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Journal Article | FZJ-2020-02400 |
; ;
2020
IOP Publ.87703
Bristol
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Please use a persistent id in citations: http://hdl.handle.net/2128/25147 doi:10.1088/1742-6596/1559/1/012011
Abstract: Atomic-scale imaging of interfacial polarizationin cuprate-titanate heterostructuresCite as: Appl. Phys. Lett. 116, 251603 (2020); doi: 10.1063/5.0011081Submitted: 17 April 2020 . Accepted: 7 June 2020 .Published Online: 23 June 2020Shao-Bo Mi,1,a) Tian Yao,1 Shao-Dong Cheng,1,2 Micheal I. Faley,3 Ulrich Poppe,3 Lu Lu,1,2 Dawei Wang,1,2and Chun-Lin Jia1,2,3AFFILIATIONS1State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China2School of Microelectronics, Xi’an Jiaotong University, Xi’an 710049, China3Ernst Ruska Centre for Microscopy and Spectroscopy with Electrons and Peter Gr€unberg Institute,ForschungszentrumJ€ulich, D-52425 J€ulich, Germanya)Author to whom correspondence should be addressed: shaobo.mi@xjtu.edu.cnABSTRACTThe interfaces in oxide heterostructures that bring novel physical phenomena and functionalities have attracted great attention infundamental research and device applications. For uncovering structure–property relationships of oxide heterostructures, direct evidence ofthe atomic-scale structure of heterointerfaces is highly desired. Here, we report on studying the structure of interfaces between YBa2Cu3O7-dthin films and SrTiO3 substrates by means of aberration-corrected ultrahigh-resolution electron microscopy. Employing advanced imagingand spectroscopic techniques, shifts of atoms at the interface away from the regular lattice sites are measured, leading to the interfacial polarity.The local polarization induced by the atomic shifts directs toward the cuprate films and is estimated to be about 36.1 lC/cm2. Theobserved interfacial polar layer is understood by the special atomic configuration across the interface, which could modulate the electricalproperties in superconducting devices that are based on the ferroelectric/superconductor heterosystems.Published under license by AIP Publishing. https://doi.org/10.1063/5.0011081Heterostructures of perovskite-based oxide materials haveattracted extensive attention from both fundamental research andtechnological applications because of their variety of fascinating physicalproperties.1,2 It has been demonstrated that interfaces in thedesigned heterostructures have striking properties, which do not existin either of the constituent bulk materials, e.g., 2D electron gas at theLaAlO3/SrTiO3 (LAO/STO) interface.3,4 In addition, the functionalitiesof the perovskite-based oxide epitaxial layers can be modulated bythe field effect arising from the adjacent layers or/and the interfacecoupling in heterostructures (e.g., proximity effects in superconductor–ferromagnet heterostructures).5–7 Among the perovskite-basedheterostructures, strongly electron-correlated materials are of essentialimportance due to their applications in superconducting field-effectdevices, e.g., high-temperature superconducting (HTS) ultrathin filmsgrown on insulating STO substrates.8–10 In these heterostructures, thecritical temperature (Tc) and phase transitions of the HTS cupratefilms can be tuned by an external electric field without involvingchemical and crystalline modulation of the materials. Also, it wasreported that the Tc of the ultrathin HTS films can be shifted by thecharge carriers, which are injected by the dielectric gate polarizationunder an applied electric field and thus leading to a suppression ofsuperconductivity in the ultrathin HTS films.11–14The Thomas–Fermi screening length (kTF) of YBa2Cu3O7-d(YBCO) is on the order of 1nm.15 Therefore, the interface couplingbetween the dielectric gate and the YBCO films has importanteffect on shifting Tc of the ultrathin YBCO films. In particular, theinterfacial polarity of the heterostructures has been expected tochange the doping level and thus to affect the superconductivity ofthe unit-cell-thick HTS cuprate films.16 Although the experimentaland theoretical investigations have been performed on studyingHTS heterostructures,9,10,17–19 the interfacial atomic arrangementof superconducting/insulating heterostructures, including reconstructions,relaxations, interatomic mixing, and distortions, is necessaryto be clarified for a deep insight into the mechanismsbehind the experimentally measured interface-related properties.In this work, we provide the atomic-scale interface structure ofYBCO/STO(001) obtained by using high-resolution imaging andspectroscopic techniques of aberration-corrected transmissionelectron microscopy (TEM) and scanning transmission electronmicroscopy (STEM).Appl. Phys. Lett. 116, 251603 (2020); doi: 10.1063/5.0011081 116, 251603-1Published under license by AIP PublishingApplied Physics Letters ARTICLE scitation.org/journal/apl
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