| AVS 54th International Symposium | |
| Surface Science | Tuesday Sessions |
| Session SS-TuP |
| Session: | Surface Science Poster Session |
| Presenter: | Y. Takagi, RIKEN, SPring-8 Center, Japan |
| Authors: | Y. Takagi, RIKEN, SPring-8 Center, Japan K. Nakatsuji, University of Tokyo, Japan Y. Yoshimoto, University of Tokyo, Japan D. Sekiba, University of Tokyo, Japan Y. Harada, RIKEN, SPring-8 Center, Japan K. Amemiya, University of Tokyo, Japan Y. Takata, RIKEN, SPring-8 Center, Japan T. Ohta, University of Tokyo, Japan S. Shin, RIKEN, SPring-8 Center and University of Tokyo, Japan F. Komori, University of Tokyo, Japan |
| Correspondent: | Click to Email |
Recently, the atomic and electronic structures of magnetic nano-structure on surfaces have been intensively studied. We have investigated the initial growth of Co nano-islands on a nitrogen saturated Cu(001) c(2x2)-N surface by scanning tunneling microscopy (STM) and x-ray photoelectron spectroscopy and found that the nitrogen segregates on top of the Co islands and form Co-c(2x2)N structure.1 In the present study, we discuss the electronic structure of this system in terms of electron correlation effect investigated by x-ray absorption spectroscopy (XAS) at both Co 2p and N 1s absorption edges comparing with the growth process studied by STM. N 1s XAS spectrum shows gradual increase of the absorption intensity just above the Fermi level with the increase of Co coverage. This indicates that the bonding of N 2p with Cu 3d changed into that with Co 3d which has smaller number of d electrons than Cu. The result strongly supports the segregation of N atoms. In the Co 2p XAS spectrum, a shoulder-like structure was found at 3 eV higher energy side of the main peak both at L3 and L2 absorption edges. Its relative intensity of this "3 eV satellite" to the main peak gradually decreases with Co coverage below 2 ML on average. In the case of Ni thin film, the origin of 3 eV and 6 eV satellites in the Ni 2p XAS spectrum are attributed to the configuration interaction of correlated electrons (CI) and multiple scattering in absorption process (MS), respectively.2 We simulated XAS spectrum including the MS effect by FEFF code with the optimized atomic structure parameters obtained from first-principles calculation. However, the experimental results were not reproduced. Therefore, the origin of 3 eV satellites in our case is considered to be CI, indicating the presence of d7 configuration as well as d8. Comparing with the STM observation, the satellite is attributed to the mono-atomic height isolated Co-N islands. In such small islands, the charge transfer between Co and N would be different from that in the larger islands possibly by lattice compression.
1D. Sekiba et al., Surf. Sci. 590 (2005) 138.
2K. Amemiya et al., Phys. Rev. B72 (2005) 201404R.