Atomic structure of a metal-supported two-dimensional germania film

Abstract

The growth and microscopic characterization of two-dimensional germania films is presented. Germanium oxide monolayer films were grown on Ru(0001) by physical vapor deposition and subsequent annealing in oxygen. We obtain a comprehensive image of the germania film structure by combining intensity-voltage low-energy electron diffraction (I/V-LEED) and ab initio density functional theory (DFT) analysis with atomic-resolution scanning tunneling microscopy (STM) imaging. For benchmarking purposes, the bare Ru(0001) substrate and the (2 × 2)3O covered Ru(0001) were analyzed with I/V-LEED with respect to previous reports. STM topographic images of the germania film reveal a hexagonal network where the oxygen and germanium atom positions appear in different imaging contrasts. For quantitative LEED, the best agreement has been achieved with DFT structures where the germanium atoms are located preferentially on the top and fcc hollow sites of the Ru(0001) substrate. Moreover, in these atomically flat germania films, local site geometries, i.e., tetrahedral building blocks, ring structures, and domain boundaries, have been identified, indicating possible pathways towards two-dimensional amorphous networks.

Assessing the film-substrate interaction in germania films on reconstructed Au(111)

“…In fact, the weak coupling to the substrate is responsible for the randomly oriented unit blocks of SiO 4 that give rise to amorphous networks. In our recently reported ultrathin germania films on Ru(0001) and Pt(111), we observe a similar correlation between the atomic structure of the film and the metal support to the one in the silica films [39][40][41]. While on Ru(0001) germania forms very stable hexagonal monolayer films [39] and ill-defined bilayer films [40], on Pt(111) forms a wide range of structures: monolayer films, crystalline and amorphous bilayer films [41], and a zigzag-line phase (comparable to the silica one [59]).…”

“…The preparation procedure of the films follows the steps reported previously for germania films supported on Ru(0001) and Pt(111) [39][40][41]. The Au(111) single crystal surface is cleaned by several cycles of sputtering and annealing at 820 K for 15 min.…”

Modelling the atomic arrangement of amorphous 2D silica: a network analysis

“…Recently, a germania analogue of a silica film has been prepared in a monolayer form ref. 49 with strong substrate interaction. Investigations are ongoing to synthesize germania in a bi-layer form, which also may be a potential candidate for the application of a Yukawa-type model.…”

Growth and Atomic‐Scale Characterization of Ultrathin Silica and Germania Films: The Crucial Role of the Metal Support

“…To obtain a more general picture of 2D glasses, ultrathin germania films have been successfully synthesized and characterized at the atomic scale on Ru(0001), [17, 18] Pt(111), [19] and Au(111) [20] . These metal supports exhibit different lattice constants and significantly different chemical reactivities, so that each of them promotes the formation of different germania polymorphs.…”