Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 66: Electronic Structure of Surfaces

O 66.4: Poster

Wednesday, March 18, 2015, 18:15–21:00, Poster A

Three-dimensional band mapping and spin-polarized states in the phase change material Ge₂Sb₂Te₅ — •Marcus Liebmann¹, Christian Pauly¹, Jens Kellner¹, Jos Boschker², Rui Ning Wang², Evangelos Golias³, Jaime Sanchez-Barriga³, Oliver Rader³, Raffaella Calarco², and Markus Morgenstern¹ — ¹II. Inst. Phys. B, RWTH Aachen University — ²Paul-Drude-Institut für Festkörperelektronik, Berlin — ³Helmholtz-Zentrum für Materialien und Energie, BESSY, Berlin

We present an angle-resolved photoemission (ARPES) study of the ternary phase change material Ge₂Sb₂Te₅, epitaxially grown on Si(111) in the metastable cubic phase, transferred in-situ in ultrahigh vacuum from the molecular beam epitaxy system to the analysis chamber. This material serves, e.g., in DVDs as a fast switchable material (1 ns) between the metallic cubic and an insulating amorphous phase. Recently, the observation of an inverted valence band provided evidence of non-tivial Z₂ topology [1], opening up the perspective of ns-switching between a topological crystalline and an insulating amorphous phase. We performed a three-dimensional mapping of the band structure by variation of the photon energy (15-31 eV) and found the center of the bulk valence band about 130 meV below the Fermi energy and away from the center of the Brillouin zone. A spin polarization of nearly 100% close to the Fermi energy has been observed by spin-polarized ARPES. We show a detailed analysis of the involved states near the Fermi energy contributing to the transport.

[1] C. Pauly et al., Appl. Phys. Lett. 103, 243109 (2013).