Atomic-Scale Roughness of Freestanding Oxide Membranes Revealed by Electron Ptychography

TL;DR

This paper introduces a high-precision electron ptychography method to map atomic-scale surface roughness and interfaces in freestanding oxide membranes, crucial for quantum device performance.

Contribution

It develops a novel 3D electron ptychography technique for atomic-scale surface and interface mapping in ultrathin oxide structures, including light elements like oxygen.

Findings

Achieved atomic-scale topography mapping of free surfaces and buried interfaces.

Enabled counting of atoms, including light elements, in electron microscopy.

Provided detailed insights into structural inhomogeneities affecting quantum device performance.

Abstract

Freestanding oxide films offer significant potential for integrating exotic quantum functionalities with semiconductor technologies. However, their performance is critically limited by surface roughness and interfacial imperfection caused by dangling bonds, which disrupt coherent interactions and suppress quantum phenomena at heterointerfaces. To address the challenge of structural characterization of surfaces and interfaces, we develop a metrological approach achieving atomic-scale precision in mapping the topography of both free surfaces and buried interfaces within ultrathin oxide heterostructures leveraging three-dimensional structures reconstructed from multislice electron ptychography. This method also allows for counting the number of atoms, even including light elements such as oxygen, along the electron trajectory in electron microscopy, leading to the identification of surface termination in oxide films. The planar-view of measurement geometry, allowing for large field-of-view imaging, provides remarkably rich information and high statistics about the atomic-scale structural inhomogeneities in freestanding membranes. This quantitative analysis provides unprecedented capabilities for correlating structural imperfection with quantum device performance, offering critical insights for engineering robust heterointerfaces in next-generation oxide electronics.