Observation of structure sensitive decomposition of Cp(allyl)Pd on Pd nanodots formed by MO-CVD
A. Binder, M. Seipenbusch, G. Kasper
Chemical Vapor Deposition, 2011, 17 (1-3), 54-57
The decomposition kinetics of the organometalic precursor Cyclopentadienyl-allyl-Pd [Cp(allyl)Pd] on silica and titania substrates (as well as previously deposited Pd) were investigated by continuous MO-CVD at atmospheric pressure. The substrate particles were freshly generated in an aerosol process with well defined and known densities of surface OH-groups and then coated immediately in a second reactor. Time-resolved data on size and number density of deposited Pd nano-dots on the carrier particles were ob-tained by electron microscopy and used as a means to infer the decomposition kinetics. It was found that decomposition proceeded very rapidly for a few seconds, both by pro-ton initiated decomposition on surface OH-groups and by autocatalysis, until the Pd nano-dots had grown to a size of about 2 nm, where autocatalysis came to a standstill, regardless of precursor concentration, residence time in the CVD reactor, or decomposi-tion temperature. Proton initiated decomposition on OH-groups continued to depend measurably on these process parameters in terms of the number density of Pd dots, even after autocatalysis had stopped. Our observations indicate that autocatalysis is structure sensitive.