Dynamic surface processes viewed by scanning tunneling microscopy

Scanning tunneling microscopy (STM) has at its core a very simple idea: a sharp metallic needle is approached very close to a conductive surface while a bias voltage between the tip and the surface is applied. Thanks to this simple principle a wide variety of surface structures and processes have been studied and revealed.
To keep surfaces clean and to keep atoms stationary during the measurement, STM experiments are often carried out in ultra–high vacuum and cryogenic temperatures. It makes experiments simpler and makesresults easier to interpret. However, it also makes experiments more distant from applications that usually operate at room (or higher) temperature and in atmospheric (or higher) pressure.
In this talk, we will present the results of two sets of STM studies executed either at room (or elevated) temperature or at elevated pressure. The first set of studies deals with the interaction of organic molecules with metal–passivated silicon surfaces, in particular interaction of Cu–phthalocyanine molecules (CuPc) with the thallium–passivated Si(111) surface. CuPs molecules form a 2D molecular gas on the surface. We will show how the gas can be directly visualized and affected by means of the STM. The second part of the presentation will be devoted to catalytically active surfaces imaged by near–ambient pressure STM. We will demonstrate that the elevated gas pressure can induce restructuring of a surface and we will discuss the consequences of the restructuring for a chemical activity of studied surfaces.