Dresden 2009 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 48: Poster 2
HL 48.1: Poster
Thursday, March 26, 2009, 15:00–17:30, P2
Scanning tunneling microscopy and spectroscopy of phase change alloys — •Dinesh Subramaniam1, Christian Pauly1, Marco Pratzer1, Marcus Liebmann1, Pascal Rausch2, Michael Woda2, Matthias Wuttig2, and Markus Morgenstern1 — 1II. Physikalisches Institut B, RWTH Aachen, Otto-Blumenthal-Straße, 52074 Aachen — 2I. Physikalisches Institut A, RWTH Aachen, Otto-Blumenthal-Straße, 52074 Aachen
Phase change random access memory (PCRAM) is a very promising candidate for the next generation of memories. In contrast to the standard Si-based RAM, PCRAM is a non-volatile storage system which exploits the high electrical contrast between the amorphous and the crystalline phase. However, the origin of this contrast is not well understood. Scanning tunneling microscopy gives insight into the local atomic structure and the electronic properties of phase change materials. Using the topography mode of STM, we realized images of Ge1Sb2Te4 on the nanometer down to the atomic scale, revealing the morphology as well as the complex atomic arrangement of the sputter-deposited material. The spectroscopy mode enabled us to analyse the local density of states in the amorphous and crystalline phase. The band gap varied continuously from 0.5 eV in the amorphous phase to 0.2 eV in the crystalline phase. The Fermi level moved from the center of the gap in the amorphous phase into the valence band within the crystalline phase.