Atomic-Scale Insights on Large-Misfit Heterointerfaces in LSMO/MgO/c-Al2O3

Soumya Mandal,Ashish Kumar Gupta,Ritesh Sachan,Jagdish Narayan,Braxton Hays Beavers,Vidit Singh

doi:10.3390/cryst11121493

Soumya Mandal, Ashish Kumar Gupta + Show 4 more

Open Access

https://doi.org/10.3390/cryst11121493

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Abstract

Understanding the interfaces in heterostructures at an atomic scale is crucial in enabling the possibility to manipulate underlying functional properties in correlated materials. This work presents a detailed study on the atomic structures of heterogeneous interfaces in La0.7Sr0.3MnO3 (LSMO) film grown epitaxially on c-Al2O3 (0001) with a buffer layer of MgO. Using aberration-corrected scanning transmission electron microscopy, we detected nucleation of periodic misfit dislocations at the interfaces of the large misfit systems of LSMO/MgO and MgO/c-Al2O3 following the domain matching epitaxy paradigm. It was experimentally observed that the dislocations terminate with 4/5 lattice planes at the LSMO/MgO interface and with 12/13 lattice planes at the MgO/c-Al2O3 interface. This is consistent with theoretical predictions. Using the atomic-resolution image data analysis approach to generate atomic bond length maps, we investigated the atomic displacement in the LSMO/MgO and MgO/c-Al2O3 systems. Minimal presence of residual strain was shown at the respective interface due to strain relaxation following misfit dislocation formation. Further, based on electron energy-loss spectroscopy analysis, we confirmed an interfacial interdiffusion within two monolayers at both LSMO/MgO and MgO/c-Al2O3 interfaces. In essence, misfit dislocation configurations of the LSMO/MgO/c-Al2O3 system have been thoroughly investigated to understand atomic-scale insights on atomic structure and interfacial chemistry in these large misfit systems.

Highlights

The nature of epitaxial growth and the control of defects in the thin film heterostructure are considered of significant importance for tuning next-generation electrical, optical, and magnetic devices [1,2]
LSMO is typically grown on SrTiO3 (STO) or MgO, the lattice misfit differs between LSMO/MgO and LSMO/STO
Complete film relaxation can be achieved within a few monolayers, allowing the subsequent film to grow relaxed or strain free. This process can be explained by domain-matching epitaxy (DME), where integral multiples of lattice constants match across film–substrate interfaces [17,18]

Summary

Introduction

The nature of epitaxial growth and the control of defects in the thin film heterostructure are considered of significant importance for tuning next-generation electrical, optical, and magnetic devices [1,2]. It is well established that the misfit present at the interface introduces strain in the system and is gradually relieved after a few hundred monolayers This result ensures the thin film properties are directly influenced by the interfacial defects. Complete film relaxation can be achieved within a few monolayers, allowing the subsequent film to grow relaxed or strain free This process can be explained by domain-matching epitaxy (DME), where integral multiples of lattice constants match across film–substrate interfaces [17,18]. A detailed investigation of the interfacial structure was performed on the oxide heterostructure LSMO/MgO/cAl2O3 utilizing aberration-corrected scanning transmission electron microscopy (STEM) together with electron energy-loss spectroscopy (EELS) measurements. This study signifies the importance of misfit dislocations in thin film, representing a promising pathway in the improvement of film quality and its associated properties

Experimental Methodology

Conclusions