THE STICKING COEFFICIENT OF PD ON PLANAR ALUMINA SUPPORTS

Accurate sticking coefficient measurements of Pd on amorphous and single-crystal alumina supports as a function of metal exposure and support temperature are reported. Emphasis is placed on small metal exposures and some elevated temperatures, which are needed for preparing very small, spatially separated, and thermally stable supported Pd particles. A combination of AES, electron probe X-ray measurements, TEM, and Auger modelling was used to determine sticking coefficients for metal exposures between 0.1 and 1.5 monolayers (ML), at support temperatures ranging from room temperature to 850 K, and for deposition rates of 0.87, 0.74 and 0.13 ML min-1. For elevated temperatures and small metal exposures, the sticking coefficient was found to deviate substantially from unity and can be as low as 0.50 to 0.60. © 1990 Pergamon Press plc.