Sur f ace Science 157 (1985) 327-338 North-Holland, Amsterdam 321 STRUCTURAL SPECIFICITY OF DISSOCIATIVE CHEMISORI’TION OF OXYGEN FROM MOLECULAR OXYGEN AND FROM NITROUS OXIDE ON COPPER SURFACES J.S. ARLOW and D.P. WOODRUFF Physics Department. University of Wunwck, Coventry CV4 7AL, UK Received 17 December 1984; accepted for publication 20 February 1985 Auger electron spectroscopy of cylindrical copper surfaces has been used to study the relative reactivity of surfaces in the (110) zone to the dissociation of 0, and N,O at room temperature. Strong structural sensitivity is seen in both reactions with the atomically “rough” (110) and (311) faces being most reactive while the atomically “smooth (100) and (111) faces are least reactive. The reactivity of intermediate faces is understood in terms of the step density or the proportion of “rough” surface, although there is also clear evidence for diffusion of dissociated oxygen away from steps over (111) terraces which leads to an enhanced reactivity of (111) vicinals. In the case of N,O dissociation there is evidence that (110) is especially reactive relative to its vicinals, and relative to (3111, indicating a non-linearity in dependence of reactivity on step density at high densities which is not seen for the dissociation of 0,. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQP 1. Introduction Many adsorption processes and reactions at surfaces are known to be sensitive to the local structure of the surface and while comparisons of the activity of the major low index faces of materials are common, there is growing interest in studying intermediate vicinal surfaces. In two previous studies of oxygen chemisorption on copper [l] and the initial stages of oxidation of nickel [2], we have shown that a study of the adsorbate coverage on the surface of a cylindrical single crystal sample as a function of exposure, using Auger electron spectroscopy, provides a valuable method of establishing the relative activities of a wide variety of such orientations. Other workers have also demonstrated the possibility of monitoring other aspects of the adsorption properties of cylindrical surfaces using work function measurements [3], photo- emission [4] and electron diffraction [5] as well as Auger electron spectroscopy zyxwvutsrqp 161. In this paper we present the results of new measurements on the rate of formation of chemisorbed oxygen on copper surfaces in the (110) zone from both molecular oxygen and from nitrous oxide. The data have been obtained using an improved method of collecting and analysing the Auger electron 0039-6028/85/$03.30 0 Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)