| AVS 55th International Symposium & Exhibition | |
| Surface Science | Wednesday Sessions |
| Session SS2+NC-WeM |
| Session: | Functional Metal Oxides and Quantum Metal Structures |
| Presenter: | W. Kim, Korea Research Institute of Standards and Science |
| Authors: | W. Kim, Korea Research Institute of Standards and Science I. Kim, Chonnam National University, Republic of Korea C. Min, Seoul National University, Republic of Korea H.-D. Kim, Pohang Accelarator Laboratory, Republic of Korea C. Hwang, Korea Research Institute of Standards and Science |
| Correspondent: | Click to Email |
The formation of quantum well states in metallic thin films under a certain boundary condition cause the sharp change in the intensity of electron density of states(DOS) at Fermi level of the thin films as the film thickness varies. This thickness dependence of DOS at Fermi level is the origin of quantum size effects found in many physical properties of the metallic thin films. In this study, we carried out the experiments to examine the effect of the quantum well states in the Cu/fcc Co(001) system on the formation of a surface alloy. It is well known that deposition of a half monolayer Mn on the Cu(001) leads to the formation of a very stable single layer MnCu c(2x2) surface alloy, and the origin of this process has been attributed to the magnetic energy of enhanced surface magnetic moment of Mn atom.1 As the first step of the experiment, we examined the evolution of the Mn core level photoemission spectra with increasing Mn thicknesses, comparing the low energy electron diffraction(LEED) pattern for each Mn thickness. From the obtained spectra. we found out that there exist the features which are closely related to the surface alloy formation. Based on this spectroscopic evidence of surface alloying, we investigated the effect of quantum well states on the formation MnCu surface alloying. We deposited half monolayer Mn atoms on the wedge shaped Cu layers formed on the fcc Co(001) surface, and measured Mn core level photoemission spectra for the different Cu thicknesses. The observed spectra show overall correlation with the oscillating behavior of DOS at Fermi level as the thickness of Cu layers changed. Judging from the changes of Mn core level spectra, we could conclude that the lower electron density of states at Fermi level enhanced the formation of MnCu ordered surface alloy. This conclusion was also confirmed by the direct observation of the intensity of the half order spots of c(2x2) LEED pattern of MnCu surface alloy formed on the Cu/fcc Co(001) system with selected thicknesses of Cu layer. The results of our study strongly support the previous interpretation of the formation of stablized MnCu surface alloy.
1. M. Wuttig et al., Phys. Rev. Lett. 70, 3619 (1993).