École Polytechnique Fédérale de Lausanne
报告摘要：
Perovskite-structured transition metal oxide compounds continue to stimulate strong research interest, owing to their potential for creating novel functional electronic and magnetic properties, by exploiting the correlation between different degrees of freedom (spin, charge, lattice, orbital, topology). One of the main ways researchers pursue these goals is the deposition of thin films and heterostructures, where composition and epitaxial strain are used to study and engineer their physical properties. Paramount to this research is the precise, metrological characterization of the synthesized lattices at the atomic scale, for verifying expectations, correlating to their physical nature, and uncovering new structural phenomena. Towards this end, here, I discuss the role of aberration-corrected scanning transmission electron microscopy (Cs-STEM) and spectroscopy. In a first example, the case of rare earth nickelate superlattices will be presented, where Cs-STEM imaging and electron energy-loss spectroscopy are vital for understanding the influence of superlattice interfaces and length-scales on the metal-to-insulator transition [1, 2]. Next, I consider LaVO3 layers where, via careful measurements in STEM imaging and 4D-STEM diffraction, we identify a novel, atomically-sharp structural interface formed in a single compound, that we term the switching plane. Induced by imposing a structural-energetic conflict during the growth of this orthorhombic compound, we further rationalize its formation using second-principles calculations involving thousands of atoms [3]. Finally, I turn our attention to the recent field of oxide membranes, where we go beyond pure interface characterization to in-situ interface creation. Specifically, we use the local STEM raster scan to create ionically bonded crystalline lattice between a thermally annealed combination of SrTiO3 membrane mechanically transferred to a Nb-doped SrTiO3 carrier substrate. This approach opens the possibility for the deterministic writing of strained interfaces for new functional applications [4].
[1] C. Domínguez et al., Nature Mater. 19 (2020) 1182–1187.
[2] B. Mundet et al., Nano Lett. 21 (2021) 2436–2443.
[3] D.T.L. Alexander et al., ACS Nano 19 (2025) 10126–10137.
[4] G. Segantini et al., Nano Lett. 24 (2024) 14191–14197.
报告人简介：
Dr. Duncan Alexander is a senior researcher and electron microscopist at EPFL in Switzerland, specialized in the development, application and teaching of advanced transmission electron microscopy techniques. In this role, he brings over two decades of experience across a transdisciplinary array of research subjects, with publications on topics ranging from thin films and condensed matter physics to metallurgy, atmospheric aerosols, and nano-photonics. After a PhD in materials science at the University of Cambridge, and postdoctoral research positions at the University of Sydney and Arizona State University, he arrived at EPFL in 2007. After holding a post as a staff scientist at the Interdisciplinary Centre for Electron Microscopy (CIME) platform facility, in 2018 he switched to a research and teaching specialization as senior microscopist in the Electron Spectrometry and Microscopy Laboratory (LSME) in the Institute of Physics in 2018. Currently, his research is focused on aberration-corrected scanning transmission electron microscopy and spectroscopy data acquisition and processing, with particular interests in atomic metrology across oxide interfaces, and high spatial–spectral resolution electron energy-loss spectroscopy. As well as research, Duncan Alexander teaches on transmission electron microscopy and spectroscopy, from fundamentals to advanced techniques, at masters and doctoral levels. With LSME director Prof. Cécile Hébert, he is the co-creator of the online course Transmission Electron Microscopy for Materials Science (https://www.edx.org/learn/physics/ecole-polytechnique-federale-de-lausanne-transmission-electron-microscopy-for-materials-science).
邀请人：孙永昊
联系电话：82649303
地点：物理所D楼208会议室