Researchers from Humboldt-Universität zu Berlin, Universität Tübingen, Deutsches Elektronen-Synchrotron (DESY) and Technische Universität Berlin have observed the self-arrangement of football-shaped carbon molecules into ultra-smooth layers, in real-time, using the PETRA III ultrabright X-ray source at DESY. This study provides insight into basics of the growth process that takes place in buckyballs.
Spherical molecules that are made of 60 carbon atoms (C60) with alternating hexagon and pentagon structure are called as buckminsterfullerenes or “buckyballs.” Richard Buckminster Fuller, an American architect, designed geodesic domes and the C60 spherical molecules resemble these domes. Hence, they were named as buckminsterfullerenes.
The researchers studied the manner in which buckyballs settled on molecular vapour substrates. They observed that the carbon molecules grew in islands, in layers one after another, while being just a molecule in height. Tower-like structures were not formed. Before even 1% of the second carbon molecule layer was formed, 99% of the first layer was completed, and this led to formation of extremely smooth layers. A single layer was found to take about a minute to grow, and the surfaces had to be measured within this duration. The DESY PETRA III X-ray source enabled real-time observation of the growth process.
In order to understand the evolution of the surface morphology at the molecular level, we carried out extensive simulations in a non-equilibrium system. These describe the entire growth process of C60 molecules into a lattice structure.
Kleppmann, PhD student
The research team performed simulations in a non-equilibrium system to study molecular level surface morphology evolution of the system. Three major energy parameters for the system were determined simultaneously. They were - the “diffusion barrier,” the Ehrlich-Schwoebel barrier and the binding energy that exists between fullerene molecules. When a molecule lands on an island it has to overcome the Ehrlich-Schwoebel barrier to hop down, and if it needs to travel on the surface then it has to overcome the diffusion barrier.
The insights gained from this study will enable researchers to tune the nanostructures from carbon molecules for applications in plastic electronics and in organic solar cells that contain C60.
The researchers have published this study titled "Unravelling the multilayer growth of the fullerene C60 in real-time" in Nature Communications journal.