Adsorption characteristics of F and Cl atoms on fused silica surface defects

F and Cl atoms are always brought by the process of wet etching for fused silica devices, which dramatically influence the performance of the devices. The adsorption characteristics of F and Cl atoms with two main fused silica surface defects (E', NBOHC) were investigated on the basis of first-principle methods. Through the comparison of absorption capacity of different surface defects, we found that E' has larger capability to adsorb halogen atoms than NBOHC, and F atom is easier to be trapped by surface defects than Cl atom. Furthermore, the electronic structure and the bonding nature for surface defects are also studied and the calculations show that the introduction of F and Cl atoms will lead to the disappearing of defect states in band gap. And this adsorption process of F and Cl atoms on fused silica surface can be considered to chemical adsorption.