| AVS 64th International Symposium & Exhibition | |
| Surface Science Division | Wednesday Sessions |
| Session SS-WeM |
| Session: | Deposition and Growth at Surfaces |
| Presenter: | Enrique G. Michel, Universidad Autonoma de Madrid |
| Authors: | M. Valbuena, Universidad Autonoma de Madrid C. Quiros, Universidad de Oviedo E. Salagre, Universidad Autónoma de Madrid A. Oliva, Universidad Autonoma de Madrid M. Plaza, Universidad Autonoma de Madrid J. Martinez-Blanco, Universidad Autonoma de Madrid P. Segovia, Universidad Autonoma de Madrid E.G. Michel, Universidad Autonoma de Madrid |
| Correspondent: | Click to Email |
The formation of a surface generates in general a spontaneous contraction of the surface plane to re-establish the equilibrium (surface relaxation) [1]. There are many surfaces where the spontaneous contraction is very small or even it is an expansion instead of a contraction [2]. Interestingly, there are several prominent cases of surfaces exhibiting an anomalous expansion that also present a surface electronic state with a significant density of states [2,3,4,5]. Theoretical calculations have found [3] that the sign and magnitude of the relaxation of the topmost atomic layers of Al(100) is mainly determined by the rearrangements of the surface state charge. In short, the presence of a surface state increases the surface charge density, and this affects the surface relaxation. Analogous calculations show that Au(110) and Au(100) (without a high density of surface states) present a conventional surface relaxation (contraction), while Au(111) (with a prominent Shockley surface state) is characterized by an anomalous expansion [6]. These findings point towards a strong involvement of the density of surface states in the relaxation finally observed.
We report experimental results monitoring directly the change in surface relaxation when the surface charge in the surface state is modified. To this end, we tune the Au(111) surface state filling in a controlled way, by depositing suitable acceptor or donor molecular species. Then, we measure the surface relaxation as a function of the surface state charge, using surface x-ray diffraction (SXRD). The SXRD analysis includes the measurement of several Crystal Truncation Rods as a function of coverage of the donor or acceptor species. The results are fitted using standard procedures and provide the surface relaxation. The charge contents in the surface state is also experimentally determined from ARPES measurements of the Fermi contour for different coverages. Our results establish a direct relationship between surface relaxation and charge contents in the Au(111) surface state and shed light on the nature and deep origin of the surface relaxation process.
[1] S.Y. Tong “Surface Crystallography by LEED: Theory, Computation, and Structural Results”, Springer.
[2] H.L. Davis et al , Phys. Rev. Lett. 68, 2632 (1992).
[3] V. Chis and B. Hellsing, Phys. Rev. Lett. 93, 226103 (2004).
[4] F. Reinert et al, Phys. Rev. B 63, 115415 (2001).
[5] J. Sun et al, New Journal of Phys. 12, 063016 (2010).
[6] Li Guan et al, Solid. State. Commun. 149, 1561 (2009).