The seminar will take place at the Sala d'Actes Carles Miravitlles
Mapping structural rippling and strain in van der Waals heterostructures
by Gabriel Sánchez Santolino, from Universidad Complutense de Madrid, Dept. Física de Materiales
Wednesday, 26 October 2022
ICMAB-Sala d'Actes Carles Miravitlles
The functional properties of van der Waals (vdW) two-dimensional materials are highly sensitive to structural distortions such as ripplings or corrugations. In franckeite, a naturally occurring vdW heterostructure, we have shown how a mismatch between its constituent pseudohexagonal and pseudotetragonal two-dimensional layers gives rise to a spontaneous rippling that is responsible for a strong anisotropic strain that affects the electrical, vibrational, and optical properties of the material . Moreover, small variations in the multilayered structure and composition of this material can give rise to a strong topological insulator phase .
In this seminar we will talks about how four-dimensional scanning transmission electron microscopy (4D-STEM) can allow us to map the local structural modulations occurring in this material and characterize the strong strain fields arising from a 3D structural rippling. In 4D-STEM, we measure a full 2D image of the transmitted electron beam, or a convergent beam electron diffraction pattern (CBED) as the electron beam is raster scanned over a 2D grid of probe positions in real space, as schematized in the figure below (Fig. 1) 4D-STEM brings thus a new pathway to study the structural and physical properties of 2D materials and heterostructures.
Schematic of a four-dimensional scanning transmission electron microscopy experiment (Fig. 1)
 R. Frisenda, G. Sanchez-Santolino, N. Papadopoulos, J. Urban, M. Baranowski, A. Surrente, D.K. Maude, M. Garcia-Hernandez, H. S. J. van der Zant, P. Plochocka, P. San-Jose and A. Castellanos-Gomez, Nano Letters, 20 2 (2020) 1141–1147
 W. S. Paz, M. G. Menezes, N. N. Batista, G. Sanchez-Santolino, M. Velický, M. Varela, R. B. Capaz and J. José Palacios, Nano Letters, 21 18 (2021) 7781-7788
Graduated in Physics in 2009 at UCM, MSc in 2010 and PhD in 2015 concerning Advanced electron microscopy characterization of complex oxide interfaces, with supervisors Prof. María Varela and Prof. Jacobo Santamaría. Visiting researcher at Oak Ridge National Laboratory (USA) in the STEM Group with Prof. Stephen J. Pennycook during the PhD thesis. Between 2015 and 2017, RISING II Post-Doctoral Project Researcher at The University of Tokyo (Japan) in the Institute of Engineering Innovation, in the Crystal Interface Laboratory, on analysis of electromagnetic fields at atomic resolution, with supervisors Prof. Yuichi Ikuhara and Prof. Naoya Shibata. From 2017 to 2019, Juan de la Cierva Post-Doctoral Fellow at Spanish Research Council (CSIC) in the Instituto de Ciencia de Materiales de Madrid (ICMM), in the 2D Foundry group, followed by 6 months as ESTEEM3 Researcher at Chalmers University of Technology (Sweden) in the Department of Physics, in the Eva Olsson Group. Since November 2019, Jóvenes Investigadores (JIN) Researcher at Universidad Complutense de Madrid.
Hosted by Jaume Gázquez, MULFOX group, ICMAB-CSIC