Selective nucleation and area-selective OMCVD of gold on patterned self-assembled organic monolayers studied by AFM and XPS: A comparison of OMCVD and PVD

We demonstrate the area selective organometallic chemical vapor deposition (OMCVD) of ultrathin gold layers, using (trimethylphosphine)methylgold [(CH₃)₃P]AuCH₃ as the gold source, onto self-assembled monolayers (SAMs) of ω-functionalized, long chain alkanethiols on gold and silver coated silicon and mica samples. The dependence on the reaction time of surface coverage with gold nano-clusters is analyzed by atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) shows that nucleation and growth occur only on thiol functionalized surfaces and not on methyl or hydroxyl functionalized SAMs. The selectivity of the growth is completely lost if gold is deposited by thermal evaporation of the pure metal, as shown in direct comparison with the OMCVD method employing mixed SAMs of different surface reactivity (-SH vs. -CH₃) that were patterned by microcontact printing.