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Константинов, П. П.; Shelimova, L. E.; Avilov, E. S.; Kretova, M. A.; Zemskov, V. S.

doi:10.1023/a:1017613804472

Cited by 72 publications

(39 citation statements)

References 9 publications

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“…Our calculation showed that the cubic phase has almost the same band structure as the hexagonal phase for a given layer sequence ͑not shown here͒. This implies that the contrasting electrical properties of cubic and hexagonal phases 10,11 can be attributed to a different tendency of layer sequences in the two structures. One caveat is that in this study, as the vacancies are assumed to be ordered for both crystalline phases, not only the layer sequence but also the disordering in vacancy distribution can significantly affect the electronic structures.…”

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confidence: 58%

“…As for the electrical properties, the Hall measurement 10,11 showed p-type conduction with a carrier concentration of about 10 20 / cm 3 for both cubic and hexagonal phases. The temperature dependence of the conductivity, on the other hand, indicated that the hexagonal phase exhibits a metallic characteristic, while the cubic phase behaves like a semiconductor.…”

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confidence: 94%

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Ab initiostudies of structural and electronic properties of the crystallineGe2Sb2Te5

Lee

Jhi

2008

Phys. Rev. B

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We study the atomic structure and the electronic and optical properties of Ge 2 Sb 2 Te 5 in two different crystalline states of cubic and hexagonal structures with the use of ab initio pseudopotential density functional method. It is found that electronic and atomic structures are very sensitive to the layer sequence in the two phases. The proximity of vacancy layer to Ge layer leads to the splitting of Ge-Te bond length, which, in turn, affects the electronic and optical properties. Phase-change random access memory ͑PRAM͒ is one of the most promising candidates for the next generation nonvolatile memories. The 225 phase ͑Ge 2 Sb 2 Te 5 or GST in short͒ is the simplest and most promising and has thus been extensively studied. The GST is known to undergo a series of structural transitions at elevated temperature from nonconducting amorphous ͑a͒ to metastable cubic ͑c͒ and to a more stable hexagonal above 300°C. Pulse current-driven melting ͑above ϳ600°C͒ and quenching switch the crystalline phase to high-resistive amorphous phase. The rapid and reversible cycles between the amorphous and crystalline structures lead to the resistivity change that reads as the on-off state of PRAM ͑Ref. 1 and references therein͒. Recently, the a ↔ c transition has actively been investigated by extended x-ray absorption fine structure ͑EXAFS͒.1-3 The flip of Ge atoms from octahedral to tetrahedral sites was proposed as a mechanism for the rapid a ↔ c transition, 2 but detailed atomic structures in the process are still yet to be known. The metastable cubic phase has a rocksalt structure, in which cations ͑Ge, Sb͒ and vacancies randomly occupy the fcc sublattice and Te wholly occupies the other sublattice. 4 An intermediate state during the transformation to the stable hexagonal phase was also observed with a rearrangement of cations to form ordered layers. showed p-type conduction with a carrier concentration of about 10 20 / cm 3 for both cubic and hexagonal phases. The temperature dependence of the conductivity, on the other hand, indicated that the hexagonal phase exhibits a metallic characteristic, while the cubic phase behaves like a semiconductor. This observation seems inconsistent with the measured optical gap of 0.5 eV for both phases.10,12 The vacancies are considered to play an important role in the electrical conduction, 12,13 but the conduction mechanism is not yet clearly understood. One possible origin of the different electrical properties is the ordered ͑disordered͒ arrangement of vacancies in hexagonal ͑cubic͒ phase and the layer sequence. In this Brief Report, we report the atomic structures and electronic and optical properties of GST with the use of ab initio pseudopotential density functional method. Of particular interest is the structure and layer-sequence dependence of these properties.For the total energy calculations, the Vienna ab initio simulation package ͑VASP͒ 14 is used. The exchange correlation of electrons is treated within the generalized gradient approximation ͑GGA͒ in the form of Perdew-Wang 19...

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confidence: 58%

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confidence: 94%

Ab initiostudies of structural and electronic properties of the crystallineGe2Sb2Te5

Lee

Jhi

2008

Phys. Rev. B

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“…[ 6 ] Hall effect and thermopower measurements agree that crystalline GeSbTe fi lms are p type. [4][5][6][7]16,26,27 ] Moreover, there is little doubt that Ge 1 Sb 2 Te 4 fi lms which have been annealed at temperatures above 250 °C can be regarded as ordinary degenerate semiconductors, where the Fermi level intersects the valence band and the wave functions in the vicinity of the Fermi level are extended Bloch waves. [ 6 ] Bahl and Chopra [ 28 ] pointed out that the electrical properties of crystalline (rhombohedral) GeTe can be readily understood by a simple model consisting of a parabolic and isotropic valence band maximum.…”

Section: Electrical Propertiesmentioning

confidence: 99%

Disorder‐Induced Localization in Crystalline Pseudo‐Binary GeTe–Sb₂Te₃ Alloys between Ge₃Sb₂Te₆ and GeTe

Jost

Völker

Poitz

et al. 2015

Adv Funct Materials

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Disorder has a tremendous impact on charge transport in crystalline compounds on the pseudo-binary line between Sb 2 Te 3 and GeTe. Directly after crystallization, the pronounced disorder on the cation sublattice renders crystalline Ge 1 Sb 2 Te 4 -a composition with a carrier density of the order of 10 20 cm-an Anderson insulator. Annealing, however, induces the reduction of disorder and eventually triggers an insulator-to-metal transition. This study presents data on the electrical properties, the optical conductivity, and structural properties of the pseudo-binary compositions between Ge 3 Sb 2 Te 6 and GeTe. In contrast to the preceding investigations, which rely on the annealing temperature for tuning the electrical properties, this study elucidates the impact of stoichiometry and demonstrates that the stoichiometry may be employed as an alternative control parameter for the metal-to-insulator transition. The combination of annealing temperature and stoichiometry, therefore, provides a rich playground for tailoring disorder and, as a consequence, the transport of charge.

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“…A large number of new materials with promising thermoelectric properties have been investigated. These include, for example, filled skutterudites, 1,2 clathrates, 3 pentatellurides, 4 half-Heusler-alloys, [5][6][7] ternary and quaternary heavy metal chalcogenides, [8][9][10][11] and layered cobalt oxides. [12][13][14] In addition, the efficiency of well-known thermoelectric materials such as Bi 2 Te 3 and PbTe has been improved dramatically by incorporation into nanostructured devices.…”

Section: Introductionmentioning

confidence: 99%

Structures and thermoelectric properties of the infinitely adaptive series(Bi2)m(Bi2Te3
Bos
¹
,
Zandbergen
²
,
Lee
³

et al. 2007
Phys. Rev. B
194
14
129
1
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Cited by 72 publications

References 9 publications

Ab initiostudies of structural and electronic properties of the crystallineGe2Sb2Te5

Ab initiostudies of structural and electronic properties of the crystallineGe2Sb2Te5

Disorder‐Induced Localization in Crystalline Pseudo‐Binary GeTe–Sb₂Te₃ Alloys between Ge₃Sb₂Te₆ and GeTe

Structures and thermoelectric properties of the infinitely adaptive series(Bi2)m(Bi2Te3
Bos
¹
,
Zandbergen
²
,
Lee
³

et al. 2007
Phys. Rev. B
194
14
129
1
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Untitled

Cited by 72 publications

References 9 publications

Ab initiostudies of structural and electronic properties of the crystallineGe2Sb2Te5

Ab initiostudies of structural and electronic properties of the crystallineGe2Sb2Te5

Disorder‐Induced Localization in Crystalline Pseudo‐Binary GeTe–Sb2Te3 Alloys between Ge3Sb2Te6 and GeTe

Structures and thermoelectric properties of the infinitely adaptive series(Bi2)m(Bi2Te3Bos1, Zandbergen2, Lee3 et al. 2007Phys. Rev. B194141291View full textAdd to dashboardCite

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Disorder‐Induced Localization in Crystalline Pseudo‐Binary GeTe–Sb₂Te₃ Alloys between Ge₃Sb₂Te₆ and GeTe

Structures and thermoelectric properties of the infinitely adaptive series(Bi2)m(Bi2Te3
Bos
¹
,
Zandbergen
²
,
Lee
³

et al. 2007
Phys. Rev. B
194
14
129
1
View full text Add to dashboard Cite