Experimental and theoretical studies of reaction and growth of ultrathin nickel and palladium films on aluminum single crystal surfaces.

摘要

Reaction and growth of ultrathin Ni and Pd films, deposited on Al(110) and Al(001) surfaces at room temperature were studied using high-energy ion scattering, x-ray photoelectron spectroscopy, and x-ray photoelectron diffraction. For Ni deposited on Al(110) surfaces, a strong Ni-Al reaction occurs at the Ni-Al interface. For the first two monolayers (ML) of deposited Ni, a NiAl-like compound is formed. The reaction continues with a different rate, forming a {dollar}rm Nisb3Al{dollar}-like compound for Ni coverages from 2 to 8 ML, at which point a Ni metal film begins to grow on the interface. However, Ni atoms deposited at {dollar}250spcircrm C{dollar} on the Al(110) surface, exhibit no surface compound formation, but diffuse 400 A deep into the Al bulk.; Interatomic potentials based on the embedded atom method are used in a Monte Carlo approach to simulate the evolution of the Ni-Al(110) interface as a function of Ni coverage. The calculated ion scattering yields and x-ray photoelectron intensities from Ni and Al atoms in these simulated interfaces are in good quantitative agreement with the experimental results. The ion scattering simulations show that a large amount of near-surface dechanneling occurs just below the Ni-Al(110) interface.; In contrast to the Al(110) room temperature results, Ni deposited on the Al(001) surface under the same experimental conditions results in the growth of metastable body-centered-cubic Ni at the interface up to 5 ML of Ni coverage in a Stranski-Krastanov growth fashion. After the bcc islands coalesce to cover the surface, a disordered Ni metal film covers the interface.; Ultrathin Pd films deposited on Al(001) surfaces exhibit strong reaction at the Pd-Al(001) interface. For the first 5 ML of deposited Pd, a PdAl-like compound is formed. After 5 ML of Pd coverage, a Pd metal film covers the reacted interface.