Insight into heterogeneous dynamics of growing islands using coherent x-ray scattering

Abstract

Understanding the non-equilibrium structure formation of thin films is a fundamental challenge with important implications also for technical applications. The interplay between adsorption, desorption, and surface diffusion may result in the formation of nontrivial surface morphologies. X-ray photon correlation spectroscopy opens up new possibilities for understanding these processes. In this work, we perform in situ x-ray experiments in grazing incidence geometry to follow the growth of diindenoperylene thin films in real time, revealing details of the dynamics during molecular island formation. Comparison with simulations allows to extract dynamic and kinetic time scales. We observe time scales in the range of a few hundred seconds which occur mainly due to kinetics, i.e. island growth. Importantly, we can relate the observed heterogeneous behavior in dynamics to the number of open layers, revealing information about the change in the roughness, and the growth speed of each layer.

Keywords

• coherent x-ray scattering
• thin film growth
• structure formation
• dynamical heterogeneity