Temperature effects on the coadsorption of K-CO on Ni(100)

High-resolution electron energy-loss spectra of the coadsorption of potassi um and CO on the Ni(100) surface show the role of temperature in driving ch emical species along the surface towards the formation of ordered islands m ade of alkali atoms and CO species. At low potassium precoverages, the form ation of K-CO islands occurs by heating the sample to 420 K. On the contrar y, for a potassium coverage near 0.38 ML, K-CO patches of ordered phases gr ow spontaneously even at 220 K. The interpretation of the present data reli es essentially on two literature works on the K-CO/Ni(100) system, one of t hem presenting calorimetric measurements and the other reporting the theore tical temperature behaviour of the chemical species on the nickel surface. (C) 2000 Elsevier Science B.V. All rights reserved.