The atomic geometries of Cs and K adsorbed on Pd(111): the important role of the ionization potential of the substrate for the bonding

Abstract

Detailed LEED analyses provide structural data of the K and Cs overlayers on Pd(111) with (2×2) and (√3×√3)R30° periodicity. The alkali metal (AM)–Pd layer bond lengths and therefore the AM radii turned out to be 0.1 and 0.2 Å smaller on Pd(111) compared to related AM systems on Rh(111) and Ru(0001), respectively. This suggests a stronger AM–substrate bonding on Pd(111) than on Ru(0001) and Rh(111), which is also reflected by the thermal stability of the AM overlayers against desorption. The trend in the AM–substrate bond strengths follows the trend in the ionization potential of the substrates. This effect may support the AM–substrate bonding to be of charge transfer type.

References

1. (a) I. Langmuir and K. H. Kingdon, Phys. Rev., 1923, 21, 380; (b) I. Langmuir, J. Chem. Soc., 1932, 54, 2798; (c) J. B. Taylor and I. Langmuir, Phys. Rev., 1933, 44, 423.
2. R. W. Gurney, Phys. Rev., 1935, 47, 2798.
3. (a) N. D. Lang and A. R. Williams, Phys. Rev. B, 1978, 18, 616; (b) M. Scheffler, Ch. Droste, A. Fleszar, F. Maca, G. Wachutka and G. Barzel, Physica B, 1991, 172, 143; (c) G. Pacchioni and P. S. Bagus, Surf. Sci., 1993, 286, 317.
4. See, for example, D. M. Riffe, G. K. Wertheim and P. H. Citrin, Phys. Rev. Lett., 1990, 64, 571.
5. (a) E. Wimmer, A. J. Freeman, J. R. Hiskes and K. M. Karo, Phys. Rev. B, 1983, 28, 3074; (b) H. Ishida, Phys. Rev. B, 1990, 42, 10899.
6. R. D. Diehl and R. McGrath, J. Phys. C, 1997, 9, 951.
7. C. Kittel, Introduction to Solid State Physics, Wiley, New York, 5th edn., 1976.
8. R. D. Diehl and R. McGrath, Surf. Sci. Rep., 1996, 23, 43.
9. H. Over, H. Bludau, M. Skottke-Klein, G. Ertl, W. Moritz and C. T. Campbell, Phys. Rev. B, 1992, 45, 8638.
10. Handbook of Chemistry and Physics, CRC Press, Boca Raton, FL, 67th edn., 1986–1987, E-89.
11. H. Over, H. Bludau, M. Gierer and G. Ertl, Surf. Rev. Lett., 1995, 2, 409.
12. S. Schwegmann and H. Over, Surf. Sci., 1996, 360, 271.
13. W. Moritz, J. Phys. C, 1983, 17, 353.
14. (a) D. W. Marquardt, J. Soc. Ind. Appl. Math., 1963, 11, 431; (b) G. Kleinle, W. Moritz and G. Ertl, Surf. Sci., 1990, 238, 119; (c) H. Over, U. Ketterl, W. Moritz and G. Ertl, Phys. Rev. B, 1992, 46, 15438; (d) M. Gierer, H. Over and W. Moritz, unpublished work.
15. J. B. Pendry, J. Phys. C, 1980, 13, 937.
16. G. M. Lamble, R. S. Brooks, D. A. King and D. Norman, Phys. Rev. Lett., 1988, 61, 1112.
17. P. Kaukasoina, M. Lindroos, G. S. Leatherman and R. D. Diehl, Surf. Rev. Lett., 1997, 4, 1215.
18. S. V. Christensen, K. T. Nielsen, J. Nerlov, D. R. Batchelor and D. L. Adams, Surf. Sci., 1995, 339, L919.
19. C. Stampfl and M. Scheffler, Surf. Rev. Lett., 1995, 2, 317.
20. M. Gierer, H. Bludau, T. Hertel, H. Over, W. Moritz and G. Ertl, Surf. Sci., 1992, 279, L170.
21. S. Morè, W. Berndt, A. M. Bradshaw and R. Stumpf, Phys. Rev. B, 1998, 57, 9246.
22. J. Lahtinen, J. Vaari, T. Vaara, K. Kauraala, P. Kaukasoina and M. Lindroos, Surf. Sci., submitted.
23. C. Stampfl, M. Scheffler, H. Over, J. Burchhardt, M. M. Nielsen and D. L. Adams, Phys. Rev. Lett., 1992, 69, 1532.
24. D. Adler, I. R. Collins, K. Ding, S. Chandavarkar, X. Liang, S. Murray, G. S. Leatherman, P. D. Johnson, R. McGrath, R. D. Diehl and P. H. Citrin, Phys. Rev. B, 1993, 48, 17445.
25. D. Fisher, S. Chandavarkar, I. R. Collins, R. D. Diehl, P. Kaukasiona and M. Lindroos, Phys. Rev. Lett., 1992, 68, 2786.
26. P. J. Feibelman, Phys. Rev. B, 1997, 56, 10532.
27. R. A. dePaola, J. Hrbek and F. M. Hoffmann, J. Chem. Phys., 1985, 82, 2484.
28. H. Pirug and H. P. Bonzel, Surf. Sci., 1988, 194, 159.
29. P. Kaukasoina, M. Lindroos, R. D. Diehl, D. Fisher, S. Chandavarkar and I. R. Collins, J. Phys.: Condens. Matter, 1993, 5, 2875.
30. Y. D. Kim and H. Over, unpublished work.
31. G. S. Leatherman and R. D. Diehl, Phys. Rev. B, 1996, 53, 4939.
32. S. Chandavarkar, R. D. Diehl, A. Fakeé and J. Jupille, Surf. Sci., 1989, 211/212, 423.
33. W. C. Fan and A. Ignatiev, J. Vac. Sci. Technol. A, 1988, 6, 735.
34. R. D. Diehl and R. McGrath, Surf. Sci. Lett., 1995, 2, 409.