Scanning tunneling microscopy of binary-alloy surfaces: Is chemical contrast a consequence of alloying?

W. A. Hofer, G. Ritz, W. Hebenstreit, M. Schmid, P. Varga, J. Redinger1, and R. Podloucky2

Institut für Allgemeine Physik, Technische Universität Wien, A-1040 Wien, Austria
1Institut für Technische Elektrochemie, Technische Universität Wien, A-1060 Wien, Austria
2Institut für Physikalische Chemie, Universität Wien, A-1090 Wien, Austria

Surf. Sci. Lett. 405 (1998) L514-L519

Recent STM studies achieved chemical resolution on PtRh and PtNi alloy surfaces. By a first-principles method employing the Tersoff-Hamann model, we have simulated STM scans on PtRh and PtNi (100) surfaces by calculating the apparent heights of individual surface atoms. The difference in apparent heights between Pt and Rh atoms is caused by changes in the density of states due to alloying. The simulations for the PtNi(100) surface, however, yield apparent heights of Pt and Ni atoms below atomic resolution, indicating that in the experiment tip-sample interactions are responsible for chemical and atomic resolution.

Corresponding author: P. Varga (varga< encoded email address >).

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