Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 49: Poster: Nanostructures on Surfaces I

O 49.20: Poster

Dienstag, 13. März 2018, 18:15–20:30, Poster A

Low-temperature STM measurements on the stable phase of Ge₁Sb₂Te₄ grown by MOVPE — •Philipp Küppers¹, Christian Holl¹, Marcus Liebmann¹, Albert Ratajczak², Detlev Grützmacher², Hilde Hardtdegen^2,3, and Markus Morgenstern¹ — ¹II. Physikalisches Institut B, RWTH Aachen — ²Peter-Grünberg-Institut 9, Forschungszentrum Jülich — ³Ernst Ruska-Centrum für Mikroskopie und Spektroskopie mit Elektronen 2, Forschungszentrum Jülich

Ge₁Sb₂Te₄ is a phase change material, similarly used in DVDs and random access memory. It exhibits a metastable and a stable crystalline phase which differ only by their stacking sequence. Here, we study the stable phase of Ge₁Sb₂Te₄, grown by metalorganic vapor phase epitaxy (MOVPE) using scanning tunneling microscopy (STM) and spectroscopy at 6 K. We present atomically resolved flat and defect-free terraces as large as 30 × 30 nm² revealing a Te termination. Local density of states (LDOS) measurements show subsurface defects as triangular features in LDOS maps. While contacting the sample with a Cr (W) tip such that the resistivity decreases to ≈ 10⁴ Ω, we observe an additional sharp drop in resistivity by an order of magnitude after ramping the voltage to 0.8 V (1.1 V). The process is reversible by removing and recontacting the tip at the same position. Possible explanations of the switching process are discussed.