Near-Atomic-Scale Compositional Complexity in a 2D Transition Metal Oxide

TL;DR

This study uses atom probe tomography to reveal near-atomic-scale compositional deviations in 2D Ti0.87O2, highlighting the importance of detailed analysis for optimizing 2D material properties in nanoelectronics.

Contribution

It provides the first detailed atomic-scale compositional analysis of 2D Ti0.87O2, revealing deviations from ideal stoichiometry and their implications for material properties.

Findings

Revealed oxygen vacancies and alkali metal retention in 2D Ti0.87O2

Identified a reconstruction mechanism mitigating vacancy effects

Highlighted the importance of detailed compositional analysis

Abstract

2D materials hold transformative promise for next-generation nanoelectronics. However, successfully integrating these materials from laboratory-scale discoveries into real-world devices depends on precisely controlling their properties, which are fundamentally determined by their composition. Detailed characterisation using atom probe tomography of 2D Ti0.87O2, a candidate high-$\kappa$ dielectric, reveals deviations from its commonly assumed stoichiometry. Compositional analysis and comparison with the bulk K0.8[Ti1.73Li0.27]O4 precursor evidences an oxygen deficit indicative of oxygen vacancy formation in the 2D material, as well as the retention of low concentrations of alkali metals that were presumed to be removed during synthesis. Such deviations from stoichiometry indicate a reconstruction mechanism that mitigates the effect of the characteristic, negatively charged vacancies on the titanium sublattice, thereby influencing the local electronic structure and, consequently, functional properties. These findings underscore the importance of a detailed compositional analysis in both understanding and optimizing the extraordinary functional properties of 2D materials, opening pathways to tailored functionalities in next-generation nanoelectronics.