Atomic Arrangement in Two-Dimensional Silica: From Crystalline to Vitreous Structures

The atomic structure of vitreous and crystalline regions of a thin silica film on Ru(0001) was investigated using noncontact atomic force microscopy (nc-AFM) and scanning tunneling microscopy (STM). We were able to resolve the atomic arrangement of the Si and the O atoms in the crystalline and the vitreous structures. We discuss characteristic structural properties of the films, such as distances, orientations, and angles, and we compare our results to experiments and simulations of bulk vitreous silica networks. It was found that order in two-dimensional vitreous networks can extend up to 2 nm.