Structural, chemical, and electronic properties of Cu/Ta(110)

The properties of ultrathin Cu fils on a Ta(110) substrate have been studied using X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), temperature-programmed desorption (TPD), and infrared reflection adsorption spectroscopy (IRAS). For coverages of < 1.2 monolayer the Cu overlayers grow pseudomorphic with respect to the Ta substrate. XPS results indicate that the Cu(2p sub 3/2 ) binding energy of the supported Cu atoms is perturbed by +0.3 eV compared to that of the surface atoms in Cu(100). These electronic and physical perturbations induce distinct differences in the chemisorptive properties of the Cu films. This is evidenced by CO TPD results which indicate a 50K increase in the carbon monoxide desorption temperature as well as a CO stretching frequency that is 20 cm exp --1 higher than observed for the Cu(111) surface. A comparison of these results with those previously obtained for Cu overlayers on different substrates shows a correlation among the electronic perturbations of the adlayers, the metal--substrate bond strengths, the CO desorption temperatures, and the C--O stretching frequencies.