Photoactivated Ru chemical vapor deposition using (η3-allyl)Ru(CO)3X (X = Cl, Br, I): From molecular adsorption to Ru thin film deposition

We have investigated photoassisted chemical vapor deposition (PACVD) of Ru on functionalized alkanethiolate self-assembled monolayers (SAMs) using (eta(3)-allyl)Ru(CO)(3)X (X = Cl, Br, I) precursors. Three SAMs were employed with -CH3, -OH, or -COOH terminal groups. Our data show that (eta(3)-allyl)Ru(CO)(3)Cl molecularly adsorbs on the functionalized SAMs and no Ru(0) is deposited in either the dark or under UV light. Similarly, (eta(3)-allyl)Ru(CO)(3)I molecularly adsorbs on all substrates studied. For (eta(3)-allyl)Ru(CO)(3)Br at longer deposition times under UV light, Ru(0) and RuOx are deposited on -CH3- and -OH-terminated SAMs. In contrast for -COOH-terminated SAMs, little or no Ru is deposited, which is attributed to the formation of Ru-carboxylate complexes that block further deposition. Density Functional Theory calculations show that the different deposition behaviors observed are not due to the primary photoprocess, which is the loss of a carbonyl ligand, but rather can be attributed to the energy required to lose a second carbonyl ligand, a secondary photoprocess. Together, these data suggest that PACVD can be employed for area selective deposition.

Automated summary

In this study, photoassisted chemical vapor deposition (PACVD) of Ru on functionalized alkanethiolate self-assembled monolayers (SAMs) was investigated. The different deposition behaviors observed on SAMs with different functional groups were attributed to the formation of Ru-carboxylate complexes that block further deposition. Density Functional Theory calculations showed that the primary photoprocess, loss of a carbonyl ligand, did not affect the deposition behavior significantly.