Control wettability of the hydrogen-terminated diamond surface and the oxidized diamond surface using an atomic force microscope

The force-distance curve indicates the difference in wettability between the hydrogen-terminated (H-terminated) diamond surface and the AFM-field-assisted local oxidized (O-terminated) area. Using a hydrophilic (silicon with native oxide) tip and a hydrophobic (coated with gold) tip as AFM tips, the adhesion force mapping measurement shows that the H-terminated surface is hydrophobic and that the O-terminated surface is hydrophilic. After heating in vacuum, the difference in the adhesion force between two surfaces decreased. This means that water adsorbed on the tip and sample surfaces affects the adhesion force. As an alternative measurement, the contact angle measurement of the H-terminated surface and the chemically oxidized surface was performed. It is proved that the oxidized surface is more hydrophilic than the H-terminated surface and that its surface energy is derived from surface polarity such as that involved in hydrogen bonding and electric dipole which is twofold that the H-terminated surface.