Rh atom ejection from keV ion-bombarded p(2 x 2)O/Rh/111/: Adsorption site and coverage determination from angle-resolved desorption measurements

Journal Article · Wed Feb 01 04:00:00 EST 1989 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.456045· OSTI ID:6533336

Reimann, C T; El-Maazawi, M; Walzl, K; Garrison, B J; Winograd, N; Deaven, D M

Angular distributions of Rh atoms desorbed by energetic ion bombardment of an oxygen covered Rh/111/ surface are measured accurately using a multiphoton resonance ionization (MPRI) detection technique. The results, in conjunction with molecular dynamics calculations of the ion impact event show that these distributions reflect the near-surface crystal structure. The molecular dynamics calculations were performed using a many-body embedded-atom potential to describe the dynamics of the Rh atoms and a pair-wise additive potential to describe the oxygen--Rh interactions. Several oxygen overlayer structures were considered for molecular dynamics modeling of the desorption process, including p(2 x 2) overlayers with a coverage of 0.25 monolayer (ML), and p(2 x 1) overlayers with a coverage of 0.50 ML, both of which are consistent with low energy electron diffraction (LEED) data. Three different adsorption sites were tested: threefold symmetric sites over second layer Rh atoms, threefold symmetric sites over third layer Rh atoms, and atop sites. The calculated azimuthal angular distributions of desorbed Rh atoms for each of these cases are unique, matching the experimental data best in the case of a p(2 x 1) overlayer with oxygen atoms adsorbed in threefold symmetric sites over third layer Rh atoms. The calculated Rh atom desorption yield (ejected atoms per incident ion) is sensitive to the oxygen coverage in the range 0.25--0.50 ML. These calculations are important in developing a surface bonding site and coverage consistent with LEED and our experiments. The peak in energy distribution of ejected Rh atoms from the oxygen covered surface is at a lower energy value than that of the clean metal.

• Research Organization: Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
• OSTI ID: 6533336
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 90:3; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

656003* -- Condensed Matter Physics-- Interactions between Beams & Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ADSORPTION
ANGULAR DISTRIBUTION
BEAMS
COLLISIONS
DESORPTION
DISTRIBUTION
ELEMENTS
ENERGY RANGE
ION BEAMS
ION COLLISIONS
KEV RANGE
METALS
NONMETALS
OXYGEN
PLATINUM METALS
RHODIUM
SORPTION
STRUCTURE FACTORS
SURFACE PROPERTIES
TRANSITION ELEMENTS