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 Morgenstern¹ — ¹II. 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.