Molecular modeling of water diffusion in amorphous SiC

The diffusion of water in amorphous SiC (a-SiC) was investigated by molecular modeling methods based on density functional theory. It was assumed that the structure of a-SiC at the molecular level can be described by a model that takes into account a distribution of cage structures which consist of SiC units forming n-member rings from a suitable precursor in a chemical vapor deposition process. Electronic structure calculations are then performed to determine the energy barrier that the water molecule encounters when it penetrates through SiC rings of various sizes. It has been found that along its diffusion path through the SiC network the water molecule neither breaks up nor attaches itself to the SiC network and the energy barrier for diffusion depends mainly on the local SiC ring topology.