Growth and decay of a two‐dimensional oxide quasicrystal: High‐temperature in situ microscopy

The recently discovered two‐dimensional oxide quasicrystal (OQC) derived from BaTiO3 on Pt(111) is the first material in which a spontaneous formation of an aperiodic structure at the interface to a periodic support has been observed. Herein, we report in situ low‐energy electron microscopy (LEEM) studies on the fundamental processes involved in the OQC growth. The OQC formation proceeds in two steps via of an amorphous two‐dimensional wetting layer. At 1170 K the long‐range aperiodic order of the OQC develops. Annealing in O2 induces the reverse process, the conversion of the OQC into BaTiO3 islands and bare Pt(111), which has been monitored by in situ LEEM. A quantitative analysis of the temporal decay of the OQC shows that oxygen adsorption on bare Pt patches is the rate limiting step of this dewetting process.