Low- Temperature Transformations in Amorphous Silica Bilayers on Ru(0001) After Crystal-Glass Transition: Closer Look.

The crystal-glass transition concerning silicon dioxide has been a topic of intense research. It has been possible to prepare a bilayer silica film on a metal substrate and study the corresponding transition in real space using scanning tunneling microscopy (STM). While the initial trigger of the transition has been identified as a so-called Stone-Wales ring-opening process, which requires rather high energies/temperatures, a question has been, whether there are similar follow-up processes, which require much less energy and thus rather moderate temperatures. Although observations have been reported using electron microscopy, it remains unclear whether, in this case, the modifications were initiated by the measurement itself. Here, we report on a fast-scanning STM study, allowing a study in real space and indicating structural transformations at room temperature. The experimental results are supported by demanding density functional calculations, which allow for an understanding of the involved ring structure modifying processes. The calculations also reveal the influence of the metal support on the transformation energetics.