Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 49: Poster: Nanostructures on Surfaces I
O 49.20: Poster
Tuesday, March 13, 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 Hardtdegen2,3, 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.