SKM 2023 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 40: 2D Materials V: Growth, Structure and Substrate Interaction (joint session O/CPP)

CPP 40.6: Talk

Wednesday, March 29, 2023, 16:15–16:30, GER 37

Structure determination of mono- and few-layers of the 2D-ferroelectric SnSe on graphene on Ir(111) — •Dina Wilks¹, Paulus Aleksa¹, Simon Chung², Peter Modregger¹, Dmitri V. Novikov³, Vedran Vonk², Andreas Stierle^2,4, and Carsten Busse¹ — ¹Physics Department, University of Siegen, Germany — ²Nanolabor Centre for X-ray and Nano Science CXNS, Germany — ³Deutsches Elektronen-Synchrotron DESY, Germany — ⁴Physics Department, University of Hamburg, Germany

For conventional ferroelectrics the critical temperature T_c quickly falls below technically feasible values for very thin films. This is not the case for two-dimensional materials. Theory predicts strong ferroelectricity for group-IV monochalcogenides, where individual layers are puckered sheets with a phosphorene-like structure. For SnSe, stable ferroelectricity of monolayers at room temperature has been shown by controlled microscopic manipulation. Here, we provide the missing structure determination of these monolayers.
We use surface X-ray diffraction to determine the structure of SnSe mono- and few-layers, the influence of the substrate, and the difference in stacking between a few-layered system and the bulk. SnSe films are prepared by MBE using graphene on Ir(111) as an inert and weakly interacting substrate. We observe one phase with three different orientations of monolayer SnSe islands with respect to graphene, while for the few-layered system two phases are found, each with three different orientations. A change in structure with rising temperature for both systems is seen, which hints towards T_c.