Twisting and Rippling of a Two-Dimensional Kagome Lattice: Silica on Au(111)

The intrinsic properties of two-dimensional (2D) SiO2 were revealed by forming the material on inert Au(111). Growth by SiO deposition enabled formation of a crystalline phase consisting of two linked sheets of six-membered rings of tetrahedral [SiO4] building units. The bases of the tetrahedra form an isostatic 2D kagome lattice. The weak interaction with Au allowed a new corrugation of the 2D material to be detected: ripples with a ∼4 nm periodicity that help stabilize the 2D crystalline layer. On the atomic scale, substantial distortions from ideal hexagonal rings were observed even though crystalline defects were extremely rare. The ring distortions were reproduced in theoretical models that showed that they were associated with a twisting of the 2D kagome lattice, which stabilizes the material when subjected to disturbances. The twisting and rippling impart 2D silica with the flexibility to adapt to strain and changes in the crystallographic direction without introducing defects.