Atomic Control of Water Interaction with Biocompatible Surfaces: The Case of SiC(001)

The interaction of water with Si- and C- terminated $\beta \mathrm{\text{−}}\mathrm{S}\mathrm{i}\mathrm{C}\left(001\right)$ surfaces was investigated by means of ab initio molecular dynamics simulations. Irrespective of coverage, varied from $1/4$ to 1 monolayer, we found that water dissociates on the Si-terminated surface, substantially modifying the clean surface reconstruction, while the C-terminated surface is nonreactive and hydrophobic. Based on our results, we propose that STM images and photoemission experiments may detect specific changes induced by water on both the structural and electronic properties of SiC(001) surfaces.

Figure 1

Dissociated water configurations on the Si-terminated SiC(001) surface. Schematic side view of dissociation geometries of one water molecule on Si-SiC(001): dark (light) grey spheres in the substrate represent C (Si) atoms, while dark (light) grey spheres in the adsorbate represent O (H) atoms. Only the three outermost slab layers are indicated.

Figure 2

Computed filled state STM images of the Si-terminated SiC(001) surface after water exposure. The most favorable $1/4$ (left) and 1 ML (right) configurations for water on the Si-SiC(001) surface as obtained with a tip voltage of $-1.5\mathrm{V}$. The geometry of the last two surface layers and that of the dissociated -H and -OH fragments are projected on the image to identify the surface geometric structure.

Figure 3

Dissociation mechanism of water on the Si-terminated SiC(001) surface at high coverage. Two successive snapshots of the dissociation process at 1ML water coverage on Si-SiC(001). Only the two molecules involved in proton exchange during this time interval are represented and labelled as 1 and 2. Colors as in Fig. 1. Only the three outermost slab layers are indicated.