Consequently, the knowledge of the proper local atomic arrangement in layered GST alloys is of paramount importance in order to understand the switching mechanism of iPCMs and their material properties. Investigations of atomic structure in such technologically relevant iPCM revealed that various layered GST crystal structures can be formed during iPCMs production 16, 17, 18. ![]() In particular, theoretical simulations showed that iPCMs can be a 3-D topological insulator 15 or a Dirac semimetal 11. Thus, the switching mechanism of iPCMs is determined by the local atomic arrangement in distinct layers 10, 11, 12, 13, which also defines the electronic properties of the materials 14. Interfacial PCMs (iPCMs) 9 or chalcogenide superlattices consisting of Sb 2Te 3 and GeTe multilayers are a promising candidate for data storage devices with reduced energy consumption since reversible transition between SET and RESET states is assumed to be constrained by motion of atoms in 1D instead of 3D as in the case of conventional PCM devices. The operating principle of conventional PCM devices is based on the reversible transformation between the amorphous and metastable crystalline phases triggered either by optical or electrical ultrafast pulses. Thin films of GST alloys are widely used as phase change materials (PCMs) in optical storage media 1, 2, 3, 4 and are also major contenders for the next generation non-volatile RAM 5, 6, 7, 8. Ge-Sb-Te (GST) compounds are of high interest due to their technologically outstanding optical and electronic properties. The comparison with image simulations based on various theoretical models reveals intermixed cation layers with pronounced local lattice distortions, exceeding those reported in literature. The results show that the thin films are prone to the formation of stacking disorder with individual building blocks of the Ge 2Sb 2Te 5, Ge 1Sb 2Te 4 and Ge 3Sb 2Te 6 crystal structures intercalated within randomly oriented grains. This work reveals the local atomic structure of trigonal Ge-Sb-Te thin films by using a combination of direct imaging of the atomic columns and theoretical image simulation approaches. However, due to the non-trivial influence of thermal diffuse scattering on the high-angle scattering signal, a detailed examination of the image contrast requires comparison with theoretical image simulations. Aberration-corrected scanning transmission electron microscopy allows direct imaging of local arrangement in the crystalline lattice with atomic resolution. ![]() In this view, a detailed knowledge of the atomic structure in such alloys is central to understanding the functional properties both in the more commonly utilized amorphous–crystalline transition and in recently proposed interfacial phase change memory based on the transition between two crystalline structures. Insights into the local atomic arrangements of layered Ge-Sb-Te compounds are of particular importance from a fundamental point of view and for data storage applications.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |