Surface alloying of a Co film on the Cu(001) surface

Surface alloying during the growth of ultrathin Co film on Cu(001) surface was studied by employing Xe as a probing atom. Work functions and Xe 5p spe ctra for the clean Cu(001) surface and Co films deposited on the Cu(001) su rface, both at room temperature and around 50 K, were taken as a function o f Xe dosage. The pure Co film, represented by a thick Co film deposited on the Cu(001) surface at 50 K, showed little change of work function as the d osage of Xe increased. In contrast, a Linear decrease of work function was observed on the Cu(001) surface as Xe coverage increased. The binding energ y of the Xe 5p spectra on a Co film showed a shift toward higher binding en ergy with increasing Xe coverage, while that on clean Cu(001) surface is al most constant before completion of one Xe monolayer (ML). These two distinc tive characteristics were taken as fingerprints of Co and Cu exposed surfac es, respectively. Then, a nominal 2 ML Co film was deposited on Cu(001) sur face at room temperature and examined by the fingerprints. It is estimated that about 65% of the surface is made up of disordered Co-Cu alloy, while t he rest of the surface is made up of Co atoms. (C) 2000 Elsevier Science B. V. All rights reserved.