Dresden 2014 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 40: Focus Session: Resistive Switching by Redox and Phase Change Phenomena VII (Optical properties and theory of PC materials)
DS 40.3: Vortrag
Donnerstag, 3. April 2014, 12:00–12:15, CHE 89
Understanding Stability Trends at Clean and Oxidized GeTe Surfaces — •Volker Deringer1 and Richard Dronskowski1,2 — 1Institute of Inorganic Chemistry, RWTH Aachen University, 52056 Aachen, Germany — 2Jülich–Aachen Research Alliance (JARA)
Phase-change memory devices are becoming smaller and smaller, necessarily so. In turn, the surfaces of phase-change materials surely deserve increased attention: the surface–volume ratio rises dramatically on the nanoscale, and surface oxidation (detrimental to long-term switching capability) becomes important. Here, we present comprehensive DFT computations for the prototypical germanium telluride (GeTe) surfaces. We have simulated freshly cleaved and reconstructed surfaces, as well as molecular O2 adsorption and higher oxygen coverage.
The predicted stability trends are then investigated and rationalized at the hand of chemical-bonding analysis: by partitioning the electronic structure into bonding (stabilizing) and antibonding contributions, we offer a straightforward explanation for why one type of surface termination is favorable while the other is not. This model can be directly extended to surface oxidation: more stable surfaces are rather inert whereas others readily react with oxygen, thereby reducing unfavorable antibonding interactions at the surface. Our simulations of oxidized GeTe surfaces agree well with previous XPS measurements, and the atom-resolved and chemical-bonding techniques provide a worthwhile additional viewpoint.