Strain modulation of TaO4 planarity in tantalates ultrathin films: surface states engineering

Guilherme Ribeiro Portugal,Jeverson Teodoro Arantes

doi:10.1038/s41598-020-64315-7

Guilherme Ribeiro Portugal, Jeverson Teodoro Arantes

Open Access

https://doi.org/10.1038/s41598-020-64315-7

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Journal: Scientific Reports	Publication Date: May 8, 2020
Citations: 5	License type: open-access

Affiliation: Universidade Federal do ABC

Abstract

Ultrathin films of perovskites have attracted considerable attention once they fit in numerous applications. Over the years, controlling and tuning their properties have been attainable when biaxial strain is applied. Through ab initio DFT calculations, (110) ultrathin (Na,K)TaO3 films were submitted to biaxial tensile and compressive strain. Intrinsically, surface Ta shallow states emerge into the bandgap since the (110) cleavage breaks its octahedral symmetry to create TaO4 units. Removal of ligands along the x-y plane stabilizes dx2-y2 orbitals, which decrease in energy due to lower electrostatic repulsion. Such stabilization is maximized when biaxial tensile increases the TaO4 planarity towards a square planar symmetry. Accordingly, the corresponding electronic levels move further into the bandgap. Conversely, compressive biaxial strain intensifies electrostatic repulsion, closing the TaO4 tetrahedra, and surface states move to higher energy zones. The reported strain-driven modulation might be applied in different applications, as photocatalysis, ferroelectricity, and spintronics.

Highlights

Ultrathin films of perovskites have attracted considerable attention once they fit in numerous applications
ABO3 perovskite structures have been broadly studied over the last decades, mostly because they constitute a family of oxides widely found in solid-state inorganic chemistry, and because they fit into numerous technological applications[1,2,3]
The (110) cleavage in cubic KTaO3 and NaTaO3 crystals made to obtain ultrathin films modifies the Ta d orbitals degeneracy and local electrostatic interactions to such an extent that shallow surface states can be manipulated by biaxial strain

Summary

Introduction

Ultrathin films of perovskites have attracted considerable attention once they fit in numerous applications. Through ab initio density functional theory[37,38], we have systematically studied the effects of biaxial strain on (110) cubic (Na,K) TaO3 ultrathin films, emphasizing how the geometric arrangement of surface-exposed TaO4 tetrahedra influence their electronic structure.

Results

Conclusion