Antiphase Domain Boundary Formation in 2D Ba–Ti–O on Pd(111): An Alternative to Phase Separation

Le résumé fourni par la source

2D oxide quasicrystals (OQCs) are unique structures arising from atoms positioned at the vertices of a dodecagonal triangle–square–rhombus tiling. The prototypical example for OQCs is derived from BaTiO3 on Pt(111). Herein, scanning tunneling microscopy (STM) and low‐energy electron diffraction (LEED) investigations of 2D oxide layers derived from BaTiO3 on Pd(111) are reported. Upon ultrahigh vacuum (UHV) annealing, different long‐range ordered structures are observed with a base of four vertex atoms forming two edge‐sharing equilateral triangles. By a periodic repetition of this base in either quadratic or rectangular unit cells, a triangle–square tiling (known as σ‐phase approximant or 32.4.3.4 Archimedean tiling) or a triangle–rhombus tiling is formed. Both structures vary strongly in their vertex density. In addition, the formation of antiphase domain boundaries in the σ phase is observed resulting in a well‐ordered incorporation of rhombuses in the triangle–square tiling. A systematic variation of the frequency of these domain boundaries is identified as a mechanism for an incremental increase in the global vertex density, mediating between pure triangle–square and triangle–square–rhombus tilings.

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