Substrate-independent sulfur-activated dielectric and barrier-layer surfaces to promote the chemisorption of highly polarizable metallorganics
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A novel plasma-based process has been invented in which sulfur is used to enhance the chemisorption of highly polarizable metallorganics to dielectric or barrier-layer surfaces. Three fundamentally different substrates were investigated: metal oxides (air-exposed Ta and SiO2), a hybrid dielectric (Trikon) and a polymeric material (SiLK). All the surfaces could be modified with relative ease, resulting in a substrate-independent process. Further, palladium (II) hexafluoroacetyl- acetonate was dosed on the substrates under study at sublimation and substrate temperatures of 34.8 °C and 175 °C. Results show that increased rf power and decreased system pressure during sulfur deposition result in a larger relative percent reduced sulfur, at for example, the SiO2 surface. In turn, this results in more palladium chemisorbed to the surface from a larger Pd 3d/Si 2p ratio. Rutherford backscattering spectrometry was used to estimate a sulfur areal density of approximately 1×1015 atoms/cm2 on air-exposed Ta, when sulfur was deposited via H2S and He in the range of 300 W to 700 W rf power at 60 mTorr. It was shown that the sulfur-activated surfaces are stable under ambient conditions. Also, after the sulfur-activated SiO2 surface was dosed with PdII(hfac)2, the S 2p X-ray photoelectron spectroscopy spectrum shifts from 163.7 eV (before dosing) to 162.8 eV (after dosing), which gives evidence of Pd-S interfacial bonding.
KeywordsPalladium Metal Oxide Chemisorption Interfacial Bonding Areal Density
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