18 research outputs found
Electromigration-Induced Flow of Islands and Voids on the Cu(001) Surface
Electromigration-induced flow of islands and voids on the Cu(001) surface is
studied at the atomic scale. The basic drift mechanisms are identified using a
complete set of energy barriers for adatom hopping on the Cu(001) surface,
combined with kinetic Monte Carlo simulations. The energy barriers are
calculated by the embedded atom method, and parameterized using a simple model.
The dependence of the flow on the temperature, the size of the clusters, and
the strength of the applied field is obtained. For both islands and voids it is
found that edge diffusion is the dominant mass-transport mechanism. The rate
limiting steps are identified. For both islands and voids they involve
detachment of atoms from corners into the adjacent edge. The energy barriers
for these moves are found to be in good agreement with the activation energy
for island/void drift obtained from Arrhenius analysis of the simulation
results. The relevance of the results to other FCC(001) metal surfaces and
their experimental implications are discussed.Comment: 9 pages, 13 ps figure
Surface characterization of catalytically active metal, alloy, and compound films. Progress report, September 1, 1978--August 31, 1979. [Ag--Cu, Pd--Cu, Pt--Au]
Characterization of several catalytically active metal expitaxial systems was carried out. In addition to the Ag/Cu system previously reported, TEM, RHEED, and AES studies were carried out on the Pd/Cu system. Studies were also made on the Pt/Au system. Pd grows on Cu by a monolayer growth mechanism with misfit dislocations at the interface. The thinnest Pd layers are highly strained in compression. As the overgrowth thickens, the strain decreases rapidly so that very little remains after 3 monoatomic layers have formed. The Auger line profile from a strained Pd monolayer in intimate contact with a Cu substrate is different from what one gets from bulk Pd suggesting that a line profile analysis of the AES spectra from monolayer epitaxial films may be useful in determining the modified electronic structure resulting from the Pd/Cu interaction. The results obtained so far were carried out with a UHV-RHEED system built 12 years ago. Because of the almost continuous useage of this system on the Pd/Cu studies, little time was available for studying other potentially usefuel systems, such as those involving Pt. The recent availability of a LEED instrument, a new and more flexible stainless steel UHV system, was constructed. This system is almost finished. It will allow the simultaneous investigation of two catalytic systems, given much needed flexibility