Synthesis of epitaxial monolayer Janus SPtSe
Roberto Sant, Maxime Gay, Alain Marty, Simone Lisi, Rania Harrabi, Céline Vergnaud, Minh Tuan Dau, Xiaorong Weng, Johann Coraux, Nicolas Gauthier, Olivier Renault, Gilles Renaud, Matthieu Jamet
Abstract
Abstract Janus single-layer transition metal dichalcogenides, in which the two chalcogen layers have a different chemical nature, push chemical composition control beyond what is usually achievable with van der Waals heterostructures. Here, we report such a Janus compound, SPtSe, which is predicted to exhibit strong Rashba spin–orbit coupling. We synthetized it by conversion of a single-layer of PtSe 2 on Pt(111) via sulfurization under H 2 S atmosphere. Our in situ and operando structural analysis with grazing incidence synchrotron X-ray diffraction reveals the process by which the Janus alloy forms. The crystalline long-range order of the as-grown PtSe 2 monolayer is first lost due to thermal annealing. A subsequent recrystallization in presence of a source of sulfur yields a highly ordered SPtSe alloy, which is isostructural to the pristine PtSe 2 . The chemical composition is resolved, layer-by-layer, using angle-resolved X-ray photoelectron spectroscopy, demonstrating that Se-by-S substitution occurs selectively in the topmost chalcogen layer.