Dresden 2009 – wissenschaftliches Programm

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SYSO: Symposium Self-organizing Surfaces and Interfaces

SYSO 6: Self-Organizing Surfaces and Interfaces V

SYSO 6.5: Vortrag

Donnerstag, 26. März 2009, 15:00–15:15, GÖR 226

DFT-study of Pt induced Nanowires on Ge(001) — •Danny Vanpoucke and Geert Brocks — University of Twente, Enschede, The Netherlands

The deposition of Pt on a Ge(001) surface gives rise to the spontaneous formation of nanowire (NW) arrays. These one atom thick NWs are defect and kink free with a length only limited by the underlying β-terrace. We present an ab-initio density functional theory (DFT) study of the underlying β-terrace and the NWs. For over 100 geometries the total energies were calculated and a comparison was made between their simulated scanning tunneling microscope (STM) images and the experimental STM images of this system. From this we identified the geometry of the β-terrace and present a formation path for the NWs as function of increasing local Pt density. Our results show the β-terrace has a structure similar to the clean Ge(001) surface, but with one in four Ge surface atoms replaced by a Pt atom giving rise to a checkerboard pattern of Pt-Ge and Ge-Ge surface dimers. Furthermore we show that solitary NWs have a slightly different structure than NWs in NW arrays, and connect the difference in geometry to the difference in observed experimental STM images. Most remarkably, we show by direct comparison to experimental STM images that the experimentally observed "platinum" NWs[1], in fact, consist of germanium atoms located in Pt lined troughs[2].
O. Gurlu et al., Appl. Phys. Lett. 83, 4610 (2003)
D. E. P. Vanpoucke and G. Brocks, Phys. Rev. B 77, 241308(R) (2008)