Nanostructure research and electron microscopy
Local structure of phase change materials and van der Waals-bonded chalcogenide-based heterostructures for memory application
In recent years, chalcogenide-based phase change materials attract much attention due to their important optical and electronic properties. The alloys exhibit unique materials properties and are used as active layer for data storage in phase change memory (PCM) technology (e.g. Intel Optane Memroy). Currently, the Phase Change Random Access Memory (PCRAM) relies on the reversible transition between amorphous and crystalline states. However, power consumption is a critical issue. Nanoscale engineering of phase change materials has been shown to be a promising approach for further development of the materials with lower power consumption. The approach is based on the synthesis of chalcogenide-based superlattices (SLs), also known as interfacial PCM (iPCM). These improved performances have been ascribed to the fact that the switching in iPCM cells is a melting-free mechanism. Moreover, storage devices based on solely crystalline structures will benefit of much stable resistance in addition. Theoretical models of the reversible switching and resistance contrast in SLs focus on the stacking sequence of particular layers. Consequently, the knowledge of the proper local atomic arrangement in chalcogenide-based materials is of paramount importance for understanding the switching mechanisms and their material properties as well as for designing of new materials with advance properties.
The research activity of the group aims at understanding the interplay between the growth, local structure and properties of chalcogenide-based phase change alloys. The materials under investigation are epitaxial chalcogenide-based thin films and SLs grown by pulsed laser deposition (in cooperation with the R&D Focus Non-thermal Thin Film Deposition and Nanostructures). The local structure is revealed by combination of state-of-the art transmission electron microscopy and theoretical image simulation.
Selected publications
- A. Lotnyk, I. Hilmi, U. Roß, B. Rauschenbach
Van der Waals interfacial bonding and intermixing in GeTe-Sb2Te3-based superlattices
Nano Res. 11 (2018) 1676-1686
doi.org/10.1007/s12274-017-1785-y - M. Behrens, A. Lotnyk, U. Roß, J. Griebel, P. Schumacher, J. W. Gerlach, B. Rauschenbach
Impact of disorder on optical reflectivity contrast of epitaxial Ge2Sb2Te5 thin films
CrystEngComm 20 (2018) 3688 – 3695
10.1039/C8CE00534F - I. Hilmi, A. Lotnyk, J. W. Gerlach, P. Schumacher, B. Rauschenbach
Epitaxial formation of cubic and trigonal Ge-Sb-Te thin films with heterogeneous vacancy structures
Mater. Design 115 (2017) 138-146
doi.org/10.1016/j.matdes.2016.11.003 - N.S. Gunning, T. Dankwort, M. Falmbigl, U. Roß, G. Mitchson, D.M. Hamann, A. Lotnyk, L. Kienle, D.C. Johnson
Expanding the concept of van der Waals heterostructures to interwoven 3D Structures
Chem. Mater. 29 (2017) 8292-8298
https://pubs.acs.org/doi/10.1021/acs.chemmater.7b02605 - A. Lotnyk, U. Roß, S. Bernütz, E. Thelander, B. Rauschenbach
Evaluation of local atomic arrangements and lattice distortions in layered Ge-Sb-Te crystal structures
Sci. Rep. 6 (2016) 26724
https://doi.org/10.1002/9783527808465.EMC2016.6108 - U. Roß, A. Lotnyk, E. Thelander, B. Rauschenbach
Microstructure evolution in pulsed laser deposited epitaxial Ge-Sb-Te chalcogenide thin films
Journal of Alloys and Compounds 676 (2016) 582-590
doi.org/10.1016/j.jallcom.2016.03.159 - U. Roß, A. Lotnyk, E. Thelander, B. Rauschenbach
Direct imaging of crystal structure and defects in metastable Ge2Sb2Te5 by quantitative aberration-corrected scanning transmission electron microscopy
Appl. Phys. Lett. 104 (2014) 121904
https://doi.org/10.1063/1.4869471