Phase-dependent thermal conductivity of Ge1Sb4Te7 and N:Ge1Sb4Te7 for phase change memory applications

Shin, Sangwoo; Kim, Hyung Keun; Song, Jiwoon; Choi, Doo Jin; Cho, Hyung Hee

doi:10.1063/1.3294694

Cited by 36 publications

(19 citation statements)

References 20 publications

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“…Furthermore, it can be clearly observed from Fig. that all the peaks are well defined and clearly correspond to fcc diffraction planes for the films annealed at 440 K and to hcp planes for films annealed at 523 K and found to be in agreement with the literature .…”

Section: Resultssupporting

confidence: 87%

Direct evidence for phase transition in thin Ge₁Sb₄Te₇ films using in situ UV–Vis–NIR spectroscopy and Raman scattering studies

Sahu

Pandey

Manivannan

et al. 2016

Physica Status Solidi (b)

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Phase‐change materials (PCM) show remarkable property‐contrast from amorphous to crystalline phase that forms the basis for high‐speed non‐volatile memory device applications. Despite understanding the local structure and physical properties of these phases, a systematic study on the phase‐change behavior is essential. Here, we used in situ UV–Vis–NIR spectroscopic measurements to study a systematic evolution of optical band gap (Eg) and the local disorder described by Tauc parameter (B), for the temperatures from 90 to 480 K on amorphous and cubic phases of Ge1Sb4Te7 thin films. It has been found that the Eg of amorphous phase decreases with increasing temperature from 90 to 400 K, while the disorder as exemplified by B, increases owing to thermal vibrations. At 420 K, a rapid decrease in the Eg from 0.47 to 0.33 eV and also a sharp reduction of ∼13% in the value of B1/2 is observed evidencing the signature of amorphous‐to‐cubic phase transition. Furthermore, the hexagonal phase is more disordered compared to cubic phase. The Raman results are consistent with optical measurements, which indicate that the degree of disorder reduces from amorphous to cubic phase, while hexagonal phase with an increased disorder is attributed to elongated bonds.

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Section: Resultssupporting

confidence: 87%

Direct evidence for phase transition in thin Ge₁Sb₄Te₇ films using in situ UV–Vis–NIR spectroscopy and Raman scattering studies

Sahu

Pandey

Manivannan

et al. 2016

Physica Status Solidi (b)

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“…However, when the authors removed the contribution from electrons by employing the Wiedemann-Franz law (WFL), k l is reduced to around 0.7 Wm −1 K −1 [25], which is in good agreement with our calculated value. For GST147 at room temperature, our calculated lattice thermal conductivity is 1.38 Wm −1 K −1 , close to the experimental data of 1.2 Wm −1 K −1 [39], but being much higher than experimental data (0.49 Wm −1 K −1 ) from Shin and coworkers [40]. Obviously, there is large discrepancy among the different experimental results on the lattice thermal conductivity because of the different samples and measurement conditions.…”

Section: Resultssupporting

confidence: 75%

Lattice Thermal Conductivity of mGeTe•nSb2Te3 Phase-Change Materials: A First-Principles Study

Pan

Guo

2019

Crystals

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As the most promising materials for phase-change data storage, the pseudobinary mGeTe•nSb2Te3 (GST) chalcogenides have been widely investigated. Nevertheless, an in-depth understanding of the thermal-transport property of GST is still lacking, which is important to achieve overall good performance of the memory devices. Herein, by using first-principles calculations and Boltzmann transport theory, we have systematically studied the lattice thermal conductivity along the out of plane direction of both stable hexagonal and meta-stable rock-salt-like phases of GST, and good agreement with available experiments has been observed. It is revealed that with the increase of the n/m ratio, the lattice thermal conductivity of hexagonal GST increases due to the large contribution from the weak Te-Te bonding, while an inverse trend is observed in meta-stable GST, which is due to the increased number of vacancies that results in the decrease of the lattice thermal conductivity. The size effect on thermal conductivity is also discussed. Our results provide useful information to manipulate the thermal property of GST phase-change materials.

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“…The amorphous nature of the as-deposited film was unveiled by the lack of diffraction peaks. After annealing at 503 K, all the diffraction peak positions are clear and exhibit preferred (103), (106), (210) and (204) orientations as previously reported [17,18] revealing that all the annealed samples have crystallized into HCP phase. However, the peaks in S1-S3 are relatively less acuminate compared to those in S4-S6.…”

Section: Morphological and Structural Analysissupporting

confidence: 79%

Thickness dependence of a giant nonlinear saturable absorption response in GeSb₄Te₇ thin films

et al. 2018

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Nonlinear optical absorption (NOA) materials with large saturable absorption response and high damage threshold are useful for a variety of applications such as ultrafast nonlinear optical devices and laser mode lockers. In this study, a suite of GeSb 4 Te 7 thin films with different thicknesses were prepared, and the surface morphology, structure and linear optical absorption of these films were investigated in detail. Through an open aperture Z-scan technique with femtosecond pulses at 800 nm wavelength, it is found that effective NOA coefficient as high as −93 009 cm GW −1 can be achieved in GeSb 4 Te 7 thin films. Besides, GeSb 4 Te 7 thin films exhibit a giant and ultrafast third-order nonlinear optical saturable absorption response due to significant band filling effect. Especially, NOA response, coefficient and damage threshold can be well controlled by adjusting the film thickness. Both stability and efficiency can be acquired by thermal treatment. 2 1 --[9]. The crystalline Sb 2 Te 3 thin films themselves are used in the model structure and the layer mask, and also possesses giant saturation absorption (SA) caused by the saturated direct-band-gap transition [10]. Due to their fast phase change speed and giant NOA response, PCMs containing OPEN ACCESS RECEIVED

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Phase-dependent thermal conductivity of Ge1Sb4Te7 and N:Ge1Sb4Te7 for phase change memory applications

Cited by 36 publications

References 20 publications

Direct evidence for phase transition in thin Ge₁Sb₄Te₇ films using in situ UV–Vis–NIR spectroscopy and Raman scattering studies

Direct evidence for phase transition in thin Ge₁Sb₄Te₇ films using in situ UV–Vis–NIR spectroscopy and Raman scattering studies

Lattice Thermal Conductivity of mGeTe•nSb2Te3 Phase-Change Materials: A First-Principles Study

Thickness dependence of a giant nonlinear saturable absorption response in GeSb₄Te₇ thin films

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Phase-dependent thermal conductivity of Ge1Sb4Te7 and N:Ge1Sb4Te7 for phase change memory applications

Cited by 36 publications

References 20 publications

Direct evidence for phase transition in thin Ge1Sb4Te7 films using in situ UV–Vis–NIR spectroscopy and Raman scattering studies

Direct evidence for phase transition in thin Ge1Sb4Te7 films using in situ UV–Vis–NIR spectroscopy and Raman scattering studies

Lattice Thermal Conductivity of mGeTe•nSb2Te3 Phase-Change Materials: A First-Principles Study

Thickness dependence of a giant nonlinear saturable absorption response in GeSb4Te7 thin films

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Direct evidence for phase transition in thin Ge₁Sb₄Te₇ films using in situ UV–Vis–NIR spectroscopy and Raman scattering studies

Direct evidence for phase transition in thin Ge₁Sb₄Te₇ films using in situ UV–Vis–NIR spectroscopy and Raman scattering studies

Thickness dependence of a giant nonlinear saturable absorption response in GeSb₄Te₇ thin films