Ultrathin Silica Films: The Atomic Structure of Two-Dimensional

Abstract: For the last 15 years, we have been studying the preparation and characterization of ordered silica films on metal supports. We review the efforts so far, and then dis-cuss the specific case of a silica bilayer, which exists in a crys-talline and a vitreous variety, and puts us into a position to investigate, for the first time, the real space structure (AFM/ STM) of a two-dimensional glass and its properties. We show that pair correlation functions determined from the images of this two-dimensional glass are similar to those deter-mined by X-ray and neutron scattering from three-dimen-sional glasses, if the appropriate sensitivity factors are taken into account. We are in a position, to verify, for the first time, a model of the vitreous silica structure proposed by William Zachariasen in 1932. Beyond this, the possibility to prepare the crystalline and the glassy structure on the sam