Determination of the Anisotropic Elastic Properties of Rocksalt Ge₂Sb₂Te₅ by XRD, Residual Stress, and DFT

Abstract

The chalcogenide material Ge 2 Sb 2 Te 5 is the prototype phase-change material, with widespread applications for optical media and random access memory. However, the full set of its independent elastic properties has not yet been published. In this study, we determine the elastic constants of the rocksalt Ge 2 Sb 2 Te 5 , experimentally by X-ray diffraction (XRD) and residual stress and computationally by density functional theory (DFT). The stiffnesses (XRD-stress/DFT) in GPa are C 11 = 41/58, C 12 = 7/8, and C 44 = 8/12, and the Zener ratio is 0.46/0.48. These values are important to understand the effect of elastic distortions and nonmelting processes on the performances of increasingly small phase change data bits.

Multilayer Ge8Sb92/Ge2Sb2Te5 thin films: unveiling distinct resistance states and enhanced performance for phase change random access memory

“…Such robust stability positions GS/GST as highly valuable in the realm of PCRAM applications. 106) and ( 222) peaks signifies a transition of the GST layer to a HEX structure [20,21]. These changes align with the results from the R-T curve and microscopically explain the occurrence of two-phase transitions during the crystallization.…”

Crystallization behavior of N -doped Ge-rich GST thin films and nanostructures: An in-situ synchrotron X-ray diffraction study

“…A Williamson-Hall plot is not realistic (negative domain size) and the effective thermal expansion coefficient varies a lot. It is hypothesized that the elastic anisotropy of GST (Zener ratio of 0.5 [17]) may play an important role in these results. The measured values may be compared with the effective thermal expansion coefficients for: (i) a GST precipitate in a Ge matrix: 25.x10 -6 K -1 , where a spherical precipitate (thermal expansion coefficient ap) in an infinite matrix (thermal expansion coefficient am) is assumed, both media sharing the same isotropic elastic properties [18]:…”

Static and Dynamical Properties of heavy actinide Monopnictides of Lutetium

“…The Zener anisotropy factor A defined by Eqn. (2) measures the degree of anisotropy in a solid 34 . For an isotropic material, A = 1 whereas any value other than one indicates to anisotropy of a material.…”