Low-energy electron-beam patterning of amine-functionalized self-assembled monolayers

Patterned amine-functionalized self-assembled monolayers have potential as a template for the deposition and patterning of a wide variety of materials on silicon surfaces, including biomolecules. Results are presented here for low-energy electron-beam patterning of 2-aminopropyltriethoxysilane and (aminoethylaminomethyl)phenethyltrimethoxysilane self-assembled monolayers on silicon substrates. On these ultrathin (1-2 nm) monolayers, lower electron beam energies (<5 keV) produce higher resolution patterns than high-energy beams. Auger electron spectroscopy indicates that low-energy electron exposure primarily damages the amine groups. At 1 keV, a dose of 40 μC/cm² is required to make the patterns observable by lateral force microscopy. Features as small as 80 nm were exposed at 2 keV on these monolayers. After exposure, palladium colloids and aldehyde- and protein-coated polystyrene fluorescent spheres adhered only to unexposed areas of the monolayers.