The rapidly increasing net amount of digital information requires higher data- storage capacities and transfer rates. Consequently, there is a need for a continuous improvement of the media concept and design. Phase change recording technology offers attractive features for erasable data storage with high density. Digital information can be written, erased and re- written repetitively using optical techniques. They can be characterized by two stable physical structures that exhibit significantly different optical properties. Further optimisation of this technology requires the determination of crystallisation kinetics and comprehensive understanding of the underlying mechanisms. To speed up the search for faster materials we employ concepts of combinatorial material synthesis by producing films with a stoichiometry gradient by thermal evaporation. Then laterally resolved secondary neutral mass spectroscopy (SNMS) combined with the static tester is used to identify the composition with superior properties for phase change applications. In this work, we have prepared and investigated the crystallisation kinetics of GeSbTe stoichiometry libraries. Therefore, germanium, antimony, tellurium, and GeTe have been used as evaporant materials. By superposing the vapours of the single elements, stoichiometry libraries can be prepared. The resulting compounds have then been compared to the results of well-known sputter prepared GeSbTe compounds in order to perform the proof of concept. The properties of these materials are compared in regard to data storage applications. The preparation technique presented in this work, allows two approaches to prepare the materials: the static and the dynamic mode. First, samples prepared in static mode have lateral stoichiometry gradients. Hence, they can be screened for properties like the minimum time for crystallisation or optical contrast with the static tester. For a GeSb2Te4 library, we have seen that compounds close to GeSb2Te4 have the shortest crystallisation times. We observe that the minimal times for crystal- lisation increases with the distance from the pseudo-binary line, whereas the maximum change in reflection decreases, respectively. This result corroborates the believe that especially the materials along the pseudo-binary line are the most suitable candidates for re-writable optical data storage applications. Statically prepared samples have furthermore been studied with lateral resolved spectral ellipsometry to determine dependence of stoichiometry on the optical properties. The simulated optical contrast between the amorphous and crystalline structure corroborates the contrast observed by crystallisation experiments. Furthermore, by preparing samples in dynamic mode, single stoichiometry films are obtained. These samples can then be studied with macroscopic techniques such as temperature dependent electrical measurements, which has been employed to study the kinetics of the structural changes. Corroborative x-ray diffraction measurements reveal that upon annealing the amorphous GeTe, Ge2Sb2Te5 and GeSb2Te4 films crystallise to a cubic structure, followed by a hexagonal structure upon further annealing. Ge4SbTe5, Sb2Te, and Sb2Te3 films crystallize in only one phase namely cubic and hexagonal structures, respectively. The cubic structures for GeTe, Ge2Sb2Te5, Ge4SbTe5, and GeSb2Te4 alloys are identified with NaCl-type. X-ray reflectometry measurements show that these transformations are charac- terized by a density increase resulting in a thickness decrease.
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