Berlin 2024 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 6: Thin Film Properties I

DS 6.7: Vortrag

Dienstag, 19. März 2024, 11:45–12:00, A 060

Precision Through Precession: Enhanced Accuracy of Strain Investigations in Scanning Transmission Electron Microscopy — •Rahel Specht, Frederik Otto, Laura Niermann, Tore Niermann, and Michael Lehmann — Technische Universität Berlin, Germany

In semiconductor development, strain engineering plays a pivotal role, for example in enhancing piezoelectrical effects in AlGaN quantum wells. With ever decreasing device sizes, knowledge of interacial strain at high spatial resolution is an important feedback for the manufacturing process. Scanning Transmission Electron Microscopy (STEM) is capable of resolving the local lattice spacing with nanometer resolution by scanning a focused electron probe over the sample and evaluating the distance of diffraction discs at each respective beam position. However, due to multiple electron scattering and subsequent interference, intensity variations appear in the resulting diffraction discs. These variations hinder the precise detection of the disc’s position in the diffraction pattern. In this work, we employ a precessing electron beam to map the position-dependent measurement of lattice spacing of (Al,Ga)N in GaN. Precessing the electron beam effectively averages multiple diffraction patterns, resulting in a more uniform intensity distribution in the diffraction discs. While larger precession angles enhance the precision of disc detection, due to microscope aberrations, higher precession angles also lead to a reduction in spatial resolution. Therefore, we aim to outline a pathway to determining optimal settings for high-resolution strain measurements at heterointerfaces in STEM.

Keywords: Strain; (Scanning) Transmission Electron Microscopy; Electron Diffraction; Heterointerfaces; Precision Measurements