Water-induced negative electron affinity on diamond (100)

The interaction of water vapor on clean diamond (100) has been studied using ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy (XPS), X-ray-absorption near-edge structure (XANES) spectroscopy, and high-resolution electron energy loss spectroscopy (HREELS). It is shown that water dissociates at room temperature on clean diamond formin g C-H and C-OH bonds, resulting in a surface dipole layer which produces the condition of negative electron affinity (NEA). The strong polarization dependence of the O K XANES could be associated with the out-of-plane orientation of the OH bonds. Density functional theory (DFT) calculations confirm the existence of NEA on this surface with a mixture of hydrogen and hydroxyl (OH) terminations.