In recent years a lot of effort has been put into resolving the microscopic properties of oxidation [1, 2]. In spite of above the cost of unwanted oxidation, corrosion, in industrial countries is about 2-3% of their gross national product per year [3] and the basic atomic level knowledge of metal oxidation is still missing. One approach to control the metal surface oxidation is to atomically modify metal surface with dopants. The surface structure in the early stage of surface oxidation critically affects the properties of oxide nanostructures.
In this study the initial oxidation of Cu(100)-c(10×2)Ag and Cu(100)-c(2×2)N surfaces have been characterized by using surface sensitive low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES) techniques. Atomic nitrogen nano islands has been created on Cu(100) by bombarding the surface with nitrogen ions [4]. Correspondingly atomic silver layer has been generated on Cu(100) by resistively heated evaporator [5]. Depending on the amount of silver and nitrogen pre-coverages on Cu(100) it is possible to influence oxygen uptake dramatically.
AES and LEED measurements suggested that when pre-coverages are in the sub-saturation (< 0.5 ML for N and < 0.9 ML for Ag) regime oxygen molecules adsorb dissosiatively on bare copper areas on Cu(100). No nitrogen segregation or nitrogen desorption are observed when oxygen background exposures are given at 300 K. In the case of silver pre-coverages the situation is something else. A strong decline in AES signal ratio (AgMNN / CuLMM) and new features in LEED patterns indicated very intensive oxygen adsorption induced copper segregation to the surface.
[1] M.P. Ryan, D.E. Williams, R.J. Chater, B.M. Hutton and D.S. McPhail, Nature 415 (2002) 770.
[2] H. Over and A.P. Seitsonen, Science 297 (2002) 2003.
[3] P. Marcus, Electrochimica Acta 43 (1-2) (1998) 109.
[4] S.M. Driver and D.P. Woodruff, Surface Science 492 (2001) 11.
[5] P.T. Sprunger, E. Lægsgaard and F. Besenbacher, Physical Review B 54 (11) (1996) 8163. |