Evidence of Germanium precipitation in phase-change Ge1−xTex thin films by Raman scattering

Gourvest, E.; Lhostis, S.; Kreisel, J.; Armand, M.; Maîtrejean, S.; Roule, A.; Vallée, C.

doi:10.1063/1.3186077

Cited by 38 publications

(21 citation statements)

References 13 publications

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“…The apparent crystallization temperature was defined as the temperature at which half of the sample was crystallized [19]. The apparent crystallization temperatures observed in this study are higher than values reported by others, as determined from optical reflectivity measurements [20,21]. This is expected as all the films here are Te-rich in composition.…”

Section: Resultscontrasting

confidence: 40%

Impact of deposition conditions on the crystallization kinetics of amorphous GeTe films

et al. 2015

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The speed at which phase change memory devices can operate depends strongly on the crystallization kinetics of the amorphous phase. To better understand factors that affect the crystallization rate, we have investigated crystallization of GeTe films as a function of their deposition temperatures and deposition rates, using X-ray synchrotron radiation and Raman spectroscopy. As-deposited films were found to be fully amorphous under all conditions, even though films deposited at higher temperatures and lower rates experienced lower effective quench rates. Non-isothermal transformation curves show that the apparent crystallization temperature of GeTe films decreases with increasing deposition temperature and decreasing deposition rate. It was found that this correlates with a decrease in the activation energy for nucleation (calculated using Kissinger's analysis), while the activation energy for crystal growth remained unaffected. From Raman spectroscopy measurements, it was found that increasing the deposition temperature or decreasing the deposition rate, and therefore the effective quench rate, reduces the number of homopolar Te-Te bonds and thereby reduces the barrier to crystal nucleation.

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Section: Resultscontrasting

confidence: 40%

Impact of deposition conditions on the crystallization kinetics of amorphous GeTe films

et al. 2015

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“…1) show one endothermic glass transition peak and different exothermic crystallization peaks. In the composition range 1 ≤ x < 3, Si 15 Te 85-x Ge x glasses show two crystallization reactions at temperatures T c1 and T c2 respectively whereas, in the composition range 3 ≤ x ≤ 11 two crystallization reactions take place at single crystallization temperature, say, T c1 . It is also seen from Fig.…”

Section: Resultsmentioning

confidence: 99%

“…12 In many of the chalcogenide systems, the coordination numbers of Si, Ge and Te obey the Mott's 8-N rule, where N is number of valance electrons, 13 therefore, in the present Si-Te-Ge glassy system, the coordination numbers of Si, Ge and Te can be safely assumed to be 4, 4 and 2 respectively. If we consider Si 15 Te 74 Ge 11 sample for the highest dopant concentration (x = 11), there will be a total of (15+11) × 4 = 104 Si + Ge bonds available in glassy network but at the same time 74 × 2 = 148 Te bonds available to form glassy network with Si and Ge atoms and among themselves. Since the glass samples studied in the present work are Te-rich, there will be a large number of Te-Te chains presented in the glassy network.…”

Section: Gete-imentioning

confidence: 99%

“…The peak B can be attributed to the A 1 mode, peaks A and C to the E TO modes and peak D to the E LO mode of Te-Te chain. 14 The peaks J, 15 G and H (which is merged in peak B) can be assigned to the amorphous-GeTe phase. 16 The peak F can be assigned to the symmetric stretching mode of the edge-sharing GeTe 4 tetrahedra.…”

Section: Gete-imentioning

confidence: 99%

“…7,8 In view of various potential applications of ChGs, a precise knowledge of crystalline phases is necessary for the development of suitable phase-change, erasable electrical/optical storage media. In the present work, the thermal behavior of Si 15 Te 85-x Ge x glasses of a wide composition range (1 ≤ x ≤ 11) has been investigated using Alternating Differential Scanning Calorimetry (ADSC). X-ray diffraction (XRD) studies have been performed to confirm the amorphous nature of as-prepared glasses and to identify the stable crystalline phases presented at different temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Observation of high pressure o-GeTe phase at ambient pressure in Si-Te-Ge glasses

Gunti

Asokan

2012

AIP Advances

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Te-rich Si15Te85-xGex (1 ≤ x ≤ 11) glasses are found to exhibit an anomalous phase separations with germanium composition. The structural transformation of o-GeTe crystalline phase from o-GeTe with a = 11.76 Å, b = 16.59 Å, c = 17.44 Å, to high pressure o-GeTe with a new reduced lattice parameters a = 10.95 Å, b = 4.03 Å, c = 4.45 Å, is observed at Tc3 in the composition range 6 ≤ x ≤ 11. Raman studies support the possible existence of high pressure o-GeTe phase which is observed in X-ray diffraction experiments

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Structural and optical properties of phase‐change amorphous and crystalline Ge_1 − xTe_x (0 < x < 1) thin films

Park

Song

Yoon

et al. 2012

Physica Status Solidi (a)

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Ge1 − xTex thin films were grown using thermal coevaporation deposition. The dielectric functions and the phonon modes of amorphous (a‐) and crystalline (c‐) Ge1 − xTex films were measured using spectroscopic ellipsometry and Raman spectroscopy in order to investigate electronic and vibrational properties of these alloys. Using the second derivative spectra of the dielectric functions of a‐Ge1 − xTex alloys and the standard critical point (SCP) model, we obtained optical transition energies for the a‐Ge1 − xTex alloys. The optical transition energies were not only consistent with the density of states (DOS) reported in the literature, but also provided more detailed structures for the joint density of states (JDOS) of a‐Ge1 − xTex. magnified imageThe second derivative spectra of d2ε(E)/dE2 for amorphous GeTe. The transition energies were estimated using SCP model (short arrows) and were compared to those of photoemission spectroscopy from literature (long arrows).

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Evidence of Germanium precipitation in phase-change Ge1−xTex thin films by Raman scattering

Cited by 38 publications

References 13 publications

Impact of deposition conditions on the crystallization kinetics of amorphous GeTe films

Impact of deposition conditions on the crystallization kinetics of amorphous GeTe films

Observation of high pressure o-GeTe phase at ambient pressure in Si-Te-Ge glasses

Structural and optical properties of phase‐change amorphous and crystalline Ge_1 − xTe_x (0 < x < 1) thin films

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Evidence of Germanium precipitation in phase-change Ge1−xTex thin films by Raman scattering

Cited by 38 publications

References 13 publications

Impact of deposition conditions on the crystallization kinetics of amorphous GeTe films

Impact of deposition conditions on the crystallization kinetics of amorphous GeTe films

Observation of high pressure o-GeTe phase at ambient pressure in Si-Te-Ge glasses

Structural and optical properties of phase‐change amorphous and crystalline Ge1 − xTex (0 < x < 1) thin films

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Structural and optical properties of phase‐change amorphous and crystalline Ge_1 − xTe_x (0 < x < 1) thin films