Applications

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.

Five different samples with increasing thickness of GeSbTe were characterized. The samples are composed of the phase-change layer containing s GeSbTe alloy deposited onto a dielectric layer of SiO2, the substrate of c-Si. Sample 1 exhibits interference fringes in the visible; samples 2 to 5 exhibit the same experimental data in the visible and FUV range.

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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Spectroscopic Ellipsometer from FUV to NIR: 190 to 2100 nm

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