Density change upon crystallization of Ga-Sb films

Putero, Magali; Coulet, Marie‐Vanessa; Müller, Christophe; Cohen, Guy; Hopstaken, Marinus; Baehtz, Carsten; Raoux, Simone

doi:10.1063/1.4901321

Cited by 20 publications

(19 citation statements)

References 27 publications

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“…This indicates a continuous structure deformation with temperature. The decrease in mass density upon crystallisation anomaly, which was observed for films with more than 6 at.% oxygen is by no means common, and there are only a few reports of similar effects in the literature: Ge-rich Ge-Sb35, Sb-rich Ga-Sb36, and Cu-Ge-Te37 alloys.…”

Section: Discussionmentioning

confidence: 99%

A zero density change phase change memory material: GeTe-O structural characteristics upon crystallisation

Zhou

Dong

Zhang

et al. 2015

Sci Rep

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Oxygen-doped germanium telluride phase change materials are proposed for high temperature applications. Up to 8 at.% oxygen is readily incorporated into GeTe, causing an increased crystallisation temperature and activation energy. The rhombohedral structure of the GeTe crystal is preserved in the oxygen doped films. For higher oxygen concentrations the material is found to phase separate into GeO2 and TeO2, which inhibits the technologically useful abrupt change in properties. Increasing the oxygen content in GeTe-O reduces the difference in film thickness and mass density between the amorphous and crystalline states. For oxygen concentrations between 5 and 6 at.%, the amorphous material and the crystalline material have the same density. Above 6 at.% O doping, crystallisation exhibits an anomalous density change, where the volume of the crystalline state is larger than that of the amorphous. The high thermal stability and zero-density change characteristic of Oxygen-incorporated GeTe, is recommended for efficient and low stress phase change memory devices that may operate at elevated temperatures.

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Section: Discussionmentioning

confidence: 99%

A zero density change phase change memory material: GeTe-O structural characteristics upon crystallisation

Zhou

Dong

Zhang

et al. 2015

Sci Rep

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“…Recently, Te-free compounds, including CSb 8 , GaSb 9 , GeSb 10 , ZnSb 11 , NSb 12 and OSb 13 , have been widely used as phase-change materials because of their growth-dominated crystallization mechanism and rapid amorphous-to-crystalline transitions. Binary Zn-Sb systems, such as ZnSb and β-Zn 4 Sb 3 , are promising p-type materials 14 .…”

Section: Introductionmentioning

confidence: 99%

Suppression for an intermediate phase in ZnSb films by NiO-doping

Wang

et al. 2017

Sci Rep

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The structural evolution and phase-change kinetics of NiO-doped ZnSb films are investigated. NiO-doped ZnSb films exhibit a single-step crystallization process, which is different from that of undoped ZnSb. NiO-doped ZnSb can directly crystallize into a stable ZnSb phase at temperatures greater than 320 °C with suppression of a metastable ZnSb phase. These characteristics enlarge the amorphous/crystalline resistance ratio by approximately five orders of magnitude. Moreover, NiO doping of ZnSb films increases crystallization temperature from 260 to 275 °C, improves data retention temperature from 201.7 to 217.3 °C and increases crystalline activation energy from 5.64 to 6.34 eV. The improvement of the thermal parameters in the nanocomposite can be attributed to stable ZnSb grain growth refinement owing to the dispersion of NiO particles in the sample matrix. This provides additional nucleation sites and produces more ZnSb/NiO interfaces, which can initiate the nucleation and accelerate crystallization. The kinetic exponent n decreases from 1.12 to 0.44, which confirms the ultrafast one-dimensional growth and heterogeneous phase transition of the NiO-doped ZnSb films. The improved thermal stability, larger resistance ratio and direct transition to a stable phase with ultrafast one-dimensional crystal growth indicate the good potential of these materials in phase-change memory applications.

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“…Contrary to most PCMs, the undoped GaSb exhibits an decrease in mass density leading to an increase in film thickness upon crystallization. 17,23 The results deduced from XRR are summarized in Table I. At any Ge-doping level, a negative mass density change upon crystallization is observed.…”

Section: Ge Doping Level T X ( C)mentioning

confidence: 99%

“…15 The stoichiometric GaSb alloy shows actually negative optical contrast (higher optical reflectance in the amorphous state) 16 associated with a decrease in mass density upon crystallization. 17 By increasing the Sb content in Ga 1Àx Sb x alloys up to 91 at. % Sb, no change in mass density nor in film thickness was evidenced in the Ga 0.3 Sb 0.7 material.…”

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confidence: 99%

“…% Sb, no change in mass density nor in film thickness was evidenced in the Ga 0.3 Sb 0.7 material. 17 However, increasing Sb ratio in Ga-Sb alloy decreases the crystallization temperature (T x ) and leads to Sb segregation. 15 In this context, the main objective of the present study is to tune Ga-Sb alloy composition for (i) combining zero mass density change upon crystallization with a higher crystallization temperature and (ii) improving both data retention and cyclability for memory applications.…”

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confidence: 99%

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Ge-doped GaSb thin films with zero mass density change upon crystallization for applications in phase change memories

Putero

Coulet

Müller

et al. 2016

Applied Physics Letters

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International audienceIn order to optimize materials for phase change random access memories (PCRAM), the effect of Ge doping on Ga-Sb alloy crystallization was studied using combined in situ synchrotron x-ray techniques, electrical measurements, and static laser testing. The present data emphasize that the crystallization temperature can be increased up to 390 degrees C with subsequent higher thermal stability of the amorphous phase; phase segregation is evidenced with GaSb, Sb, and Ge phases that crystallize in a two-step crystallization process. The Ge-doped GaSb films exhibit a larger electrical contrast as compared to undoped GaSb alloy (up to x 100). The optical contrast measured by laser testing is shown to follow the mass density change variations upon crystallization, with a negative contrast (higher value in amorphous state) whatever Ge-doping levels. In situ x-ray reflectivity measurements show that zero mass density change can be achieved by low Ge-doping. Ge-doped GaSb alloys look promising since a phase change material with zero mass density change and higher crystallization temperature satisfactorily fulfills the specifications for reliable PCRAM cells in terms of endurance and data retention. (C) 2016 AIP Publishing LLC

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Density change upon crystallization of Ga-Sb films

Cited by 20 publications

References 27 publications

A zero density change phase change memory material: GeTe-O structural characteristics upon crystallisation

A zero density change phase change memory material: GeTe-O structural characteristics upon crystallisation

Suppression for an intermediate phase in ZnSb films by NiO-doping

Ge-doped GaSb thin films with zero mass density change upon crystallization for applications in phase change memories

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