An Aes and Leed Study of Carbon and Oxygen Sorption on Copper Surfaces

In cleaning copper surfaces by ion bombardment and annealing, carbon appears very often as a final contaminant which is very difficult to eliminate totally compared with other contaminants (0, S, Cl). Even during ion bombardment, surfaces are easily contaminated by carbon and the degree of contamination depends on the cleaning conditions. The main cause of the contamination may be the decomposition of hydrocarbons of the residual gas [1,2]. In spite of this frequently occurring contamination by carbon, to our knowledge systematic studies of carbon on copper surfaces have not been published. Only a LEED observation of a carbon superstructure on Cu(100) [2] and a metal deposition study on Cu (1 00), contaminated by carbon [3] have been reported. In this paper we present results of a LEED—AES study on Cu(1 11) and Cu(l 10), both at different carbon coverages. To estimate the carbon coverage the co-adsorption of oxygen on Cu(1 10) covered by carbon was also studied. In contrast with carbon, the adsorption of oxygen on copper surfaces has been extensively studied by many authors using various surface analytical techniques, such as LEED, AES, XPS, UPS, ELS, ellipsometry and work function measurements. For recent reviews cf. refs. [4,51. In this paper additional data on the adsorption of oxygen on Cu(1 10), obtained by LEED and AES, are reported.