Peierls Instabilities in Covalent Structures

Gaspard, Jean-Pierre; Marinelli, F.; Pellégatti, A.

doi:10.1209/0295-5075/3/10/007

Cited by 61 publications

(44 citation statements)

References 6 publications

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“…74,75 Thus, our results support a RS-type structure for m-GST in which the Ge, Sb, and Te atoms are slightly shifted from their high-symmetry positions in a correlated manner, confirming the Kolobov et al 37 suggestion.…”

Section: A Metastable Gst Crystalline Phasesupporting

confidence: 87%

Atomistic origins of the phase transition mechanism in Ge2Sb2Te5

Silva

Walsh

Wei

et al. 2009

Journal of Applied Physics

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Tricritical behavior of the RI-RV rotator phase transition in a mixture of alkanes with nanoparticles J. Chem. Phys. 135, 134505 (2011) Pressure-induced amorphization in mayenite (12CaO·7Al2O3) J. Chem. Phys. 135, 094506 (2011) Influence of Al2O3 crystallization on band offsets at interfaces with Si and TiNx Appl. Phys. Lett. 99, 072103 (2011) Temperature induced transition from hexagonal to circular pits in graphite oxidation by O2 Appl. Phys. Lett. 99, 044102 (2011) Phase transformation of Ho2O3 at high pressure J. Appl. Phys. 110, 013526 (2011) Additional information on J. Appl. Phys. The fast and reversible phase transition mechanism between crystalline and amorphous phases of Ge 2 Sb 2 Te 5 has been in debate for several years. Through employing first-principles density functional theory calculations, we identify a direct structural link between the metastable crystalline and amorphous phases. The phase transition is driven by the displacement of Ge atoms along the rocksalt ͓111͔ direction from stable octahedron to high energy unstable tetrahedron sites close to the intrinsic vacancy regions, which generates a high energy intermediate phase between metastable and amorphous phases. Due to the instability of Ge at the tetrahedron sites, the Ge atoms naturally shift away from those sites, giving rise to the formation of local-ordered fourfold motifs and the long-range structural disorder. Intrinsic vacancies, which originate from Sb 2 Te 3 , lower the energy barrier for Ge displacements, and hence, their distribution plays an important role in the phase transition. The high energy intermediate configuration can be obtained experimentally by applying an intense laser beam, which overcomes the thermodynamic barrier from the octahedron to tetrahedron sites. The high figure of merit of Ge 2 Sb 2 Te 5 is achieved from the optimal combination of intrinsic vacancies provided by Sb 2 Te 3 and the instability of the tetrahedron sites provided by GeTe.

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Section: A Metastable Gst Crystalline Phasesupporting

confidence: 87%

Atomistic origins of the phase transition mechanism in Ge2Sb2Te5

Silva

Walsh

Wei

et al. 2009

Journal of Applied Physics

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“…[41][42][43] To further rationalize the atomic arrangements and link them to the electronic properties in GST, we analyzed the Peierls-like distortion (PD), which refers to the displacement of a sublattice away from the "central position" in order to lower the electronic energy, giving rise to collinear short-long bond pairs and entailing the opening of the bandgap. [44][45][46] Most crystalline chalcogenides contain some degrees of PD, and pairs of collinear short-long bonds indicative of PD occur in liquid and amorphous PCMs as well. [47,48] In general, the stronger the PD is, the larger the bandgap is expected to be.…”

Section: Aimd Results and Discussionmentioning

confidence: 99%

Reversing the Resistivity Contrast in the Phase‐Change Memory Material GeSb₂Te₄ Using High Pressure

Wang

et al. 2015

Adv Elect Materials

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Phase‐change memory devices distinguish “1” and “0” states by the electrical contrast between the amorphous and the crystalline phases. Under ambient conditions, the amorphous phase normally exhibits a higher resistivity, exceeding its crystalline counterpart by 2–5 orders of magnitude. Here, however, it is demonstrated that such pronounced resistivity contrast is remarkably reduced and even reversed with increasing hydrostatic‐like pressure in the prototypical phase‐change material GeSb2Te4 (GST). This anomalous resistivity reversal originates from the differences in the pressure‐induced atomic rearrangement of these two phases, as revealed by ab initio molecular dynamics simulations. Specifically, a low to medium pressure (<7 GPa) primarily compresses the bonds in crystalline GST without significantly displacing the atoms and vacancies off the lattice sites. As a result, only relatively small changes in the band structure are induced. In contrast, in amorphous GST, the fraction of voids changes drastically with pressure and the Peierls‐like distortion is greatly reduced, yet the average bond length remains almost constant. These effects eventually turn the semiconducting glass into a metallic one. Our work reveals distinct behaviors of amorphous and crystalline phase‐change materials under stress, shedding light on the mechanisms of electronic transport in different phases, and thus may have important implications on the design of phase‐change memory devices.

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“…So, the model describes the forming of a semiconductor gap in PbX under pressure. Peierls structures have a lower density than undistorted lattices, so, a certain pressure ought to metallize the substances [25]. The semiconductor-metal phase transformations observed in PbX (Fig.…”

Section: Resultsmentioning

confidence: 99%

Semiconductor–metal transitions in lead chalcogenides at high pressure

Ovsyannikov

Shchennikov

Popova

et al. 2003

Physica Status Solidi (b)

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PACS 71.30.+h, 72.20.MyThe results of thermoelectric power (S) measurements of the lead chalcogenides PbS, PbSe, and PbTe at the initial NaCl-phase, as high-pressure semiconductors (above 2 -6 GPa), and at metal phases (above 10 -15 GPa) are presented. Phase transitions are discussed in terms of the model of Peierls distortion of lattice. IntroductionThe lead chalcogenides PbS, PbSe, and PbTe are narrow gap semiconductors with forbidden energy gaps of 0.286 eV, 0.16 eV, and 0.19 eV, respectively [1−3]. At high pressure P ∼ 2 −6 GPa these compounds undergo a phase transformation from the NaCl-to the GeS-type lattice [4−10] with about a two-fold increase of the lattice parameter a [5]. The resistivity of PbX (X is S, Se, or Te) compounds abruptly rises at the phase transition [4−8] similar to mercury chalcogenides, but contrary to most of other semiconductors. At pressures above ∼15 GPa further structural phase transitions were observed into the CsCl-type cubic lattice [9,10]. The jumps of the electrical resistance R during the first transitions [4−8] and the drop of R at the second one allows to suggest that structural changes are accomplished by electronic "semiconductor-metal" phase transitions [6,7,10]. Thermoelectric properties of new phases, which are capable to clarify the electronic structure [11], are unknown. The aim of the present work was the investigation of the thermoelectric power S of high pressure phases of PbX compounds.

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Peierls Instabilities in Covalent Structures

Cited by 61 publications

References 6 publications

Atomistic origins of the phase transition mechanism in Ge2Sb2Te5

Atomistic origins of the phase transition mechanism in Ge2Sb2Te5

Reversing the Resistivity Contrast in the Phase‐Change Memory Material GeSb₂Te₄ Using High Pressure

Semiconductor–metal transitions in lead chalcogenides at high pressure

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Peierls Instabilities in Covalent Structures

Cited by 61 publications

References 6 publications

Atomistic origins of the phase transition mechanism in Ge2Sb2Te5

Atomistic origins of the phase transition mechanism in Ge2Sb2Te5

Reversing the Resistivity Contrast in the Phase‐Change Memory Material GeSb2Te4 Using High Pressure

Semiconductor–metal transitions in lead chalcogenides at high pressure

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Reversing the Resistivity Contrast in the Phase‐Change Memory Material GeSb₂Te₄ Using High Pressure