Correlating polar distortions and interfacial charge at the polar/non-polar LaCrO3/SrTiO3 (001) interface

A H Al-Tawhid,D P Kumah

doi:10.1063/5.0002298

Abstract

The relationship between the sheet carrier concentration, ns, of LaCrO3(LCO)/SrTiO3(STO) heterostructures and their structural properties has been investigated. Under low oxygen partial pressure, the STO substrate is reduced during growth as evidenced by a high ns of 1016 cm−2. By controlling the post-growth annealing conditions, heterostructures with ns of 1013–1016 cm−2 are achieved. The atomic-scale structure of the samples is obtained using high-resolution synchrotron x-ray diffraction measurements. For heterostructures with ns at or below 3 × 1013 cm−2, polar distortions are present within the LCO layers and increase in magnitude with a decrease in sheet carrier concentration. These distortions are absent for samples with ns on the order of 1015–1016 cm−2 where interfacial carriers play a role in alleviating the polar discontinuity at the LCO/STO interface. These results suggest that interfacial charge carriers and polar distortions can act as complementary mechanisms to alleviate the polar discontinuity at polar/non-polar complex oxide interfaces.

Highlights

The discovery of emergent electronic and magnetic phenomena at polar/non-polar perovskite oxide interfaces not found in bulk has sparked considerable interest by the scientific community.1–5 At such interfaces, the discontinuity in the charge stacking leads to a polar catastrophe characterized by the divergence of the electrostatic potential with an increase in the thickness of the polar material
For the LCO layers and increase in magnitude with a heterostructures decrease in sheet with ns at or below 3 carrier concentration. These distortions are absent for samples with ns on the order of 1015–1016 cm−2 where interfacial carriers play a role in alleviating the polar discontinuity at the LCO/STO interface. These results suggest that interfacial charge carriers and polar distortions can act as complementary mechanisms to alleviate the polar discontinuity at polar/non-polar complex oxide interfaces
In this Letter, we focus on the relationship between ionic structural relaxations that arise to screen the electric field within the polar layer and the interfacial charge density at the interface between (001)-oriented polar LaCrO3(LCO) films and non-polar SrTiO3(STO)

Summary

Introduction

The discovery of emergent electronic and magnetic phenomena at polar/non-polar perovskite oxide interfaces not found in bulk has sparked considerable interest by the scientific community. At such interfaces, the discontinuity in the charge stacking leads to a polar catastrophe characterized by the divergence of the electrostatic potential with an increase in the thickness of the polar material. The discovery of emergent electronic and magnetic phenomena at polar/non-polar perovskite oxide interfaces not found in bulk has sparked considerable interest by the scientific community.1–5 At such interfaces, the discontinuity in the charge stacking leads to a polar catastrophe characterized by the divergence of the electrostatic potential with an increase in the thickness of the polar material. In this Letter, we focus on the relationship between ionic structural relaxations that arise to screen the electric field within the polar layer and the interfacial charge density at the interface between (001)-oriented polar LaCrO3(LCO) films and non-polar SrTiO3(STO).. The critical thickness for metallicity, intrinsic (electronic reconstruction) and extrinsic (e.g., arising from oxygen vacancies) charge carriers at the interface can provide additional screening of the electric field within the polar film. We perform a systematic study of the LCO/STO interfacial carrier concentration that can be tuned by growth and post-growth conditions and their relation to the lattice polarization to develop a comprehensive understanding of the unique physical properties that emerge at polar/non-polar interfaces

Methods

Results

Conclusion