Density changes upon crystallization of Ge2Sb2.04Te4.74 films

Abstract

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Atomistic origins of the phase transition mechanism in Ge2Sb2Te5

“…Using this procedure, we will be able to take the volume changes in amorphization as a fingerprint in which to compare our multiple configurations and potential pathways against experimental results. 10,36,62 First, we compared the a-GST structures generated using cubic and hexagonal unit cells from high temperature MD simulations. The pair correlation functions for all pairs of atoms ͑Ge-Te, Ge-Sb, Sb-Te, Ge-Ge, Sb-Sb, and Te-Te͒ were obtained by averaging the pair correlation functions over about ten structures for both unit cells.…”

“…61 Ge-Ge and Ge-Sb bonds are found in those motifs, which is assumed to be due to disorder effects, since they are not present in the crystalline phases. Furthermore, a-GST shows volume expansion of 6%-7% compared with the m-GST phase, 10,36,62 and it has a higher energy ͑28-40 meV/at.͒ with respect to m-GST. 63 Based on EXAFS studies and Ge coordination change, Kolobov et al 54 suggested that the m-GST to a-GST transition is related to an umbrella flip of Ge atoms from octahedral to tetrahedral sites without the rupture of strong covalent bonds.…”

“…32 In this work, we will restrict ourselves to the m-GST phase due to the key role that it plays in optical storage applications. 3,5,[10][11][12][13][14] Experimental techniques such as high-resolution transmission electron microscopy ͑HRTEM͒, x-ray diffraction study ͑XRD͒, extended x-ray absorption fine-structure spectroscopy ͑EXAFS͒, and theoretical studies for the m-GST [27][28][29][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] phase have reported that the Te atoms occupy the anion sites and Ge, Sb, and the intrinsic vacancies ͑20% in GST͒ occupy the cation sites in the RS structure. Despite the seeming simplicity, the structural details of the m-GST structure are still under intense debate.…”

Temperature dependence of thermal properties of Ag8In14Sb55Te23 phase-change memory materials

“…The thermal properties of GST family were measured and studied in details, and the studies showed that there were common characteristics for different members in the GST family due to the distorted NaCl-type rock structures [21,22]. Accordingly, the thermal model of memory devices based on the GST family was established [6,23].…”

“…With the development of the phase-change memory, various materials were examined, and the materials of the best performances in terms of speed and stability were found to be GeSbTe (abbreviated as GST) family, such as Ge 2 Sb 2 Te 5 and Ge 1 Sb 4 Te 7 [4,9,16,17,[21][22][23], and AgInSbTe (abbreviated as AIST) family, such as Ag 3.4 [2,3,7,[11][12][13][14][15][24][25][26][27][28]. The thermal properties of GST family were measured and studied in details, and the studies showed that there were common characteristics for different members in the GST family due to the distorted NaCl-type rock structures [21,22].…”