https://doi.org/10.1140/epjb/e2008-00168-y
Reduction of surface coverage of finite systems due to geometrical steps
1
Forschungszentrum Dresden-Rossendorf, PF 51 01 19, 01314 Dresden, Germany
2
Max-Planck-Institute for the Physics of Complex Systems, Noethnitzer Str. 38, 01187 Dresden, Germany
3
Institute of Physics, Chemnitz University of Technology, 09107 Chemnitz, Germany
4
Jacobs University Bremen gGmbH, 28759 Bremen, Germany
Corresponding author: a morawetz@physik.tu-chemnitz.de
Received:
8
December
2007
Revised:
19
March
2008
Published online:
19
April
2008
The coverage of vicinal, stepped surfaces with molecules is simulated with the help of a two-dimensional Ising model including local distortions and an Ehrlich-Schwoebel barrier term at the steps. An effective two-spin model is capable to describe the main properties of this distorted Ising model. It is employed to analyze the behavior of the system close to the critical points. Within a well-defined regime of bonding strengths and Ehrlich-Schwoebel barriers we find a reduction of coverage (magnetization) at low temperatures due to the presence of the surface step. This results in a second, low-temperature transition besides the standard Ising order-disorder transition. The additional transition is characterized by a divergence of the susceptibility as a finite-size effect. Due to the surface step the mean-field specific heat diverges with a power law.
PACS: 64.60.Fr – Equilibrium properties near critical points, critical exponents / 64.70.Nd – Structural transitions in nanoscale materials / 75.70.Ak – Magnetic properties of monolayers and thin films / 68.35.Rh – Phase transitions and critical phenomena
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2008