Regensburg 2010 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 9: Poster: Synthesis of Nanostructured Films by Self-organization, Thermoelectric Thin Films and Nanostructures, High-k and Low-k Dielectrics, Layer Deposition Processes, Layer Growth, Layer Properties, Application of Thin Films, Surface Modification, Hard and Superhard Coatings, Metal Layers

DS 9.27: Poster

Montag, 22. März 2010, 15:00–17:30, Poster D1

Optical analysis of ZnS:SiO₂ used as a Capping layer for phase change alloys — •Stephanie Grothe, Peter Jost, Michael Woda, Jenni Karvonen, and Matthias Wuttig — RWTH Aachen University, I. Physikalisches Institut (IA), 52056 Aachen, Germany

Phase change materials which can be switched rapidly between the amorphous and the crystalline phase are a promising candidate for new memory devices. These materials can be identified by a strong contrast in the optical dielectric constant between both phases which is due to resonant bonding [1]. As the optical dielectric constant can be evaluated from the dielectric function it is of great importance to measure the dielectric function with high accuracy.

However, an exact investigation of the dielectric constant is impeded by ageing effects which occur in the alloys after sputtering. First, we explored the dielectric function of Ge₁Sb₂Te₄ by infrared spectroscopy and spectroscopic ellipsometry and analysed the effect of ageing on the optical spectra.

Then, we investigate how these ageing effects can be prevented by the use of a suitable capping layer. We found out that a thin layer of ZnS:SiO₂ sputtered on top of the phase change material prevents ageing to a large extend. Additionally, after taking the ZnS:SiO₂ surface layer into account we can still investigate the optical properties of phase change materials which are capped by ZnS:SiO₂.

[1] Shportko, K. et al., Nature Mater. 7, 653-658 (2008).