Low Temperature Surface Diffusion on Metallic Surfaces

Hervé Bulou (1) , Fabrice Scheurer (1) , Christine Boeglin (1) , Philippe Ohresser (2) , Stefan Stanescu (2) , Emilie Gaudry (3)

1 IPCMS - Institut de Physique et Chimie des Matériaux de Strasbourg
2 SSOLEIL - Synchrotron SOLEIL
3 LSG2M - Laboratoire de Science et Génie des Matériaux et de Métallurgie

We present a study of the atomic surface diffusion at low temperature of Cr adatoms deposited on Cu(100), Cu(111), and Au(111) surfaces. Time-dependent X-ray magnetic circular dichroism (XMCD), Monte Carlo simulations, and the Kimball−Shortley iterative method are used to evidence a mechanism of quantum tunneling involved in the Cr adatom surface diffusion at temperatures below 40 K. We show that the XMCD line shape is correlated to the atomic configuration of Cr deposited on a metallic surface. A diffusion rate ranging from 0.03 Hz for Cu(100) to 30 Hz for Au(111) at 10 K is reported from the time evolution of the XMCD line shape. A quantum equation of motion for the Cr adatom is derived and solved by using a Kimball−Shortley iterative method. Good agreement between the calculated Bohr periods and the experimental diffusion rates is reported.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Hervé Bulou, Fabrice Scheurer, Christine Boeglin, Philippe Ohresser, Stefan Stanescu, et al.. Low Temperature Surface Diffusion on Metallic Surfaces. Journal of Physical Chemistry C, 2009, 123 (11), pp.4461-4467. ⟨10.1021/jp805674n⟩. ⟨hal-00978018⟩