Water adsorption on native and hydrogenated diamond (001) surfaces

Understanding water interaction with diamond surfaces is fundamental for applications in tribology, device technology, and microelectronics operating in biological environments. In this paper, we provide a full microscopic description of the interaction of water with diamond (001) surfaces. We performed ab initio calculations within the framework of density functional theory including long-range van der Waals interactions. We considered both native and hydrogenated surfaces. We calculated the structure and the energetics for molecular and dissoiative adsorption, and in the case of exothermic proesses, we determined the energy barriers for dissoiation. Our results allow prediction of the formation of water islands on native surfaces that grow along and perpendicularly to dimer rows. Moreover, they highlight the role played by the water coverage in determining the adsorption mode (physisorption or dissoiation), suggesting an explanation for experimental results on similar Si(001) surfaces. Finally, we provide an understanding on the mechanism of carbon dangling bond passivation by water which is the key factor in determining the excellent tribological performances of diamond in humid environments as measured in experiments. © 2010 American Chemical Society.