Phase transitions of Ge12Sb88 thin films on high- and low-thermal-conductivity substrates and their potential applications in storage

2021 ◽  
Author(s):  
Xiao-Fang Wang ◽  
Pao-An Lin ◽  
Xue-miao Wen ◽  
Bing-Yuh Lu ◽  
Tian-Le Li ◽  
...  
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Thermal Conductivity ◽  
Phase Change ◽  
Data Storage ◽  
Low Thermal Conductivity ◽  
Storage Devices ◽  
Change Behavior ◽  
Potential Applications ◽  
Initial Resistance

Abstract This study examined the phase-change Ge12Sb88 films that are fabricated through radio-frequency reactive magnetron sputtering to substrates with varying thermal conductivity. The in situ resistance was measured, and X-ray diffraction was conducted to investigate the phase-change behavior of the films under adjustments to the heating and annealing temperature. Differences in the films’ band gaps were determined by a spectrometer. The results were as follows: (1) The initial resistance levels of the films on low-thermal-conductivity substrates were higher than those on high-thermal-conductivity substrates. Resistance ratios were in the range of 102 to 103. The substantial changes in resistance influenced the characteristics of accelerating switching time and reduced the power consumption of the investigated materials. (2) Because of the partial crystallization of the films, an additional phase transition (from FCC1 to FCC2) was observed among thin films on low-thermal-conductivity substrates. This phase transition can be leveraged in the development of data storage devices.

Phase Transition Behaviors and Thermal Conductivity of Ge Doped Sb2Te Thin Films for Phase Change Random Access Memory

2013 ◽  
Vol 367 ◽  
pp. 26-31
Author(s):  
Su Yuan Bai ◽  
Zhe Nan Tang ◽  
Zheng Xing Huang ◽  
Yi Feng Gu
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Thermal Conductivity ◽  
Phase Change ◽  
Composite Films ◽  
Random Access ◽  
Random Access Memory ◽  
Data Retention ◽  
Access Memory ◽  
Ge Doping

The Ge doped Sb2Te thin films (Ge2Sb2Te5, Ge0.15Sb2Te and Ge0.61Sb2Te) were deposited by magnetron co-sputtering using Ge and Sb2Te targets. Ge doping effect on the phase transition behaviors and thermal conductivity of the composite films was investigated. Ge0.61Sb2Te thin films have higher crystallization temperature (~200°C), larger crystallization activation energy (~3.28 eV) , better data retention (~120.8 °Cfor 10 years) and lower thermal conductivity (~0.23 W/mK). Ge0.61Sb2Te thin films is considered to be a promising storage medium for phase change random access memory due to its better thermal stability and lower power consumption.

scholarly journals Introduction of Chalcogenide Glasses to Additive Manufacturing: Nanoparticle Ink Formulation, Inkjet Printing, and Phase Change Devices Fabrication

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. Ahmed Simon ◽  
B. Badamchi ◽  
H. Subbaraman ◽  
Y. Sakaguchi ◽  
L. Jones ◽  
...  
Keyword(s):  
Thin Films ◽  
Phase Change ◽  
Inkjet Printing ◽  
Chalcogenide Glasses ◽  
Dip Coating ◽  
Potential Applications ◽  
Coating Methods ◽  
Report Data ◽  
Nanoparticle Ink ◽  
Ink Formulation

AbstractChalcogenide glasses are one of the most versatile materials that have been widely researched because of their flexible optical, chemical, electronic, and phase change properties. Their application is usually in the form of thin films, which work as active layers in sensors and memory devices. In this work, we investigate the formulation of nanoparticle ink of Ge–Se chalcogenide glasses and its potential applications. The process steps reported in this work describe nanoparticle ink formulation from chalcogenide glasses, its application via inkjet printing and dip-coating methods and sintering to manufacture phase change devices. We report data regarding nanoparticle production by ball milling and ultrasonication along with the essential characteristics of the formed inks, like contact angle and viscosity. The printed chalcogenide glass films were characterized by Raman spectroscopy, X-ray diffraction, energy dispersive spectroscopy and atomic force microscopy. The printed films exhibited similar compositional, structural, electronic and optical properties as the thermally evaporated thin films. The crystallization processes of the printed films are discussed compared to those obtained by vacuum thermal deposition. We demonstrate the formation of printed thin films using nanoparticle inks, low-temperature sintering and proof for the first time, their application in electronic and photonic temperature sensors utilizing their phase change property. This work adds chalcogenide glasses to the list of inkjet printable materials, thus offering an easy way to form arbitrary device structures for optical and electronic applications.

The Hexagonal ↔ Orthorhombic Structural Phase Transition in Claringbullite, Cu4FCl(OH)6

2021 ◽  
Author(s):  
Mark D. Welch ◽  
Jens Najorka ◽  
Michael S. Rumsey ◽  
John Spratt
Keyword(s):  
Phase Transition ◽  
Data Storage ◽  
Structural Phase Transition ◽  
Structural Changes ◽  
Structural Phase ◽  
Magnetic Behavior ◽  
Orthorhombic Phase ◽  
New Mineral ◽  
Storage Devices ◽  
Definition Of

ABSTRACT Frustrated magnetic phases have been a perennial interest to theoreticians wishing to understand the energetics and behavior of quasi-chaotic systems at the quantum level. This behavior also has potentially wide applications to developing quantum data-storage devices. Several minerals are examples of such phases. Since the definition of herbertsmithite, Cu3ZnCl2(OH)6, as a new mineral in 2004 and the rapid realization of the significance of its structure as a frustrated antiferromagnetic phase with a triangular magnetic lattice, there has been intense study of its magnetic properties and those of synthetic compositional variants. In the past five years it has been recognized that the layered copper hydroxyhalides barlowite, Cu4BrF(OH)6, and claringbullite, Cu4FCl(OH)6, are also the parent structures of a family of kagome phases, as they also have triangular magnetic lattices. This paper concerns the structural behavior of claringbullite that is a precursor to the novel frustrated antiferromagnetic states that occur below 30 K in these minerals. The reversible hexagonal (P63/mmc) ↔ orthorhombic (Pnma or Cmcm) structural phase transition in barlowite at 200−270 K has been known for several years, but the details of the structural changes that occur through the transition have been largely unexplored, with the focus instead being on quantifying the low-temperature magnetic behavior of the orthorhombic phase. This paper reports the details of the structural phase transition in natural claringbullite at 100−293 K as studied by single-crystal X-ray diffraction. The transition temperature has been determined to lie between 270 and 293 K. The progressive disordering of Cu at the unusual trigonal prismatic Cu(OH)6 site on heating is quantified through the phase transition for the first time, and a methodology for refining this disorder is presented. Key changes in the behavior of Cu(OH)4Cl2 octahedra in claringbullite have been identified that suggest why the Pnma structure is likely stabilized over an alternative Cmcm structure. It is proposed that the presence of a non-centrosymmetric octahedron in the Pnma structure allows more effective structural relaxation during the phase transition than can be achieved by the Cmcm structure, which has only centrosymmetric octahedra.

Latent Heat Storage: Container Geometry, Enhancement Techniques, and Applications—A Review

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
S. Arunachalam
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Energy ◽  
Heat Exchangers ◽  
Phase Change Materials ◽  
Heat Storage ◽  
Low Thermal Conductivity

Energy storage helps in waste management, environmental protection, saving of fossil fuels, cost effectiveness, and sustainable growth. Phase change material (PCM) is a substance which undergoes simultaneous melting and solidification at certain temperature and pressure and can thereby absorb and release thermal energy. Phase change materials are also called thermal batteries which have the ability to store large amount of heat at fixed temperature. Effective integration of the latent heat thermal energy storage system with solar thermal collectors depends on heat storage materials and heat exchangers. The practical limitation of the latent heat thermal energy system for successful implementation in various applications is mainly from its low thermal conductivity. Low thermal conductivity leads to low heat transfer coefficient, and thereby, the phase change process is prolonged which signifies the requirement of heat transfer enhancement techniques. Typically, for salt hydrates and organic PCMs, the thermal conductivity range varies between 0.4–0.7 W/m K and 0.15–0.3 W/m K which increases the thermal resistance within phase change materials during operation, seriously affecting efficiency and thermal response. This paper reviews the different geometry of commercial heat exchangers that can be used to address the problem of low thermal conductivity, like use of fins, additives with high thermal conductivity materials like metal strips, microencapsulated PCM, composite PCM, porous metals, porous metal foam matrix, carbon nanofibers and nanotubes, etc. Finally, different solar thermal applications and potential PCMs for low-temperature thermal energy storage were also discussed.

scholarly journals Microstructural Study of CMR Films as a Function of Growth Temperature, As-Deposited and Annealed

1995 ◽  
Vol 401 ◽  
Author(s):  
M. E. Hawley ◽  
X. D. Wu ◽  
P. N. Arendt ◽  
C. D. Adams ◽  
M. F. Hundley ◽  
...  
Keyword(s):  
Data Storage ◽  
Growth Temperature ◽  
Magnetic Data ◽  
Storage Devices ◽  
Colossal Magnetoresistive ◽  
Step Flow ◽  
Transmission Electron ◽  
The Family ◽  
Complex Metal Oxides ◽  
Potential Applications

AbstractThe properties encompassed by the family of complex metal oxides span the spectrum from superconductors to insulating ferroelectrics. Included in this family are the new colossal magnetoresistive perovskites with potential applications in advanced high density magnetic data storage devices based on single or multilayer thin films units of these materials fabricated by vapor phase deposition (PVD) methods. The realization of this potential requires solving basic thin film materials problems requiring understanding and controlling the growth of these materials. Toward this end, we have grown La0.7Ca0.3MnO3 and La0.7Sr0.3MnO3 on LaAlO3 single crystal substrates by pulsed laser and RF sputter deposition at temperatures from 500° C to 900° C and annealed at over 900° C for about 10 hours. The evolution of the microstructure of these films was studied by scanning probe microscopies and transmission electron microscopy (TEM).The results of SPM characterization showed that at the lower end of the growth temperature range, the as-grown films were polygranular with grain size increasing with temperature. The 500° C as-grown films appeared to be amorphous while the 750° C film grains were layered with terrace steps often one unit cell high. In contrast, films grown at 900° C consisted of coalesced islands with some 3-D surface crystals. After annealing, all films had coalesced into very large extended layered islands. The change in microstructure was reflected in a decreased resistivity of coalesced films over their unannealed granular precursors. Previous reported work on the growth of La0.84 Sr0.16MnO3 and La0.8Sr0 2CoO3 grown demonstrated the sensitivity of the microstructure to substrate and deposition conditions. Films grown on an “accidental” vicinal surface grew by a step flow mechanism.

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