Abstract
High resolution electron energy loss spectroscopy (EELS) and angle-resolved ultra-violet photoelectron spectroscopy (UPS) have been used: (1) to study a surface phonon of Cu(110) as a function of oxygen coverage, (2) to identify oxygen adsorption site(s) in the p(2×1)O, c(6×2)O, and disordered oxygen overlayer (formed by O2 exposure at 100 K), and (3) to determine whether molecular adsorption or dissociation of O2 followed by atomic adsorption occurs after oxygen exposure at 100 K. With EELS, a continuous shift in energy of the surface phonon as a function of oxygen exposure at 300 K is observed. Our EELS data for the p(2×1)O overlayer support previous reports of a single long-bridge adsorption site, while indicating two sites are populated in the c(6×2)O overlayer: a long-bridge site and a four-coordinated site. The long-bridge site is populated at all coverages while the four-coordinated sites is occupied only after high exposures (≥2×104 L) at room temperature, or after exposures >2 L at low temperature (100 K). For both conditions the oxygen coverages are greater than 0.5 monolayer. Also, EELS and complementary UPS data clearly show that oxygen adsorbs dissociatively on Cu(110) after O2 exposure at 100 K. At this temperature, LEED results indicate that the oxygen atoms are adsorbed without long-range order; however, local adsorption sites, which are similar to those in the c(6×2)O surface, are observed.
| Original language | English |
|---|---|
| Pages (from-to) | 15-31 |
| Number of pages | 17 |
| Journal | Surface Science |
| Volume | 188 |
| Issue number | 1-2 |
| DOIs | |
| State | Published - Sep 2 1987 |
| Externally published | Yes |
Funding
The authors acknowledge support from NSF under grant DMR 81-09261 and from DOE under contract DE-AC05-840R21400 with Martin Marietta Energy System, Inc. We also thank the staff of the Tantalus-I storage ring for their excellent support and Drs. G.R. Gruzalski and N.J. Di Nardo for many insightful discussions.