C60 molecules grown on a Si-supported nanoporous supramolecular network: a DFT study

Abstract

C₆₀ fullerene assemblies on surfaces have attracted considerable attention because of their remarkable electronic properties. Now because of the competition between the molecules–substrate and the molecule–molecule interactions, an ordered C₆₀ array is rather difficult to obtain on silicon surfaces. Here we present density functional theory simulations on C₆₀ molecules deposited on a TBB (1,3,5-tri(1′-bromophenyl)benzene) monolayer lying on the Si(111)–boron surface (denoted SiB). The C₆₀ molecules are located in the nanopores formed by the TBB network. Adsorption energy calculations show that the SiB surface governs the C₆₀ vertical position, whereas the TBB network imposes the C₆₀ lateral position, and stabilizes the molecule as well. The low charge density between the C₆₀ and the SiB substrate on one hand, and on the other hand between the C₆₀ and the TBB molecules, indicates that no covalent bond is formed between the C₆₀ and its environment. However, according to charge density differences, a drastic charge reorganisation takes place between the Si adatoms and the C₆₀ molecule, but also between the C₆₀ and the surrounding TBB molecules. Finally, calculations show that a C₆₀ array sandwiched between two TBB molecular layers is stable, which opens up the way to the growth of 3D supramolecular networks.