Schwingenschlögl, Udo
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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 , Tin Halide Perovskite Epitaxial Films on Gold Surfaces: Atomic Structure and StabilityTin‐based halide perovskite solar cells can be efficient and environmentally friendly substitutions to lead‐based halide perovskite solar cells, but they have a drawback due to oxidation from Sn 2+ to Sn 4+ . Using vacuum deposition, epitaxially aligned CsSnBr 3 ultrathin films are prepared on Au(111) and Au(100) and characterized with scanning tunneling microscopy (STM), low‐energy electron diffraction (LEED), and X‐ray photoelectron spectroscopy (XPS). By co‐evaporation of the precursor molecules CsBr and SnBr 2 , few monolayers of perovskite are obtained. On Au(111), CsSnBr 3 grows in three differently oriented domains due to the hexagonal symmetry of the substrate. On Au(100), which has square symmetry, identical to CsSnBr 3 , but with about half the lattice constant of the perovskite, a (2×2) superstructure is observed. The perovskite is terminated with the (001) facet showing a square surface structure in agreement with density functional theory (DFT) calculations. Chemical analysis is performed in ultra‐high vacuum (UHV) conditions and no indication of a tin oxidation state higher than Sn 2+ is found in the films. However, after exposure to air, rapid and severe changes in the films are observed, highlighting the importance of preparing tin perovskites in a controlled environment to maintain their stability and avoid oxidation‐related issues.Source Type:Article3
