Surface modification of silica with ultraviolet laser radiation

A frequency-doubled copper vapour laser was used to irradiate the surface o f silica with ultraviolet light at fluences of between 0.1 and 0.5 J/cm(2) per pulse for several hundred pulses. Analysis of the surface composition u sing time-of-flight secondary-ion mass spectroscopy (TOF-SIMS) shows that t he relative surface-hydroxyl (OW) concentration decreases with increasing l aser irradiance. This dehydroxylation results: in silica surfaces with fina l-state hydroxyl concentrations similar to those obtained through the therm al treatment of silica at around 1000 degreesC. The mechanism for the dehyd roxylation reported here, however, is more likely to be photolytic than tht r-mal. Laser dehydroxylation allows fur the selective and rapid dt hydroxyl ation of silica offering many practical advantages over thermal dehydroxyla tion. The modified surface has significantly increased hydrophobicity compa red to the untreated silica surface.