Towards an understanding of the behavior of silanes on glass: an atomistic simulation study of glass surfaces

The present work attempts to develop a better understanding of the glass substrates upon which silane molecules are deposited. Experimentally, when a sodium silicate substrate is used, the silane layer does not bind as well compared to an alkaline earth borosilicate glass (AEBS). Molecular dynamics simulated annealing procedures were used to create atomistic models of these glasses and their surfaces. In sodium silicate glass, we see segregation of sodium ions to the surface and formation of sodium-rich regions. For the AEBS glass, we see a more homogenous distribution of ions. Boron, aluminium, silicon and oxygen form a connected framework structure. The barium and calcium ions are distributed throughout the structure and show no evidence of segregation. We speculate the poor performance of sodium silicate, compared to the AEBS, as a silane substrate could be attributed to its compositionally inhomogeneous surface.