Surface modification of Pt(111) by Sn adatoms: Evidence for the formation of ordered overlayers and surface alloys

• Published in: Surface science 1989-01, Vol.208 (1), p.34-54
• Main Authors: Paffett, M.T., Windham, R.G.
• Format: Article
• Language: English
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(89)90035-6

Vapor deposition of Sn onto Pt(111) in ultrahigh vacuum (UHV) has been examined by Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and low energy ion (Ne +) scattering spectroscopy (LEISS). The AES uptake plots for depositions at substrate temperatures between 140 and 400 K indicate a uniform layer growth up to a Sn exposure of 9.1 × 10 14 atoms cm -2. LEED data taken simultaneously indicate the successive appearance of the following patterns at submonolayer coverages: (√3 × √3) R30° followed by c(4 × 2). Simple overlayer real space structures are suggested for these ordered Sn overlayers. For Sn exposures greater than 9.1 × 10 14 atoms cm -2 at these substrate temperatures, nonlinear AES uptake plots and an increasingly diffuse LEED pattern are observed. For Sn depositions above 450 K, Pt-Sn alloy formation is strongly suggested from AES uptake plots and LEISS data. Annealing the Sn-Pt interface to 1000 K. produces ordered (as judged by LEED) alloy surfaces. Evidence for alloy formation is also inferred from variable incidence angle LEISS data. Real space models consistent with the data are proposed.