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.

Laser Synthesis of Sn-Ge-Sb-Te Phase Change Materials

2006 ◽  
Vol 918 ◽  
Author(s):  
Wendong Song ◽  
L.P. Shi ◽  
X.S. Miao ◽  
T.C. Chong
Keyword(s):  
Thin Films ◽  
Phase Change ◽  
Crystallization Temperature ◽  
Photoelectron Spectroscopy ◽  
Phase Change Materials ◽  
Frequency Factor ◽  
Ramp Rate ◽  
Laser Synthesis ◽  
Si Substrates ◽  
Change Temperature

AbstractSn-doped Ge-Sb-Te films on Si substrates were prepared by laser synthesis at the different growth temperatures. The compositions of Sn-doped Ge-Sb-Te films were analysized by X-ray photoelectron spectroscopy. The crystal structures of Sn-doped Ge-Sb-Te thin films with a Sn content of less than 30 at% are close to Ge2Sb2Te5. The crystallization behaviors of Sn-doped Ge-Sb-Te films were analyzed by self-developed phase change temperature tester. The crystallization temperatures of Sn4.3Ge32.9Sb28.1Te34.6, Sn9.8Ge20.3Sb28.4Te41.5 and Sn18.8Ge19.5Sb25.3Te36.4 are 141.5, 137.3 and 135.0 °C at a ramp rate of 20 °C/min, respectively. Doping Sn into Ge-Sb-Te will result in a decrease of crystallization temperature. It was also found that crystallization temperature increases with an increase of ramp rate for a phase change material. The activity energy Ea and frequency factor ¦Ô for Sn9.8Ge20.3Sb28.4Te41.5 thin films are 2.42 eV and 1.7 × 1026 Hz, respectively. The crystallization speed of Sn-doped Ge-Sb-Te is estimated to be faster than Ge2Sb2Te5.

scholarly journals Density-functional theory guided advances in phase-change materials and memories

MRS Bulletin ◽  
2015 ◽  
Vol 40 (10) ◽  
pp. 856-869 ◽  
Author(s):  
Wei Zhang ◽  
Volker L. Deringer ◽  
Richard Dronskowski ◽  
Riccardo Mazzarello ◽  
Evan Ma ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Phase Change ◽  
Density Functional ◽  
Phase Change Materials ◽  
Functional Theory ◽  
Image Position

Abstract

scholarly journals Characterization of MgCl2·6H2O-Based Eutectic/Expanded Perlite Composite Phase Change Material with Low Thermal Conductivity

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2369 ◽  
Author(s):  
Chao Zhang ◽  
Zeyu Zhang ◽  
Rongda Ye ◽  
Xuenong Gao ◽  
Ziye Ling
Keyword(s):  
Thermal Conductivity ◽  
Phase Separation ◽  
Phase Change ◽  
Phase Change Materials ◽  
Impregnation Method ◽  
Expanded Perlite ◽  
Thermal Reliability ◽  
Low Thermal Conductivity ◽  
Human Thermal Comfort ◽  
Save Energy

The melting points of the phase change materials (PCMs) incorporated into the walls of buildings should be within the human thermal comfort temperature range. In this paper, 15 wt.% of MgCl2·6H2O was mixed with CaCl2·6H2O to obtain the eutectic with a melting point of 23.9 °C. SrCl2·6H2O suppresses the supecooling of the eutectic. The combination with expanded perlite (EP) via the impregnation method overcomes the phase separation and liquid leakage of the CaCl2∙6H2O-MgCl2∙6H2O mixture. The composite PCM is form-stable with the maximum loading mass fraction up to 50 wt.% and latent heat of 73.55 J/g. EP also significantly reduces the thermal conductivity of the CaCl2∙6H2O-MgCl2∙6H2O from 0.732 to 0.144 W/(m·K). The heating-cooling cycling test reveals that the composite PCM is thermally stable. The cheap eutectic salt hydrate, with little supercooling, no phase separation and liquid leakage, low thermal conductivity and good thermal reliability, show great potential as envelope materials to save energy consumption in buildings.

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.

Properties of Phase Change Materials Modified by Ion Implantation

2011 ◽  
Vol 1338 ◽  
Author(s):  
Simone Raoux ◽  
Guy M. Cohen ◽  
Marinus Hopstaken ◽  
Siegfried Maurer ◽  
Jean L. Jordan Sweet
Keyword(s):  
Ion Implantation ◽  
Phase Change ◽  
Crystallization Temperature ◽  
Phase Change Materials ◽  
High Dose ◽  
Carbon Ions ◽  
X Ray Diffraction ◽  
Additional Tool ◽  
20 Nm ◽  
Ion Species

ABSTRACTIon implantation of germanium and carbon ions into thin films of Ge2Sb2Te5 (GST) and GeTe was applied to modify the properties of these phase change materials. It was found that it is possible to amorphize crystalline GST and GeTe using ion implantation for optimized ion doses and energies which depend on the film thickness, ion species and capping layer. A relatively low minimum dose is required for complete amorphization as judged by the absence of diffraction peaks in x-ray diffraction (XRD) scans. It is 4–5×1013 cm−2 for germanium implantation into GST, and slightly higher (1014 cm−2) for germanium implantation into GeTe. The properties of the re-amorphized films depend on ion species, dose and energy. The re-crystallization temperature of re-amorphized GST by ion implantation is comparable or higher than as-deposited amorphous GST. Carbon implantation in particular leads to a large increase in the crystallization temperature Tx. A carbon dose of 1016 cm−2 implanted into 20 nm amorphous GST yielded a crystallization temperature of 300 ºC, much higher than the crystallization temperature of 160 ºC we recorded for as-deposited, amorphous GST. Similarly, high dose carbon implantation into amorphous GeTe leads to large increase in Tx. We recorded a shift in Tx from 195 ºC for as-deposited GeTe to 400 ºC for C-implanted GeTe. Crystalline GeTe re-amorphized by a low dose germanium ion implantation exhibits a re-crystallization temperature below Tx of as-deposited amorphous GeTe and Tx increased with the implanted Ge dose to a crystallization temperature above that of unimplanted GeTe. Ion implantation can be regarded an additional tool to create phase change materials with different and improved switching properties that cannot be achieved by conventional sputter deposition.

scholarly journals High-throughput experiment for the rapid screening of organic phase change materials

2021 ◽  
Author(s):  
Clément Mailhé ◽  
Stéphane Gorsse ◽  
Boèce Thirion ◽  
Elena Palomo ◽  
Marie Duquesne
Keyword(s):  
Phase Change ◽  
Organic Phase ◽  
High Throughput ◽  
Phase Change Materials ◽  
Rapid Screening

scholarly journals Microfluidic Preparation of Janus Microparticles With Temperature and pH Triggered Degradation Properties

2021 ◽  
Vol 9 ◽  
Author(s):  
Zi-Yi Feng ◽  
Tao-Tao Liu ◽  
Zhen-Tao Sang ◽  
Zhen-Sheng Lin ◽  
Xin Su ◽  
...  
Keyword(s):  
Phase Separation ◽  
Drug Release ◽  
Phase Change ◽  
Phase Change Materials ◽  
Janus Particles ◽  
Experimental Conditions ◽  
Application Range ◽  
Physiological Temperature ◽  
Microfluidic Flow ◽  
Degradation Properties

Based on the phase separation phenomenon in micro-droplets, polymer-lipid Janus particles were prepared on a microfluidic flow focusing chip. Phase separation of droplets was caused by solvent volatilization and Janus morphology was formed under the action of interfacial tension. Because phase change from solid to liquid of the lipid hemisphere could be triggered by physiological temperature, the lipid hemisphere could be used for rapid release of drugs. While the polymer we selected was pH sensitive that the polymer hemisphere could degrade under acidic conditions, making it possible to release drugs in a specific pH environment, such as tumor tissues. Janus particles with different structures were obtained by changing the experimental conditions. To widen the application range of the particles, fatty alcohol and fatty acid-based phase change materials were also employed to prepare the particles, such as 1-tetradecanol, 1-hexadecanol and lauric acid. The melting points of these substances are higher than the physiological temperature, which can be applied in fever triggered drug release or in thermotherapy. The introduction of poly (lactic-co-glycolic acid) enabled the formation of multicompartment particles with three distinct materials. With different degradation properties of each compartment, the particles generated in this work may find applications in programmed and sequential drug release triggered by multiple stimuli.

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