Excimer laser-assisted chemical process for formation of hydrophobic surface of Si (001)

Silicon (Si) wettability is one of the important parameters in the development of Si-based biosensing and lab-on-chip devices. We report on UV laser induced hydrophobicity of Si (001) wafers immersed in methanol during the irradiation with an ArF excimer laser. The irradiation with 800 pulses of the laser operating at 65 mJ/cm² allowed to significantly increase the hydrophobicity of investigated samples as characterized by the static contact angle change from 77° to 103°. Owing to the irradiation with relatively low laser fluence, no measurable change in surface morphology of the irradiated samples has been observed with atomic force microscopy measurements. The nature of the hydrophobic surface of investigated samples is consistent with X-ray photoelectron spectroscopy analysis that indicates formation of Si–O–CH₃ bonds on the surface of the laser-irradiated material.