Deep-UV photochemistry and patterning of (aminoethylaminomethyl)phenethylsiloxane self-assembled monolayers

The 193 nm photochemistry of (aminoethylaminomethyl)phenethylsiloxane (PEDA) self-assembled monolayers (SAMs) under ambient conditions is described. The primary photodegradation pathways at low exposure doses (< 100 mJ cm(-2)) are benzylic C-N bond cleavage (ca. 68 %), with oxidation of the benzyl C to the aldehyde, and Si-C bond cleavage (ca. 32 %). Amine-containing photoproducts released from the SAM during exposure remain physisorbed on the surface, where they undergo secondary photolysis leading to their complete degradation and removal after ca. 1200 mJ cm(-2). NaCl (aq) post-exposure rinsing removes the physisorbed materials, showing that degradation of the original PEDA species (leaving Si-OH) is substantially complete after ca. 450 mJ cm(-2). Consequently, patterned, rinsed PEDA SAMs function as efficient templates for fabrication of high-resolution, negative-tone, electroless metal and DNA features with good selectivity at low dose (i.e., ca. 400 mJ cm(-2)) via materials grafting to the intact amines remaining in the unirradiated PEDA SAM regions.