Surface telluride phases on Pt(111): Reconstructive formation of unusual adsorption sites and well-ordered domain walls

For the production of transition-metal dichalcogenides by molecular beam epitaxy, an understanding of the interaction between chalcogenide atoms and metal surfaces is of fundamental interest. Here, we describe the occurrence of stable surface telluride phases when reacting submonolayer amounts of tellurium with a Pt(111) surface. We find that when approaching a Te amount of 0.44 monolayers from below, a disordered Te adsorbate phase is converted into a long-range ordered Pt(111)-(3 x 3)-4Te surface telluride, which is stable against loss of Te up to 890 K. Adding further Te, heavy domain walls develop that condense into a well-ordered domain structure with (10 x 10) periodicity. It hosts 49 Te atoms per unit cell and is thermally stable up to 770 K. These two phases are the only existing Te-induced surface reconstructions in the submonolayer regime. The atomic structure of the two phases is determined using low-energy electron diffraction intensity analysis, scanning tunneling microscopy, and density functional theory. The resulting complex surface structures are revealed with picometer accuracy and a great agreement between the employed methods. In particular, the analysis of the (10 x 10) structure demonstrates the currently achievable state-of-the-art for low-energy electron diffraction structural analyses in terms of experimental surface preparation and data collection but also of computational methods, and it leads the way to building up a structural database for two-dimensional materials and their interfaces.