Publisher’s Note: Glass Transitions, Semiconductor-Metal Transitions, and Fragilities in 
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, Sb) Liquid Alloys: The Difference One Eleme

Wei, Shuai; Coleman, Garrett J.; Lucas, Pierre; Angell, C. Austen

doi:10.1103/physrevapplied.8.049901

Cited by 16 publications

(42 citation statements)

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“…We remark that the value T M −SC =800 K inferred from rVV10 simulation is actually equal to the estimate given in Ref. 21 where it is assumed that the T M −SC corresponds to a maximum in the specific heat. The temperature for the maximum in the specific heat for GeTe was obtained in turn by extrapolating to the GeTe composition the corresponding values known experimentally for other GeTe x alloys richer in tellurium.…”

Section: B Getesupporting

confidence: 69%

“…The temperature for the maximum in the specific heat for GeTe was obtained in turn by extrapolating to the GeTe composition the corresponding values known experimentally for other GeTe x alloys richer in tellurium. 21…”

Section: B Getementioning

confidence: 99%

“…18 In this context, a precise location of the M-SC transition is also of interest because it has been suggested that T M −SC might control a strong-to-fragile crossover in the temperature dependence of the viscosity. 21 In turn, a strong-to-fragile transition sufficiently close to T g would guarantee a fast crystallization for the reasons outlined above and at the same time a higher stability of the amorphous phase whose aging propensity is usually larger the higher is the fragility close to T g . 22,23 Previous DFT molecular dynamics (MD) simulations of Ge 2 Sb 2 Te 5 8 and GeTe 9 have shown a deepening of the pseudogap at E F upon cooling from temperatures slightly above to slightly below T m .…”

Section: Introductionmentioning

confidence: 99%

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Metal-semiconductor transition in the supercooled liquid phase of the Ge2Sb2Te5 and GeTe compounds

Cobelli

Dragoni

Caravati

et al. 2021

Phys. Rev. Materials

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The Ge2Sb2Te5 and GeTe compounds are of interest for applications in phase change memories. In the reset process of the memory the crystal is rapidly brought above the melting temperature Tm by Joule heating and then the liquid phase rapidly cools down leading to the formation of the amorphous phase. Since the liquid above Tm is metallic and the amorphous phase is semiconducting a semiconductor-to-metal transition occurs in the supercooled liquid. Based on density functional simulations, we estimated the metal-semiconductor transition temperature TM−SC by monitoring the opening of a band gap in the supercooled liquid phase. Due to previous evidence on the importance of the van der Waals (vdW) interaction in describing the liquid phase of these materials, we used both the revised Vydrov-van Voorhis functional which includes vdW non-local interactions and the Perdew-Burke-Ernzerhof functional without vdW corrections. The estimated TM−SC is about 100-150 K higher with the former than with the latter framework for both compounds. By including vdW interactions the estimated TM−SC is closer to Tm than to the glass transition temperature for both systems. The analysis of the structural properties as a function of temperature suggests a correlation between the metal-semiconductor transition and a Peierls distortion. However, the data support more a continuous structural transformation than the presence of a first order liquid-liquid phase change associated the metal-semiconductor transition.

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Section: B Getesupporting

confidence: 69%

Section: B Getementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Metal-semiconductor transition in the supercooled liquid phase of the Ge2Sb2Te5 and GeTe compounds

Cobelli

Dragoni

Caravati

et al. 2021

Phys. Rev. Materials

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“…Among chalcogenide ternary systems, the Ge-Sb-Te displays probably one of the smallest GFR (Fig. 1) that is limited to Sb-poor compositions close to the eutectic GeTe 6 where bulk glasses can be formed [15][16][17][18][19][20]. This is due, in part, to the large fragilities which are characteristic of liquids having small viscosities even in the deep supercooled state so that activation barriers for crystallization are low.…”

Section: Introductionmentioning

confidence: 99%

Obtaining glasses in the extremely crystallizing Ge–Sb–Te phase change material

Piarristeguy

Micoulaut²,

Escalier³

et al. 2021

Journal of Non-Crystalline Solids

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Using thermal co-evaporation techniques, we show that various glassy compositions can be obtained along the Ge x Sb x Te 100-2x join in the ternary Ge-Sb-Te system which is known to display dramatic crystallization tendencies. Earlier attempts to produce bulk glasses have been limited to Sb-poor compositions close to the eutectic GeTe 6 . Results indicate a weak variation of T g with composition x and also a thermal stability that is weak for most systems, and especially for compositions close to the domain where Ge 2 Sb 2 Te 5 can be formed. Our results are put in perspective with other network-forming chalcogenides and the T g variation suggests the preferential formation of Te-Sb-Te, at variance with isochemical compounds such as Ge-Sb-Se. Data are discussed within the framework of topological based approaches which not only indicate that optimal glass formation is achieved for compositions satisfying the Maxwell stability criterion but also predict a flexible to rigid transition at x = 8.5%. Most of our glasses could be formed around this composition.

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“…There is the additional advantage that the nature and strength of the homopolar Se-Se and heteropolar Ge/As-Se bonds in this system are similar, which ensures that their effects on the network rigidity can be considered comparable. Although other chalcogenide systems, i.e., the sulfides and the tellurides, share similarities in the compositional variation of their physical properties, the increasingly ionic behavior in sulfides and metallic behavior in tellurides result in significant differences in the nature of the homopolar and heteropolar bonds (Wei et al, 2017). The analysis of S-rich glasses is further complicated by the presence of S 8 rings that do not participate in the network (Zhu et al, 2018).…”

Section: Connection With Experimentsmentioning

confidence: 99%

Topological Constraint Theory for Network Glasses and Glass-Forming Liquids: A Rigid Polytope Approach

Sen

Mason

2019

Front. Mater.

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A variation of the topological constraint theory is proposed where an atomic network is modeled as a collection of rigid polytopes, and which explicitly distinguishes the bond angle constraints as well as rigid bond angles from flexible ones. The proposed theory allows for direct quantitative estimation of the fraction f of zero-frequency or floppy modes of the network. A preliminary model is proposed to connect the theory to the two key experimental observables that characterize glass-forming liquids, i.e., the glass transition temperature T g and fragility m. The predicted values are tested against the literature data available for binary and ternary chalcogenides in the Ge-As-Se system. The T g is related to f in this model by the activation entropy associated with the bond scission-renewal dynamics that is at the heart of transport and relaxation in glass-forming liquids. On the other hand, the large and temperature-dependent conformational entropy contribution of the 1-polytopes, i.e., the selenium chain elements in these chalcogenide glass-forming liquids, plays a key role in controlling the variation of m with f.

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Publisher’s Note: Glass Transitions, Semiconductor-Metal Transitions, and Fragilities in Ge−V−Te ( V=As , Sb) Liquid Alloys: The Difference One Eleme

Cited by 16 publications

References 0 publications

Metal-semiconductor transition in the supercooled liquid phase of the Ge2Sb2Te5 and GeTe compounds

Metal-semiconductor transition in the supercooled liquid phase of the Ge2Sb2Te5 and GeTe compounds

Obtaining glasses in the extremely crystallizing Ge–Sb–Te phase change material

Topological Constraint Theory for Network Glasses and Glass-Forming Liquids: A Rigid Polytope Approach

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