New insights into plasma-assisted dissociation of organometallic vapors for gas-phase synthesis of metal nanoparticles

Organometallic compounds are a general class of metal precursors that are used for chemical vapor deposition of metal films and nanoparticle nucleation in the gas phase. While there have been numerous studies of metal film deposition, there exist far fewer studies of how organometallic vapors are dissociated in the gas phase to homogeneously nucleate metal nanoparticles, and, most importantly, if the organic components are incorporated in the nanoparticle material. Here, we study the dissociation of organometallic precursors in an atmospheric-pressure microplasma by optical emission spectroscopy and assess the chemical composition of the as-grown nanoparticles by X-ray photoelectron spectroscopy. We find that certain precursors such as Ni(Cp)₂ do not form carbon except at higher discharge powers where electron and gas heating are enhanced. In comparison, precursors such as Cu(acac)₂ dissociate to form carbon moieties even at low discharge currents. These results should help guide processes that are intended to produce high-purity metal nanoparticles.