Van Marum Colloquium - Crystal growth far from equilibrium: beauty and puzzles of Pt(111)
- Tuesday 7 February 2023
2333 CC Leiden
Under conditions typical for thin film growth, gas phase crystal growth far from thermodynamic equilibrium allows one to investigate in a simple and clear way kinetic effects in growth.
Pronounced mound formation is observed on Pt(111) and many other metal surfaces during homoepitaxy in a certain temperature range. In this regime the fundamental parameters of surface diffusion can be read directly from the fundamental length scales of the morphology - as observed for instance by scanning tunneling microscopy.
The Pt(111) surface is fundamentally unstable against external perturbation due to its large inherent tensile surface stress. While reconstructed in a complex fashion at temperatures above 1330 K in equilibrium, depending on the chemical potential of the Pt adatoms also at temperatures close to ambient Pt(111) can be reconstructed. The pronounced and long lasting layer-by-layer growth observed above 550 K initially puzzled the community and was interpreted as to result from magic clusters. Instead, it is the consequence of the dynamic surface reconstruction of Pt(111) pulsing during deposition with monolayer period.
In the last part of the talk a new type of two dimensional material will be introduced, namely cluster superlattice membranes. It is argued that a dense array of small Pt clusters (cluster size a few to a few 100 atoms) largely embedded in a nm-thick matrix of amorphous C could be an electrocatalyst with an extreme resistance against sintering.