Chagas, Thaís
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Publication Access status: Metadata only , Dislocation-free two-dimensional concentric lateral heterostructures: MoS2–TaS2/Au(111)We prepared two-dimensional concentric lateral heterostructures of the monolayer transition metal dichalcogenides MoS 2 and TaS 2 by reactive molecular beam epitaxy on chemically inert and weakly interacting Au(111). The heterostructures are in a size regime where quantum confinement can be expected. Despite large lattice mismatch a seamless interconnection of the two materials has been achieved, confirming that the semiconducting core is fully enclosed by a metallic border around its circumference. The resulting strain is analyzed on the atomic scale using scanning tunneling microscopy, corroborated by calculations based on empirical potentials and compared to results from finite elements simulations.Source Type:Article2 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Metadata only , Phase engineering in tantalum sulfide monolayers on Au(111)We prepare monolayers of tantalum sulfide on Au(111) by evaporation of Ta in a reactive background of H 2 S. Under sulfur-rich conditions, monolayers of 2H-TaS 2 develop, whereas under sulfur-poor conditions TaS forms, a structure that can be derived from 2H-TaS 2 by removal of the bottom S layer. We analyze the alignment of the layers with respect to the substrate and the relation with the domains in the Au(111) herringbone reconstruction using scanning tunneling microscopy. With the help of density functional theory calculations we can determine the registry of the two phases with the substrate. We develop a growth process that allows preparation of uniquely oriented 2H-TaS 2 on Au(111). 2H-TaS 2 and TaS have a remarkably similar in-plane lattice structure and we observe the formation of lateral 2H-TaS 2 -TaS heterostructures with atomically well-defined and defect-free boundaries. We observe mirror twin boundaries within 2H-TaS 2 along the S- and Ta-edge.Source Type:Article6 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Metadata only , Transition from fractal-dendritic to compact islands for the 2D-ferroelectric SnSe on graphene/Ir(111)Epitaxial growth is a versatile method to prepare two-dimensional van der Waals ferroelectrics like group IV monochalcogenides which have potential for novel electronic devices and sensors. We systematically study SnSe monolayer islands grown by molecular beam epitaxy, especially the effect of annealing temperature on shape and morphology of the edges. Characterization of the samples by scanning tunneling microscopy reveals that the shape of the islands changes from fractal-dendritic after deposition at room temperature to a compact rhombic shape through annealing, but ripening processes are absent up to the desorption temperature. A two-step growth process leads to large, epitaxially aligned rhombic islands bounded by well-defined $\left\langle 110\right\rangle $ -edges (armchair-like), which we claim to be the equilibrium shape of the stoichiometric SnSe monolayer islands. The relaxation of the energetically favorable edges is detected in atomically resolved STM images. The experimental findings are supported by the results of our first-principles calculations, which provide insights into the energetics of the edges, their reconstructions, and yields the equilibrium shapes of the islands which are in good agreement with the experiment.Source Type:Article2
