Thermal and electrical properties of the Ge:Sb:Te system by photoacoustic and Hall measurements

Yáñez‐Limón, J. M.; González‐Hernández, J.; Alvarado‐Gil, J. J.; Delgadillo, I.; Vargas, H.

doi:10.1103/physrevb.52.16321

Cited by 85 publications

(38 citation statements)

References 11 publications

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“…Several experimental works reported on the measurements of the bulk thermal conductivity of the prototypical GeSbTe phase change alloys [6][7][8][9] and the related binary compounds GeTe [10][11][12][13][14][15] and Sb 2 Te 3 [11,16]. These compounds have a relatively low lattice thermal conductivity in the crystalline phase which has been ascribed to a strong phonon scattering by disordered point defects.…”

Section: Introductionmentioning

confidence: 99%

“…In trigonal GeTe, vacancies in the Ge sublattice are responsible for the large spread of the measured thermal conductivity over the wide range of values 0.1-4.1 W m −1 K −1 [10][11][12][13][14][15]. The lattice thermal conductivity is very low (0.45 W m −1 K −1 ) [9] also in the hexagonal phase of Ge 2 Sb 2 Te 5 (GST), the crystalline phase stable at normal conditions, in which the vacancy concentration is much lower than that of the cubic phase.…”

Section: Introductionmentioning

confidence: 99%

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First-principles calculation of lattice thermal conductivity in crystalline phase change materials: GeTe, Sb2Te3 , and Ge2
Campi
¹
,
Paulatto
²
,
Fugallo
³

et al. 2017
Phys. Rev. B
108
17
85
0
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Thermal transport is a key feature for the operation of phase change memory devices which rest on a fast and reversible transformation between the crystalline and amorphous phases of chalcogenide alloys upon Joule heating. In this paper we report on the ab initio calculations of bulk thermal conductivity of the prototypical phase change compounds Ge 2 Sb 2 Te 5 and GeTe in their crystalline form. The related Sb 2 Te 3 compound is also investigated for the sake of comparison. Thermal conductivity is obtained from the solution of the Boltzmann transport equation with phonon scattering rates computed within density functional perturbation theory. The calculations show that the large spread in the experimental data on the lattice thermal conductivity of GeTe is due to a variable content of Ge vacancies which at concentrations realized experimentally can halve the bulk thermal conductivity with respect to the ideal crystal. We show that the very low thermal conductivity of hexagonal Ge 2 Sb 2 Te 5 of about 0.45 W m −1 K −1 measured experimentally is also resulting from disorder in the form of a random distribution of Ge/Sb atoms in one sublattice.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

First-principles calculation of lattice thermal conductivity in crystalline phase change materials: GeTe, Sb2Te3 , and Ge2
Campi
¹
,
Paulatto
²
,
Fugallo
³

et al. 2017
Phys. Rev. B
108
17
85
0
View full text Add to dashboard Cite

show abstract

“…18,19 Bending of crystal planes is of course greatly facilitated if the bonding between adjacent planes is relatively weak, e.g., when dominated by van der Waals forces like in graphite. Ab initio electronic structure calculations have shown that rhombohedral Ge 2 Sb 2 Te 5 can indeed be considered as a layered structure with the presence of a weak bonding ͑low electron density͒ between the GeTe and TeSbTe layers.…”

Section: B Transrotational Crystalsmentioning

confidence: 99%

On the crystallization of thin films composed of Sb3.6Te with Ge for rewritable data storage

Kooi

Hosson

2004

Journal of Applied Physics

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This article addresses the crystallization of amorphous Sb 3.6 Te films ͑40 nm thick͒ and 5 at. % Ge containing Sb 3.6 Te films ͑10, 20, and 40 nm thick͒ as studied with transmission electron microcopy using in situ annealing. These materials exhibit growth-dominated crystallization, in contrast to the usual Ge 2 Sb 2 Te 5 that shows nucleation-dominated crystallization. Particularly the crystal-growth velocity in these systems has been measured as a function of temperature from which the activation energy for growth can be derived. The strong effect of the 5 at. % Ge addition on the total crystallization behavior is revealed by the following four phenomena: Ge increases the crystallization temperature ͑from 95 to 150°C͒, increases the activation energy for growth ͑from 1.58 to 2.37 eV͒, increases the nucleation rate and decreases the growth anisotropy. The crystallites have a special transrotational structure and a mechanism responsible for the development of this special structure is delineated.

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“…The layered structure with many vacancies is beneficial to the low thermal conductivity and high electrical conductivity. 13 The GST compounds are expected to exhibit good thermoelectric properties attributing to the massive constituent elements, relatively weak coupling between the layers and large unit-cell dimensions, which lead to strong scattering of phones. In the present study, GST films were annealed at various temperatures to investigate the effect of the structural changes on the thermoelectric properties.…”

mentioning

confidence: 99%

Effect of Structural Change on Thermoelectric Properties of the Chalcogenide Ge₂Sb₂Te₅Thin Films

Hong

Yoon

2014

ECS J. Solid State Sci. Technol.

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Ge 2 Sb 2 Te 5 (GST) films grown onto SiO 2 (250 nm)/Si substrate at room temperature were annealed at various temperatures to investigate the structural variations. The GST films changed from amorphous to face-centered cubic (FCC) and hexagonal closed packed (HCP) crystalline phases as the annealing temperature increases and the samples annealed at 380 • C showed co-existence of the FCC and the HCP. Samples annealed at 380 • C showed the highest charge carrier concentration, the lowest resistivity, and the highest power factor. © The Author ( Highly efficient thin thermoelectric films have recently gained acceptance for potential applications in the microelectronics industry as sensors, microcoolers, and as low-power generators.1,2 Thermoelectric transport can have a large impact on the performance of semiconductor devices and related nanostructures.3-5 Compared with the conventional mechanical devices, thermoelectric devices have the advantages such as maintenance-free, better transient response. 6,7 The primary candidate technology for miniaturizing thermoelectric devices is to apply semiconductor-processing technologies including thin film fabrication. The efficiency of conversion is described by the dimensionless, thermoelectric figure-of-merit, ZT = S 2 T/ρκ, where S is the Seebeck coefficient, T is the absolute temperature, ρ is the electrical resistivity, and κ is the total thermal conductivity. A high ZT may be achieved by reducing κ and by enhancing the thermoelectric power factor, P = S 2 /ρ. The interrelated Seebeck coefficient, electrical conductivity, and thermal conductivity make it difficult to improve one transport property without affecting the others. 8 The key issue of micro-thermoelectric devices is how to fabricate thin films with high performance by semiconductor-processing technologies.Various chalcogenide materials reported that the holes are responsible for their positive Seebeck coefficient. 9 The Seebeck coefficient is strongly depended on the phase and the processing conditions. The Seebeck coefficients for the Ge 2 Sb 2 Te 5 (GST) films of various thicknesses and for the phase purity such as amorphous and crystalline phases have been reported. 10,11 There are two types of crystal structure in the GST compounds. One is the metastable rocksalt structure with Te atoms occupying sites on one face-centered-cubic (FCC) sublattice, and Ge and Sb randomly forming the other FCC sublattice. The other is the hexagonal structure (HCP), which is composed of Te layers forming a complicated cubic close packed structure with Ge and Sb atoms randomly occupying the octahedral interstices. Friedrich et al. reported that the temperature dependent measurements of the electrical resistance have been employed to study structural changes in direct current (dc) sputtered GST films.12 Using the films with a thickness between 80 and 250 nm, they reported that the pronounced changes of film resistance due to structural changes enabled a precise determination of transition temperature and activation energies. T...

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Thermal and electrical properties of the Ge:Sb:Te system by photoacoustic and Hall measurements

Cited by 85 publications

References 11 publications

First-principles calculation of lattice thermal conductivity in crystalline phase change materials: GeTe, Sb2Te3 , and Ge2
Campi
¹
,
Paulatto
²
,
Fugallo
³

et al. 2017
Phys. Rev. B
108
17
85
0
View full text Add to dashboard Cite

First-principles calculation of lattice thermal conductivity in crystalline phase change materials: GeTe, Sb2Te3 , and Ge2
Campi
¹
,
Paulatto
²
,
Fugallo
³

et al. 2017
Phys. Rev. B
108
17
85
0
View full text Add to dashboard Cite

On the crystallization of thin films composed of Sb3.6Te with Ge for rewritable data storage

Effect of Structural Change on Thermoelectric Properties of the Chalcogenide Ge₂Sb₂Te₅Thin Films

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Thermal and electrical properties of the Ge:Sb:Te system by photoacoustic and Hall measurements

Cited by 85 publications

References 11 publications

First-principles calculation of lattice thermal conductivity in crystalline phase change materials: GeTe, Sb2Te3 , and Ge2Campi1, Paulatto2, Fugallo3 et al. 2017Phys. Rev. B10817850View full textAdd to dashboardCite

First-principles calculation of lattice thermal conductivity in crystalline phase change materials: GeTe, Sb2Te3 , and Ge2Campi1, Paulatto2, Fugallo3 et al. 2017Phys. Rev. B10817850View full textAdd to dashboardCite

On the crystallization of thin films composed of Sb3.6Te with Ge for rewritable data storage

Effect of Structural Change on Thermoelectric Properties of the Chalcogenide Ge2Sb2Te5Thin Films

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First-principles calculation of lattice thermal conductivity in crystalline phase change materials: GeTe, Sb2Te3 , and Ge2
Campi
¹
,
Paulatto
²
,
Fugallo
³

et al. 2017
Phys. Rev. B
108
17
85
0
View full text Add to dashboard Cite

First-principles calculation of lattice thermal conductivity in crystalline phase change materials: GeTe, Sb2Te3 , and Ge2
Campi
¹
,
Paulatto
²
,
Fugallo
³

et al. 2017
Phys. Rev. B
108
17
85
0
View full text Add to dashboard Cite

Effect of Structural Change on Thermoelectric Properties of the Chalcogenide Ge₂Sb₂Te₅Thin Films