Vapour phase formation of amino functionalised Si_3N_4 surfaces

摘要

Self-assembled monolayer (SAM) formation of silanes on SiO_2 surfaces has been extensively studied. However, SAMs formed on silicon nitride (Si_3N_4) substrates have not been explored to the same level as SiO_2. even though they are of technological interest with a view to the chemical modification of micro-electromechanical systems (MEMS). Therefore, this article presents the formation and characterisation of 3-aminopropyltrimethoxysilane (APTMS) SAMs on Si_3N_4 substrates from solution phase and vapour phase, compared to the well characterised APTMS SAMs formed on SiO_2 surfaces. Contact angle, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and ellipsometric data indicate the formation of APTMS SAMs (0.55 nm ellipsometric thickness) after 60 min immersion of either SiO_2 or Si_3N_4 substrates in APTMS solution (0.5 mM in EtOH). By comparison Si_3N_4 substrates exposed to APTMS vapour, at 168 mbar for 60 min, result in the formation of the equivalent of a bi or trilayer of APTMS.