Nano-fabrication of organosilane self-assembled monolayers: effects of proximity gap and irradiation time on photoreactivity and lamination

Organosilane self-assembled monolayers were photodegradated with VUV light of 172 nm in wavelength, using a VUV-exposure system whose proximity gap between photomask and substrate was filled with ambient air and adjustable at intervals of 1 m. The following knowledge of photodegradation processes was obtained: (1) a larger proximity gap was more favourable for promoting the photochemical reactions and advanced complete photodegradation of the monolayer; (2) such oxidized products as carboxyl groups appeared in irradiation time of several tens of seconds. Moreover, lamination of the second self-assembled monolayer (SAM) against the photodegradated SAM/Si substrate was conducted. It was possible for any permutation of SAMs to laminate the second SAM onto the SAM's surface photodegradated in activated oxygen atmosphere through the reaction between -COOH radicals and -OCH3 functional groups of organosilane precursors. Also, the conspicuous shift of XPS spectra was observed only in the case of laminating CMPhS-SAM on FAS/Si.