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Impact of Stoichiometry on the Structure of van der Waals Layered GeTe/Sb 2 Te 3 Superlattices Used in Interfacial Phase‐Change Memory (iPCM) Devices
Author(s) -
Kowalczyk Philippe,
Hippert Françoise,
Bernier Nicolas,
Mocuta Cristian,
Sabbione Chiara,
BatistaPessoa Walter,
Noé Pierre
Publication year - 2018
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201704514
Subject(s) - materials science , superlattice , van der waals force , phase change memory , sputter deposition , stacking , epitaxy , stoichiometry , electron diffraction , molecular beam epitaxy , condensed matter physics , phase (matter) , optoelectronics , thin film , crystallography , sputtering , nanotechnology , diffraction , layer (electronics) , optics , chemistry , nuclear magnetic resonance , physics , organic chemistry , molecule
Van der Waals layered GeTe/Sb 2 Te 3 superlattices (SLs) have demonstrated outstanding performances for use in resistive memories in so‐called interfacial phase‐change memory (iPCM) devices. GeTe/Sb 2 Te 3 SLs are made by periodically stacking ultrathin GeTe and Sb 2 Te 3 crystalline layers. The mechanism of the resistance change in iPCM devices is still highly debated. Recent experimental studies on SLs grown by molecular beam epitaxy or pulsed laser deposition indicate that the local structure does not correspond to any of the previously proposed structural models. Here, a new insight is given into the complex structure of prototypical GeTe/Sb 2 Te 3 SLs deposited by magnetron sputtering, which is the used industrial technique for SL growth in iPCM devices. X‐ray diffraction analysis shows that the structural quality of the SL depends critically on its stoichiometry. Moreover, high‐angle annular dark‐field‐scanning transmission electron microscopy analysis of the local atomic order in a perfectly stoichiometric SL reveals the absence of GeTe layers, and that Ge atoms intermix with Sb atoms in, for instance, Ge 2 Sb 2 Te 5 blocks. This result shows that an alternative structural model is required to explain the origin of the electrical contrast and the nature of the resistive switching mechanism observed in iPCM devices.