The impact of sample misalignment and overlap on high-resolution quantification of 2D-metal heterostructures

Abstract

Precise atomic-scale fabrication of two-dimensional (2D) semiconductor metal heterostructures necessitates an in-depth understanding of their surface atomic arrangements, interfacial atomic configurations, and electronic state. The foundation for achieving this understanding lies in the accurate characterization of these heterostructures. Aberration-corrected transmission electron microscopy (ACTEM) is capable of simultaneously obtaining critical information regarding atomic arrangements, electronic states, and elemental distributions at the atomic scale, making it widely utilized for the analysis and characterization of heterostructures. However, the accuracy of ACTEM can be compromised by sample overlaps in high-resolution images, a challenge particularly pronounced in 2D-semiconductor-metal heterostructures. To address this, we selected Pt-MoS₂ as a model system and systematically investigated the effects of misalignment and sample overlap on quantitative electron microscopy analysis of two-dimensional semiconductor heterostructures through high-resolution image simulations. Our findings reveal that even small misalignments (< 2°) introduce errors of approximately ∼2 % in the analysis of interplanar spacing. Furthermore, the overlap of the MoS₂ potential function can induce apparent strain (>5 %) in high-resolution TEM (HRTEM) image. Notably, the apparent strain from potential function overlap remains within an acceptable range only when the relative thickness ratio of metal to 2D substrate exceeds a certain threshold, improving the reliability of direct quantitative analysis of HRTEM images. Additionally, we applied a digital dark-field method that effectively mitigates the influence of the substrate on metal atomic column contrasts, thus improving the accuracy of quantitative analysis in HRTEM images. Collectively, these results provide a deeper understanding of the heterostructure imaging and the precise characterization of the 2D-material-metal heterostructure.