Heterogeneity in the surface structure of a Cu{100}-c(2×2)-Pd surface alloy

✍ Scribed by M. Valden; J. Aaltonen; M. Pessa; M. Gleeson; C.J. Barnes

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 819 KB
• Volume: 228
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(94)01007-2

✦ Synopsis

The structure and compositional profile of a Cu{ lOO}-c( 2 x 2)-Pd surface alloy formed by deposition of 0.55 f 0.1 ML of Pd on Cu{ 100) at 300 K has been examined by a range of surface sensitive techniques and is shown to be highly heterogeneous. Using CO as a probe molecule, thermal desorption spectroscopy demonstrates that a significant fraction ( c 40%) of the outermost layer is pure Cu. X-ray photo-electron polar intensity plots along the [ 0 lo] azimuth reveal a zeroth-order diffraction peak at a polar emission angle of 40"-45' indicating significant penetration of Pd beyond the outermost Cu layer. Absence of a strong 0" forward scattering peak limits the compositional profile to one in which the majority of sub-surface Pd is located within the second layer. Model single scattering cluster calculations confirm this and indicate a local expansion of the outermost interlayer spacing of 0.4 f 0.2 A in regions of high local Pd concentration.