The materials based on mixed GeTe/Sb2Te3 alloys show remarkable switchable opto-electronic properties between their amorphous and crystalline phases. They are therefore successfully implemented in rewritable optical DVD and Blu-Ray disks and are currently under intense investigation for future memory and photonic applications. Recently, it was shown that nanostructuring these alloys by growing GeTe and Sb2Te3 in the form of superlattices considerably improves the performance of the resulting phase-change memories. Despite this significant advance the origin of the improvement and the detailed switching mechanism were not clearly understood. Hence, the focus of this thesis is on the growth and characterization of such superlattices. Using particularly transmission electron microscopy the detailed crystal structure of such multilayers has been analyzed and explained in terms of the bonding nature of the alloys. Several switching mechanisms of superlattice phase-change memory in the literature were debated and shown that they were inconsistent with the actual structure of the films. In addition, it was shown that GeTe/Sb2Te3 superlattices can be an interesting platform to study mixed GeTe/Sb2Te3 alloys by illustrating in detail its thermal reconfiguration. In the final parts of the thesis the thin film growth is discussed with particular focus on engineering the substrate-film interface. In general, the results shed light on the structure and switching mechanism of GeTe/Sb2Te3 superlattice phase-change memories and pave way for growth of similar materials for ferroelectric, spintronic and thermoelectric applications.
|Translated title of the contribution||Structuur en reconfiguratie van epitaxiale GeTe/Sb2Te3 superroosters|
|Qualification||Doctor of Philosophy|
|Place of Publication||[Groningen]|
|Publication status||Published - 2017|