drive the field as well. New approaches to molecular beam epitaxy (MBE) [9,10,11] and pulsed laser deposition (PLD) [12,13] enable cambridge.org/JMR 1 more precise control of cation stoichiometry than previously possible. Such approaches are highly complementary with materials characterization techniques that help to explain the physical origins of emergent phenomena in oxide thin films and interfaces.…”

Precise control of atoms with MBE: from semiconductors to complex oxides

“…The selective AL deposition (with one AL at a time) and the precise control of the concentration of the impurities paves the way for designing functional heterostructures to engineer novel metastable compounds; (iv) the lowest energy of impinging atoms: Different than other physical deposition methods MBE has the lowest energy of impinging atoms (<0.1eV) providing the lowest undesirable cation intermixing at the interfaces. These superiorities allow versatile heterostructural design with a controlled thickness down to a single sheet of atoms resulting in abrupt heterointerfaces [6]. These heterostructures are the building blocks of different kinds of diodes, transistors, including solar cells as well as microprocessors and memory devices.…”

“…The layered crystal structure of TM oxide compounds are generally represented by Ruddlesden-Popper (RP) phases with A n+1 B n O 3n+1 formula, where A represents alkali, alkaline earth, or rare earth metal, B is the TM, and n -integer number. These RP phases consist of two-dimensional perovskite-like slabs (Figure 2a) that can be precisely designed by MBE [6]. The AL-by-AL method is best suited for the fabrication layered oxides, where the precise counting of the constituent atoms is realized via shuttering.…”

“…The prominent role is played by aberration-corrected scanning transition electron microscopy (STEM) with high-resolution imaging and spectroscopy capabilities [14,15]. STEM high-angle annular dark field (HAADF) images of three different La 2 CuO 4 -based heterostructures are presented in Figure 3a-c [6] displaying the ideally arranged crystal structure without any extended defects.…”