Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 4: Elektronische Struktur I

O 4.2: Vortrag

Montag, 24. März 2003, 11:30–11:45, FOE/ANOR

Theoretical analysis of STM/STS experiment for NiFe alloy surface: electronic and topographic features — •František Máca^1,2, Josef Redinger², and Raimund Podloucky² — ¹Institute of Physics AS CR, Na Slovance 2, CZ-182 21 Praha 8, Czech Republic — ²CMS TU Wien, Getreidemarkt 9, A-1060 Wien, Austria

Scanning tunneling microscopy and spectroscopy (STM and STS)provides a possibility to study directly the electronic structure of disordered alloy surfaces. The combination with first principles calculations permits a detailed analysis of observed data. We compare results obtained by ab initio density functional calculations with STM scans for NiFe invar surface.

Different ordered surface fcc-like structures are used to simulate the alloy surface. The ab initio atomic force minimizations shows a clear tendency to surface rumpling such that Fe atoms move outwards and Ni atoms inwards. Buckling of the top surface NiFe monolayer depends on the subsurface local chemical composition. We calculate also the electronic structure and charge redistribution in the surface region and discuss spectral features observed in the STS experiment.