Stoichiometry-Driven Formation of Two-Dimensional Ternary Oxides: From Quasicrystal Approximants to Honeycomb Lattice Structures
Résumé
The spontaneous ordering of a two-dimensional (2D) SrTiO3-derived film supported on Pt(111)/Al2O3(0001) is investigated by scanning tunneling microscopy. After annealing under ultrahigh vacuum, a 2D reduced wetting layer is formed where oxide quasicrystal approximants are observed. Upon increasing the number of preparation cycles, the Sr content in the film decreases. The structure of the film then evolves into a Ti2O3 honeycomb (HC) lattice partially decorated by Sr adatoms. The latter is localized in hollow sites of the network, with several complex structures resulting from the Sr occupation rate. A labyrinth-like phase was identified as well as an ordered (√3 × √3)R30° phase, where only 1/3 of the hollow sites of the HC lattice are occupied. Those results suggest that the phase sequence is driven by a stoichiometry change that is mainly controlled by the Sr/(Ti2O3) ratio
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