Micropatterning of self-assembled monolayers on silicon amplified with photochemically generated atomic oxygen

Vacuum ultraviolet (VUV) light of 172 nm in wavelength radiated from an excimer lamp has been applied to the photochemical micropatterning of an organic monolayer which was prepared from 1-hexadecanol and was covalently attached to a Si(1 1 1) surface with a SiOR form. Based on water contact angle measurements and X-ray photoelectron spectroscopy, it was shown that, with the VUV-irradiation in the presence of atmospheric oxygen, the hexadecyloxy monolayer was gradually decomposed and etched, followed by oxidation of the underlying Si substrate surface. Since, the VUV light simultaneously excites atmospheric oxygen molecules as well as the monolayer itself, atomic oxygen species are generated just on the monolayer surface. These photochemically generated oxygen atoms accelerate degradation and etching of the monolayer. By locally promoting this chemical amplification process with oxygen, namely, irradiating the monolayer surface thorough a photomask, the monolayer could be micropatterned. In addition, the patterned monolayer was successfully employed as a microtemplate for fabrication of microdimples on the Si substrate through chemical etching or that of organic microstructures through selective adsorption of organosilane molecules.