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Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 47: Electronic Structure of Surfaces: Spectroscopy, Surface States

O 47.7: Poster

Tuesday, March 8, 2016, 18:15–20:30, Poster E

Low temperature scanning tunneling microscopy investigation of the phase change material Ge2Sb2Te5 — •Daniel Montag1, Jens Kellner1, Christian Pauly1, Marcus Liebmann1, Alessandro Giussani2, Volker Deringer3, Raffaella Calarco2, Richard Dronskowski3, and Markus Morgenstern11II. Physikalisches Institut B, RWTH Aachen University, Germany — 2Paul Drude Institut für Festkörperelektronik, Berlin, Germany — 3Institute of Inorganic Chemistry, RWTH Aachen University, Germany

We present a scanning tunneling microscopy (STM) study of the phase change material Ge2Sb2Te5 (GST), epitaxially grown on Si(111) in the metastable cubic phase and transferred in-situ in ultrahigh vacuum from the molecular beam epitaxy system to the STM. Despite the fact that GST is already commercially used, there is still no complete understanding of the ultra fast switching speed, the strong resistance change, and the high endurance of the Ge-Sb-Te alloys. One contribution to such a theory is an atomic scale understanding of the electronic properties of GST including the disorder caused by the relatively high vacancy content in the GeSb layers. We present dI/dV-field measurement on the atomic scale conducted at 8K. The analysis shows spatial fluctuations of the valence band onset and the gap width, wich is probably related to a random distribution of the Ge and Sb atoms. Moreover, particular structures within the STM images probing mainly the surface Te layer are compared with density functional theory calculations.

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