Chemical state and wettability of ion-irradiated diamond surfaces

It is shown that the wettability of diamond can be tailored in a broad range by the surface modification via ion bombardment. The polished MPCVD diamond films were oxidized in air at 550 °C to make the surface hydrophilic and then were irradiated with Ar+ ions at 1 keV energy at doses ranging from 1×1014 to 5×1016 cm−2. The surface state evolution was monitored in situ with X-ray photoelectron spectroscopy (XPS) and X-ray excited Auger electron spectroscopy (XAES). A progressive sp3 to sp2 bond transformation took place with the dose increase, while the irradiated surface becomes hydrophobic with the water contact angle increasing from 24° to 67° as measured with a sessile drop method. The heating of the ion-treated samples in air at 450 °C restores the hydrophilic properties inherent to oxidized diamond surface.