A STM study on temperature-dependent adsorption of H$_2$O on Si(001)

We studied the temperature dependence of water molecule adsorption on the Si(001)-2$\times$1 surface by using Scanning Tunneling Microscopy. The water molecules are known to dissociate during the adsorption on Si(001)and form Si-H and Si- OH bonds. Recently, we demonstrated that they are two adsorption configurations: ID (inter-dimer) and OD (on-dimer). These two configurations show population ratio of n(ID)/n(OD) $\sim$ 5 at Room Temperature. In order to understand the adsorption kinetics more thoroughly, we have measured n(ID)/n(OD) by varying the sample temperature from 300K to 870K. It is found that n(ID)/n(OD) show strong temperature dependence, and it even becomes smaller than 1. The cross-over temperature is at around 470K.