Atomic Manipulation on Metal Surfaces

Abstract

Half a century ago, Nobel Laureate Richard Feynman asked in a now-famous lecture what would happen if we could precisely position individual atoms at will [R.P. Feynman, Eng. Sci. 23, 22 (1960)]. This dream became a reality some 30 years later when Eigler and Schweizer were the first to position individual Xe atoms at will with the probe tip of a low-temperature scanning tunneling microscope (STM) on a Ni surface [D.M. Eigler, E.K. Schweizer, Nature 344, 524 (1990)].

Nowadays, such “atom manipulation” is used widely in research to build, probe, and manipulate objects at the scale of individual atoms. For example, two- and one-dimensional confined quantum structures were built atom-by-atom, and in those studies the STM was used to directly image the quantum nature of the electrons confined in those artificial structures [M.F. Crommie, C.P. Lutz, D.M. Eigler, Science 262, 218 (1993); H.C. Manoharan, C.P. Lutz, D.M. Eigler, Nature 403, 512 (2000); N. Nilius, T.M. Wallis, W. Ho, Science 297, 1853 (2002); C.R. Moon, L.S. Mattos, B.K. Foster, G. Zeltzer, W. Ko, H.C. Manoharan, Science 319, 782 (2008)]. Atom-manipulation has been used to build molecules from the constituting individual atoms or smaller molecules [S.-W. Hla, L. Bartels, G. Meyer, K.-H. Rieder, Phys. Rev. Lett. 85, 2777 (2000); J. Repp, G. Meyer, S. Paavilainen, F.E. Olsson, M. Persson, Science 312, 1196 (2006)]. And last, but not least, atom manipulation has been used to build devices on the atomic scale such as the molecules cascade [A.J. Heinrich, C.P. Lutz, J.A. Gupta, D.M. Eigler, Science 298, 1381 (2002)] and atomic switches [D.M. Eigler, C.P. Lutz, W.E. Rudge, Nature 352, 600 (1991); J.A. Stroscio, F. Tavazza, J.N. Crain, R.J. Celotta, A.M. Chaka, Science 313, 984 (2006)].

However, in all this body of work, the fundamental question – “how much force does it take to move an atom on a surface?” – had eluded experimental access until the advent of atomic-resolution noncontact AFM. Only in the last few years has it become possible to manipulate matter atom-by-atom with AFM [N. Oyabu, O. Custance, I. Yi, Y. Sugawara, S. Morita, Phys. Rev. Lett. 90, 176102 (2003); Y. Sugimoto, P. Jelinek, P. Pou, M. Abe, S. Morita, R. Pérez, O. Custance, Phys. Rev. Lett. 98, 106104 (2007)], most prominently in the controlled exchange of atoms within a surface layer of alloyed semiconductors [N. Oyabu, Y. Sugimoto, M. Abe, Ò. Custance, S. Morita, Nanotechnology 16, S112 (2005); Y. Sugimoto, M. Abe, S. Hirayama, N. Oyabu, Ò. Custance, S. Morita, Nat. Mater. 4, 156(2005)].

This chapter describes the use of a low-temperature scanning probe system that can be simultaneously operated as an STM and an AFM in the noncontact mode with sub-Angstrom oscillation amplitude. We will discuss how such a tool can be used to simultaneously measure the vertical and lateral forces exerted by the probe tip on the adsorbate before and during the controlled manipulation process.

Understanding the force necessary to move specific atoms on specific surfaces is one of the keys to further progress in nanoscience and will enable a deeper understanding of the atomic-scale processes at the heart of future nanotechnology endeavors, furthering progress toward nanoscale devices.