Wetting of thin layers of SiO2by water

摘要

We have measured the contact angle thgr; of water on silicon and on very thin layers of silicon dioxide grown on silicon. The silicon is hydrophobic and thgr; is near 90deg;. Oxides thicker than 30 Aring; are hydrophilic and thgr; is near 0deg;. For intermediate thicknesses, thgr; varies smoothly between these limits. Our results show that the interaction energy between water and the solid surface depends strongly on the oxide thickness. Consideration of different possible interactions leads us to conclude that this is due to corresponding changes in the structure or composition of the oxide surface.