scholarly journals Tailoring the Structural and Optical Properties of Germanium Telluride Phase-Change Materials by Indium Incorporation

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 3029
Author(s):  
Xudong Wang ◽  
Xueyang Shen ◽  
Suyang Sun ◽  
Wei Zhang
Keyword(s):  
Thermal Stability ◽  
Optical Properties ◽  
Phase Change ◽  
Phase Change Materials ◽  
Random Access ◽  
Global Memory ◽  
Great Promise ◽  
Germanium Telluride ◽  
Structural Details ◽  
Tie Line

Chalcogenide phase-change materials (PCMs) based random access memory (PCRAM) enter the global memory market as storage-class memory (SCM), holding great promise for future neuro-inspired computing and non-volatile photonic applications. The thermal stability of the amorphous phase of PCMs is a demanding property requiring further improvement. In this work, we focus on indium, an alloying ingredient extensively exploited in PCMs. Starting from the prototype GeTe alloy, we incorporated indium to form three typical compositions along the InTe-GeTe tie line: InGe3Te4, InGeTe2 and In3GeTe4. The evolution of structural details, and the optical properties of the three In-Ge-Te alloys in amorphous and crystalline form, was thoroughly analyzed via ab initio calculations. This study proposes a chemical composition possessing both improved thermal stability and sizable optical contrast for PCM-based non-volatile photonic applications.

scholarly journals Metal - Insulator Transition Driven by Vacancy Ordering in GeSbTe Phase Change Materials

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Valeria Bragaglia ◽  
Fabrizio Arciprete ◽  
Wei Zhang ◽  
Antonio Massimiliano Mio ◽  
Eugenio Zallo ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Random Access ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Reversible Transformation ◽  
Vacancy Ordering

Abstract Phase Change Materials (PCMs) are unique compounds employed in non-volatile random access memory thanks to the rapid and reversible transformation between the amorphous and crystalline state that display large differences in electrical and optical properties. In addition to the amorphous-to-crystalline transition, experimental results on polycrystalline GeSbTe alloys (GST) films evidenced a Metal-Insulator Transition (MIT) attributed to disorder in the crystalline phase. Here we report on a fundamental advance in the fabrication of GST with out-of-plane stacking of ordered vacancy layers by means of three distinct methods: Molecular Beam Epitaxy, thermal annealing and application of femtosecond laser pulses. We assess the degree of vacancy ordering and explicitly correlate it with the MIT. We further tune the ordering in a controlled fashion attaining a large range of resistivity. Employing ordered GST might allow the realization of cells with larger programming windows.

scholarly journals High-Throughput Calculations on the Decomposition Reactions of Off-Stoichiometry GeSbTe Alloys for Embedded Memories

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2382
Author(s):  
Omar Abou El Kheir ◽  
Marco Bernasconi
Keyword(s):  
Phase Separation ◽  
Phase Change ◽  
High Throughput ◽  
Crystallization Temperature ◽  
Density Functional ◽  
Phase Change Materials ◽  
Ternary Phase Diagram ◽  
Decomposition Reactions ◽  
Embedded Memories ◽  
Tie Line

Chalcogenide GeSbTe (GST) alloys are exploited as phase change materials in a variety of applications ranging from electronic non-volatile memories to neuromorphic and photonic devices. In most applications, the prototypical Ge2Sb2Te5 compound along the GeTe-Sb2Te3 pseudobinary line is used. Ge-rich GST alloys, off the pseudobinary tie-line with a crystallization temperature higher than that of Ge2Sb2Te5, are currently explored for embedded phase-change memories of interest for automotive applications. During crystallization, Ge-rich GST alloys undergo a phase separation into pure Ge and less Ge-rich alloys. The detailed mechanisms underlying this transformation are, however, largely unknown. In this work, we performed high-throughput calculations based on Density Functional Theory (DFT) to uncover the most favorable decomposition pathways of Ge-rich GST alloys. The knowledge of the DFT formation energy of all GST alloys in the central part of the Ge-Sb-Te ternary phase diagram allowed us to identify the cubic crystalline phases that are more likely to form during the crystallization of a generic GST alloy. This scheme is exemplified by drawing a decomposition map for alloys on the Ge-Ge1Sb2Te4 tie-line. A map of decomposition propensity is also constructed, which suggests a possible strategy to minimize phase separation by still keeping a high crystallization temperature.

Yttrium-doped Sb2Te as high speed phase-change materials with good thermal stability

2019 ◽  
Vol 247 ◽  
pp. 60-62 ◽  
Author(s):  
Tao Li ◽  
Liangcai Wu ◽  
Yong Wang ◽  
Guangyu Liu ◽  
Tianqi Guo ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Phase Change ◽  
High Speed ◽  
Phase Change Materials ◽  
Good Thermal Stability

scholarly journals Edible Oils as Practical Phase Change Materials for Thermal Energy Storage

2019 ◽  
Vol 9 (8) ◽  
pp. 1627 ◽  
Author(s):  
Samer Kahwaji ◽  
Mary Anne White
Keyword(s):  
Thermal Stability ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Edible Oils ◽  
Coconut Oil ◽  
Heat Of Fusion ◽  
Vegetable Shortening

Edible oils could provide more accessible alternatives to other phase change materials (PCMs) for consumers who wish to build a thermal energy storage (TES) system with sustainable materials. Edible oils have good shelf life, can be acquired easily from local stores and can be less expensive than other PCMs. In this work, we explore whether margarine, vegetable shortening, and coconut oil are feasible PCMs, by investigations of their thermal properties and thermal stability. We found that margarine and vegetable shortening are not useful for TES due to their low latent heat of fusion, ΔfusH, and poor thermal stability. In contrast, coconut oil remained thermally stable after 200 melt-freeze cycles, and has a large ΔfusH of 105 ± 11 J g−1, a low degree of supercooling and a transition temperature, Tmpt = 24.5 ± 1.5 °C, that makes it very useful for TES in buildings. We also determined coconut oil’s heat capacity and thermal conductivity as functions of temperature and used the measured properties to evaluate the feasibility of coconut oil for thermal buffering and passive heating of a residential-scale greenhouse.

Thermal stability of renewable diesters as phase change materials

2016 ◽  
Vol 644 ◽  
pp. 61-68 ◽  
Author(s):  
Latchmi Raghunanan ◽  
Michael C. Floros ◽  
Suresh S. Narine
Keyword(s):  
Thermal Stability ◽  
Phase Change ◽  
Phase Change Materials ◽  
Thermal Stability Of
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