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O: Fachverband Oberflächenphysik
O 90: 2D Materials VI: Growth, Structure and Substrate Interaction
O 90.12: Talk
Thursday, March 21, 2024, 17:45–18:00, MA 005
Growth and structure of Chromium sulfide: a new magnetic 2D material — •Affan Safeer1, Mahdi Ghorbani Asl2, Wouter Jolie1, Hannu Pekka Komsa3, Arkady V. Krasheninnikov2, Thomas Michely1, and Jeison Fischer1 — 1Universität zu Köln, Köln, Germany — 2Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany — 3University of Oulu, Oulu, Finland
We combine scanning tunneling microscopy (STM), low-energy electrons diffraction (LEED) and density functional theory (DFT) calculations to investigate growth, structure and properties of chromium sulfides fabricated by molecular beam epitaxy on graphene. The thinnest chromium sulfide formed has threefold symmetry, an in-plane lattice parameter of 0.340 +/- 0.002 nm, apparent STM height of 0.78-0.87 nm, and 2 Cr atoms per unit cell. Upon annealing of the thinnest, phase pure layers, compounds with same symmetry and lattice parameter, but with increased height in steps of 0.24 nm are formed. In combination with DFT calculations we find a five-layer stack S-Cr-S-Cr-S, namely Cr2S3, to yield excellent agreement with the experimental observations. Systematic variation of the stacking sequence in the DFT calculations of five- layer stacks makes plain, that Cr2S3 grows in the NiAs-structure. Thicker layer, as observed after annealing, are formed by covalent growth of multiples of additional CrS layers. Spin-polarized STM of Cr2S3 at 1.7 K displays hysteresis of the differential conductance signal as a function of out-of-plane magnetic field. This hysteresis is consistent with a ferromagnetic response of the top Cr-layer and antiferromagnetic alignment between Cr layers in Cr2S3.
Keywords: Chromium Sulfide; 2D magnetic material; Scanning tunneling microscopy; two-dimensional material