New insights on the metastable cubic GexSbyTez phase
Abstract
A C TGe-rich Ge-Sb-Te (GGST) alloys are of high interest for industrial production of complementary metal-oxidesemiconductor integrated phase change random access memories (PCRAM) of high performance. BEOLintegrated GGST-based PCRAM constitute a relevant solution for low-power on-chip non-volatile memory production and in-memory computing, addressing new challenges of automotive and artificial intelligence applications for example. During cycling, in the low-resistive SET state, the crystallized GGST alloy is mainly made of nano-grains of two phases: diamond Ge and a ternary rock-salt (RS) Ge-Sb-Te (GST) phase. The RS-GST phase is metastable and generally assumed to exhibit the stoichiometry Ge 2 Sb 2 Te 5 corresponding to the stable hexagonal Ge 2 Sb 2 Te 5 compound. However, recent works suggest that this metastable RS-GST phase is not stoichiometric and can accept higher Ge contents, meaning that the Ge content of RS-GST could vary depending on the Ge excess level in the GGST alloy compared to the Ge 2 Sb 2 Te 5 reference stoichiometry. Consequently, the performance of GGST-based PCRAMs could vary with Ge composition of GGST alloy, suggesting the existence of an ideal GGST alloy composition showing a good compromise between crystallization temperature, programming current density, resistance, threshold voltage drift… In the present work, the structure and composition of crystallized GGST films elaborated through Ge, Sb, and Te co-sputtering were studied by X-ray diffraction, high resolution transmission electron microscopy, and atom probe tomography. The metastable RS-GST phase crystallized in GGST films exhibiting a Ge excess between 23% and 42% is found to be able to incorporate a large amount of Ge, of about 50 at% and sometimes beyond.
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BibTeX
@article{perrintoinin2026insights,
title = {{New insights on the metastable cubic GexSbyTez phase}},
author = {Jacques Perrin-Toinin and Alain Portavoce and Jacopo Remondina and Hamza Khelidj and Martiane Cabie and Thomas Neisius and Guillaume Roland and Yuan Yu and Maxime Bertoglio and Marion Descoins and Matthias Wuttig and Frédéric Lorut and Elisa Petroni},
journal = {Materialia},
year = {2026},
month = oct,
doi = {10.1016/j.mtla.2026.102836},
url = {https://hal.science/hal-05786422v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - New insights on the metastable cubic GexSbyTez phase
AU - Jacques Perrin-Toinin
AU - Alain Portavoce
AU - Jacopo Remondina
AU - Hamza Khelidj
AU - Martiane Cabie
AU - Thomas Neisius
AU - Guillaume Roland
AU - Yuan Yu
AU - Maxime Bertoglio
AU - Marion Descoins
AU - Matthias Wuttig
AU - Frédéric Lorut
AU - Elisa Petroni
PY - 2026
DA - 2026/10/08
JO - Materialia
DO - 10.1016/j.mtla.2026.102836
UR - https://hal.science/hal-05786422v1
AB - A C TGe-rich Ge-Sb-Te (GGST) alloys are of high interest for industrial production of complementary metal-oxidesemiconductor integrated phase change random access memories (PCRAM) of high performance. BEOLintegrated GGST-based PCRAM constitute a relevant solution for low-power on-chip non-volatile memory production and in-memory computing, addressing new challenges of automotive and artificial intelligence applications for example. During cycling, in the low-resistive SET state, the crystallized GGST alloy is mainly made of nano-grains of two phases: diamond Ge and a ternary rock-salt (RS) Ge-Sb-Te (GST) phase. The RS-GST phase is metastable and generally assumed to exhibit the stoichiometry Ge 2 Sb 2 Te 5 corresponding to the stable hexagonal Ge 2 Sb 2 Te 5 compound. However, recent works suggest that this metastable RS-GST phase is not stoichiometric and can accept higher Ge contents, meaning that the Ge content of RS-GST could vary depending on the Ge excess level in the GGST alloy compared to the Ge 2 Sb 2 Te 5 reference stoichiometry. Consequently, the performance of GGST-based PCRAMs could vary with Ge composition of GGST alloy, suggesting the existence of an ideal GGST alloy composition showing a good compromise between crystallization temperature, programming current density, resistance, threshold voltage drift… In the present work, the structure and composition of crystallized GGST films elaborated through Ge, Sb, and Te co-sputtering were studied by X-ray diffraction, high resolution transmission electron microscopy, and atom probe tomography. The metastable RS-GST phase crystallized in GGST films exhibiting a Ge excess between 23% and 42% is found to be able to incorporate a large amount of Ge, of about 50 at% and sometimes beyond.
SN - 2589-1529
ER -