The Bonding of Organic Molecules on Silicon Carbide Monolayers with Si/C Vacancies

The physisorption and chemisorption of organic molecules on the defective silicon carbide monolayers were investigated using two-dimensional periodic models. Various monolayer types have been considered: hSiC (hexagonal configuration) and mSiC (Si atoms at all meta-positions of the six-membered rings). Structural defects introduced by removing the neutral Si and C atoms led to the local surface reconstruction and to the strong or weak intralayer interactions. Aminopropyltriethoxysilane, fluorosilatrane, methoxysilatrane and diaminotolan were compared as representative adsorbing molecules. Their interactions with defective silicon carbide monolayers were examined in terms of energetic stability, magnetic moments, spin-polarized electron density distribution, and bond-type analysis. The nature of the chemical bonding in the defective monolayers was analyzed using electronic descriptors such as phase-space Fisher information density that was derived within the framework of the orbital-free density functional theory. The nature of the O─Si/O…Si, N─Si/N…Si, and C─Si/C…Si bonds formed upon adsorption was elucidated, allowing weakly bound adsorption states to be distinguished from true chemisorption.