Characterization of GeSbTe Films by Spectroscopic Ellipsometry for Rewritable Optical Discs

The NIR range contains the most important information to analyze the different GeSbTe structures.

Experimental data of the 5 GeSbTe samples.

Phase change optical recording is a challenging technology for data storage that is used for CD and DVD rewritable discs. It is based on localized laser induced heating of a thin layer to cause a phase transition from the crystalline to amorphous state. This transformation results in optical reflectance differences.

Currently phase change rewritable optical discs are mainly based on two families of phase change materials. Pseudo-binary alloys based on GeTe-Sb2Te3 (here referred to as GeSbTe) or quaternary AgInSbTe alloys. The choice of material is governed by the specific requirements of the application.

An accurate measurement of the thickness and optical constants of the multilayer system is important because mechanical, optical and thermal characteristics are influenced by the entire layer structure. Spectroscopic ellipsometry allows the simultaneous determination of these properties quickly and with high accuracy.

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Characterization of GeSbTe films by Spectroscopic Ellipsometry for Rewritable Optical Discs
DescriptionSpectroscopic ellipsometry is a powerful technique for high accuracy characterization of the thickness and optical constants of GeSbTe multilayer system for rewritable optical disc applications. It was shown that measurement in the NIR range gives better accuracy for the analysis of these types of material. The use of the multiple sample analysis reduces parameter correlations and errors for the thinnest layers. Owing to the advanced modeling features included in the DeltaPsi2 software, it is a straightforward procedure to analyze such structures even with layers deposited on both sides of the substrate.
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