Interface control of bulk ferroelectric polarization

Abstract

The control of material interfaces at the atomic level has led to novel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we employ a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectric hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite underlayers extends the generality of this phenomenon.complex oxide | heterostructure | interface physics | electronic reconstruction | polar discontinuity O ver the past few years, precisely constructed, atomically sharp perovskite oxide heterointerfaces have become focal points for condensed-matter-physics and materials science research (1-5). The incorporation and reconstruction of spin (6, 7), charge (8-10), and orbital (11) degrees of freedom across the heterointerfaces have led to novel electronic properties that are different from those inherent to the individual components. For example, pioneering work on the LaAlO 3 and SrTiO 3 (STO) heterostructures has revealed a nontrivial two-dimensional electron gas (2DEG) (10,12,13) at the interface, which also exhibits magnetic (14) and even superconductivity properties (15) that are induced by the polar discontinuity (16) (valence mismatch) across the interface.Motivated by this, research nowadays is primarily focused on probing and understanding the novel interfacial phenomena observed in complex-oxide heterostructures. However, the focus on interfacial properties sidesteps possible macroscopic implications of the interfacial atomic-scale control on the broad range of properties that are present in bulk complex oxides. On the other hand, in the semiconductor industry, atomic-scale interface engineering has long been used to improve the performance of devices through control of the threshold voltage (17), channel carrier mobility (18), Schottky barrier height (19), and so on. This forms the fundamental premise for this work: Can we control the bulk properties of a heterostructured system through the emergent state of matter at the interface? Such an approach could be particularly intriguing if one of the layers is highly polar and electrically switchable, i.e., ferroelectric in nature. Because functional ferroelectric systems, such as the nonvolatile memory (20), ferroelectric field effect transistor (21, 22), ferroelectric tunnel junction (23-27), and switching photo-diode (28), are strongly correlated with the interface electronic structures, it is of great importance to study how the interface atom...

Functional ferroic heterostructures with tunable integral symmetry

“…We note, however, that the negative bias of the local PFM loop in Fig. 2g indicates an influence on the PZT-switching behaviour exerted by the electrostatic environment or by interfacial strain 14,15 . This crosstalk suggests that the induced change of the integral symmetry may also be used to control the properties of the interlayer itself, for example, by activating spin-orbit coupling phenomena such as spin-band splitting (Rashba effect [16][17][18] ) or spin canting (Dzyaloshinskii-Moriya interaction 19 .).…”

“…Thus, the use of BFO as control layer constituent allows, for example, to exploit the electronic and the spin degrees of freedom for tuning the trilayer symmetry. BFO/LSMO/BFO trilayers were grown on (001)-oriented STO substrates leading to four ferroelectric (multiferroic) in-plane variants with P||/111S resulting from the cubic symmetry of the substrate 14,22 . The four variants are visible in Fig.…”

Theoretical Investigation of the Interfaces and Mechanisms of Induced Spin Polarization of 1D Narrow Zigzag Graphene- and h-BN Nanoribbons on a SrO-Terminated LSMO(001) Surface

“…The SrO-terminated LSMO thin film was developed as a limiting case of LSMO(001) surface following a number of experimental and theoretical publications. [70][71][72] The LSMO (001) The binding energies of 2-ZGNR, 4-ZGNR, pentacene and 4-ZBNNR with LSMO(001) substrate were calculated using the equation…”

Interface-mediated ferroelectric patterning and Mn valency in nano-structured PbTiO3/La0.7Sr0.3MnO3

“…Asymmetric space charge at the upper or lower interface of a thin film will directly favor one polarization state over the other via the built-in electric field. 10,11 The origin of the space charge can be manifold, for example, trapped charges due to the presence of ferroelectrically dead layers at the interfaces, 12,13 charge-transfer [14][15][16] dipole moments at electrically asymmetric interfaces, 17,18 or migration of charged defects inside the layer by internal or external electric fields. 1,2 As an example for interface chemistry, different imprint states occur for as-grown PbZr 0.2 Ti 0.8 O 3 (PZT) deposited on either SrRuO 3 (outward, P þ ) or La 0.7 Sr 0.3 MnO 3 (inward, P À ).…”