New evidence for multiple binding sites for sulfur at the Ni(100)-vacuum interface

✍ Scribed by S.P. Weeks; E.W. Plummer

• Book ID: 103015647
• Publisher: Elsevier Science
• Year: 1977
• Tongue: English
• Weight: 263 KB
• Volume: 48
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(77)85103-8

✦ Synopsis

Measurements of adsorbate-derived peaks in angle-resolved photoemission energy distr~utions may provide a useful method for the study of bulk/surface diffusion of contaminants in metals. Energy distr~utions for c (2 × 2) sulfur on lqi(100) at 50* (± 4 °) t~allection angle along (001) for fit,.) --21.2 eV (Hel) are characterized by a single sulfur-derived peat: at 4.5 eV binding energy, belkved to be due to sulfur in the four*fold hollow surfa6e site determined by LEED. Further sulfur dosage or excessive heating results in the appearance of a second peak in the spectrum, at 1.25 eV higher binding energy, while maintaining a sharp c(2 x 2) LEED structure. The new binding configuration indicated by '_he second sulfur peak is interpreted as the penetration of sulfur into the substrate. This interpretation is supported by further studies of the dependence of the higher binding energy peak on temperature and dosage. This method of observing bulk-surface diffusion should be applicable to many other adsorbate/~ubstrate systems, as long as the adsorbate-derived peak can be observed and identified.