Correlated diffusion investigated by low-temperature scanning tunneling microscopy

Ch. Zaum and K. Morgenstern

Chair of Physical Chemistry I, Ruhr-Universit├Ąt Bochum, Germany

As part of reactions, the motion of adparticles on surfaces is a particular active area of research, because a variety of basic physical and chemical processes start with the transport of objects on a surface. For instance in heterogeneous catalysis, the reactants have to diffuse to active sites, at which the actual reaction proceeds. The mobility of the objects frequently limits the overall reaction rate. Atomic diffusion has therefore been studied intensively, however, mostly at dilute coverage. At realistic conditions, adsorbate interactions might alter diffusion rates. Indeed, our time-lapsed studies of CO diffusion on Ag(100) and on Cu(111) in the temperature range below 50 K [1] reveal a multitude of interactions that alter the overall diffusion rate. On Ag(100), the short-range interactions enhance the diffusion rates by orders of magnitude. On Cu(111), long-range interactions as mediated by surface states influence diffusivities [2]. Moreover, we present evidence for a many-body interaction. The effect of the interaction is surprisingly different, if diffusion is induced by fs-laser irradiation [3]. The origins of the different phenomena will be discussed.

[1] Christopher Zaum, Cord Bertram, Kastur M. Meyer auf der Heide, Michael Mehlhorn, Karina Morgenstern, Review of scientific instrumentation 87, 053902 (2016)

[2] Christopher Zaum, Karina Morgenstern, Nano Letters 16 (2016) 3001

[3] Christopher Zaum, Kastur M. Meyer-auf-der-Heide, Michael Mehlhorn, Steve McDonough, William F. Schneider, Karina Morgenstern, Physical Review Letters 114 (2015) 146104