TY - JOUR
T1 - Crystallization of Ge2Sb2Te5 under high hydrostatic pressures
T2 - Differences in nanoscale atomic ordering in as-deposited and pressure-induced amorphous phases
AU - Krbal, M.
AU - Kolobov, A. V.
AU - Hanfland, M.
AU - Fons, P.
N1 - Funding Information:
This work was supported by the Czech Science Foundation (project no. 19-17997S ) and Ministry of Youth, Education and Sports of the Czech Republic (project no. LM2018103 ). The research was also partially (AVK) supported by the Ministry of Education of the Russian Federation (project No. FSZN-2020-0026 ). Measurements were performed at ESRF using beamline ID09A within the CH3988 and HS3510 proposals.
Publisher Copyright:
© 2021 The Author(s)
PY - 2021/9/5
Y1 - 2021/9/5
N2 - The crystallization process acts as a bottleneck to the development of phase-change memory devices. Here, we compare the crystallization of as-deposited and pressure-induced amorphous phases of Ge2Sb2Te5 under hydrostatic pressures up to 8.5 GPa. The as-deposited phase fully converts to a stressed metastable cubic phase (at ca. 135 °C) at pressures below 3 GPa and remains cubic up to the maximum temperature used (240 °C). At higher pressures, the as-deposited phase partially crystallizes directly into the stable hexagonal phase at a significantly lower temperature (110 °C), however a significant volume fraction of the amorphous phase remains even for temperatures as high as 240 °C. The intensities of the Bragg diffraction peaks dramatically decrease with increasing pressure, further underscoring the suppression of crystal growth. In stark contrast, the pressure-induced amorphous phase- due to memory effects originating from the crystalline phase - crystallizes at ambient conditions at a lower temperature than its as-deposited counterpart. Furthermore, the pressure-induced amorphous phase also fully transforms directly into the hexagonal modification at pressures up to ca. 5 GPa. At higher pressure (8.5 GPa), an orthorhombic phase is formed. Different from the as-deposited phase, the crystallization temperature of pressure-induced amorphous Ge2Sb2Te5 increases with pressure. The results reported here demonstrate that differences in nanoscale ordering in as-deposited (statistically ordered) and pressure-induced (chemically ordered) amorphous phases dramatically influence crystallization and will serve as a guideline for insightful development of phase-change devices.
AB - The crystallization process acts as a bottleneck to the development of phase-change memory devices. Here, we compare the crystallization of as-deposited and pressure-induced amorphous phases of Ge2Sb2Te5 under hydrostatic pressures up to 8.5 GPa. The as-deposited phase fully converts to a stressed metastable cubic phase (at ca. 135 °C) at pressures below 3 GPa and remains cubic up to the maximum temperature used (240 °C). At higher pressures, the as-deposited phase partially crystallizes directly into the stable hexagonal phase at a significantly lower temperature (110 °C), however a significant volume fraction of the amorphous phase remains even for temperatures as high as 240 °C. The intensities of the Bragg diffraction peaks dramatically decrease with increasing pressure, further underscoring the suppression of crystal growth. In stark contrast, the pressure-induced amorphous phase- due to memory effects originating from the crystalline phase - crystallizes at ambient conditions at a lower temperature than its as-deposited counterpart. Furthermore, the pressure-induced amorphous phase also fully transforms directly into the hexagonal modification at pressures up to ca. 5 GPa. At higher pressure (8.5 GPa), an orthorhombic phase is formed. Different from the as-deposited phase, the crystallization temperature of pressure-induced amorphous Ge2Sb2Te5 increases with pressure. The results reported here demonstrate that differences in nanoscale ordering in as-deposited (statistically ordered) and pressure-induced (chemically ordered) amorphous phases dramatically influence crystallization and will serve as a guideline for insightful development of phase-change devices.
KW - Crystallization
KW - High pressure study
KW - Phase-change material
KW - X-ray diffraction
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U2 - 10.1016/j.jallcom.2021.159980
DO - 10.1016/j.jallcom.2021.159980
M3 - Article
AN - SCOPUS:85104631304
SN - 0925-8388
VL - 874
JO - Journal of Alloys and Compounds
JF - Journal of Alloys and Compounds
M1 - 159980
ER -