• Title, Summary, Keyword: Phase-change

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Synthesis and Analysis of Ge2Sb2Te5 Nanowire Phase Change Memory Devices

  • Lee, Jun-Yeong;Kim, Jeong-Hyeon;Jeon, Deok-Jin;Han, Jae-Hyeon;Yeo, Jong-Seok
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.222.2-222.2
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    • 2015
  • A $Ge_2Sb_2Te_5$ nanowire (GST NW) phase change memory device is investigated with Joule heating electrodes. GST is the most promising phase change materials, thus has been studied for decades but atomic structure transition in the phase-change area of single crystalline phase-change material has not been clearly investigated. We fabricated a phase change memory (PCM) device consisting of GST NWs connected with WN electrodes. The GST NW has switching performance with the reset/set resistance ratio above $10^3$. We directly observed the changes in atomic structure between the ordered hexagonal close packed (HCP) structure and disordered amorphous phase of a reset-stop GST NW with cross-sectional STEM analysis. Amorphous areas are detected at the center of NW and side areas adjacent to heating electrodes. Direct imaging of phase change area verified the atomic structure transition from the migration and disordering of Ge and Sb atoms. Even with the repeated phase transitions, periodic arrangement of Te atoms is not significantly changed, thus acting as a template for recrystallization. This result provides a novel understanding on the phase-change mechanism in single crystalline phase-change materials.

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A Study on Quantitative Performance Index for Phase-Change Cooling Systems (상변화 냉각시스템의 정량적 성능지수 연구)

  • Jang, Myeong-Eon;Song, Hye-Eun
    • Journal of the Korea Institute of Military Science and Technology
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    • v.23 no.3
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    • pp.237-245
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    • 2020
  • In this paper, I introduce Phase-Change Cooling for thermal management of high power devices that can be applied to High Power Laser and Electric Propulsion Systems which are composed of multiple distributed superheat sources. Phase-Change Cooling can be good used to efficient cooling of their heat sources. Phase-Change Cooling has extremely high efficiency of two-phase heat transport by utilizing heat of vaporization, relatively low flow rates and reduced pumps power. And I suggest TPI(Thermal Performance Index) which is a quantitative performance index of Phase-Change Cooling for thermal management. I quantify the performance of Phase-Change Cooling by introducing TPI. I present the test results of TPI's changing refrigerant, heat sink and flow rate of the Phase-Change Cooling system through the experiments and analyze these results.

Scaling Down Characteristics of Vertical Channel Phase Change Random Access Memory (VPCRAM)

  • Park, Chun Woong;Park, Chongdae;Choi, Woo Young;Seo, Dongsun;Jeong, Cherlhyun;Cho, Il Hwan
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.14 no.1
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    • pp.48-52
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    • 2014
  • In this paper, scaling down characteristics of vertical channel phase random access memory are investigated with device simulator and finite element analysis simulator. Electrical properties of select transistor are obtained by device simulator and those of phase change material are obtained by finite element analysis simulator. From the fusion of both data, scaling properties of vertical channel phase change random access memory (VPCRAM) are considered with ITRS roadmap. Simulation of set reset current are carried out to analyze the feasibility of scaling down and compared with values in ITRS roadmap. Simulation results show that width and length ratio of the phase change material (PCM) is key parameter of scaling down in VPCRAM. Thermal simulation results provide the design guideline of VPCRAM. Optimization of phase change material in VPCRAM can be achieved by oxide sidewall process optimization.

An Analysis of 'The Phase Changes of the Moon', the Contents in Science Textbook of the 9th Grade

  • Chae, Dong-Hyun
    • 한국지구과학회:학술대회논문집
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    • pp.73-73
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    • 2010
  • The purpose of this study is to analyze illustrations, contents, and experiment in 6 kinds of science textbook from the 9th grade covering the phase change of the Moon (on the phase change of the Moon in six 9th grade science textbook) and to suggest coherent and effective contents and frame of the science textbook. Hence, the researcher decided the study problem. The study problems are as follows; 'Are the illustrations in the science textbook presented to help understand the phase change of the Moon depending on the position of the observer?', 'Does the contents of the book clearly mention the phase change of the Moon?', 'Can students understand the phase change of the Moon through the experiments in the science textbook?', 'Do illustrations, contents, and experiment of the science textbook consistently explain phase change of the Moon?'. 10 persons (9graduate students including the researcher) took part in this study. All things unanimously agreed upon by all participants were reflected in the results. The results are as follows. First, the universe observer's view point is mixed with the earth observer's view in illustration of these science textbook regarding the phase change of the Moon. Moreover, illustrations of some textbooks are presented with such words as 'sunrise', 'midnight' and consequently contain too much contents. Second, the contents of the science textbook concerning the phase change of the Moon is not described clearly. In addition, they don't give clear and detailed explanations for the reason of the phase change of the Moon. Third, all of the textbooks, except one textbook, describe the experiment regarding the phase change of the Moon with the earth observer's view point but don't specifically mention that the view point is that of the earth observer's view point. Fourth, illustrations, contents, and experiments in the science textbook don't coherently explain the phase change of the Moon. In addition, it is confirmed through the process of the result analysis that the described contents in the science curriculum is not well constructed or logical.

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The study about phase phase change material at nano-scale using c-AFM method (c-AFM 기술을 이용한 나노급 상변화 소자 특성 평가에 대한 연구)

  • Hong, Sung-Hoon;Lee, Heon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.57-57
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    • 2010
  • In this study, nano-sized phase change materials were evaluated using nanoimprint lithography and c-AFM technique. The 200nm in diameter phase change nano-pillar device of GeSbTe, AgInSbTe, InSe, GeTe, GeSb were successfully fabricated using nanoimprint lithography. And the electrical properties of the phase change nano-pillar device were evaluated using c-AFM with pulse generator and voltage source.

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Electrical and thermal characteristics of PRAM with thickness of phase change thin film (상변화 박막의 두께에 따른 상변화 메모리의 전류 및 열 특성)

  • Choi, Hong-Kyw;Kim, Hong-Seung;Lee, Seong-Hwan;Jang, Nak-Won
    • Journal of Advanced Marine Engineering and Technology
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    • v.32 no.1
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    • pp.162-168
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    • 2008
  • In this paper, we analyzed the heat transfer phenomenon and the reset current variation of PRAM device with thickness of phase change material using the 3-D finite element analysis tool. From the simulation, Joule's heat was generated at the contact surface of phase change material and bottom electrode of PRAM. As the thickness of phase change material was decreased, the reset current was highly increased. In case thickness of phase change material thin film was $200\;{\AA}$, heat increased through top electrode and reset current caused by phase transition highly increased. And as thermal conductivity of top electrode decreased, temperature of unit memory cell was increased.

The Effects of Additives on the Cooling Characteristic of a Clathrate Compound (포접화합물의 냉각특성에 대한 첨가제의 영향)

  • Kim Jin Heung;Chung Nak Kyu;Kim Suk Hyun;Kim Chang Oh
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.2
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    • pp.125-130
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    • 2005
  • This study was peformed to investigate the phase change temperature, the supercooling, the maintenance time of liquid phase and the change rate of volume of TMA 30 $wt\% clathrate compound with additives. TMA 30 $wt\% clathrate compound with additive was cooled at heat source temperature of $-6^{circ}C$. The additives are ethylene glycol and chloroform. Their concentration are 0.1$wt\% respectively. The experimental results showed that the phase change temperature was not affected by additives and this was average $5.3^{circ}C$. Also the supercooling and the maintenance time of liquid phase were decreased by additives. Especially, the average value of supercooling showed by $8.8^{circ}C$ and the maintenance time of liquid phase was by 19 minutes in the case of chloroform 0.1$wt\%. Additionally, the average change rate of volume showed by $1.26{\~}1.31\%$ according to additives and the volume was decreased by the phase change from liquid to solid.

Analysis of Phase Change Materials for Production of Changable Mold for Free-form Concrete Segment (FCS 가변형 몰드 생산을 위한 PCM 분석)

  • Lee, Donghoon;Kim, Sunkuk
    • Proceedings of the Korean Institute of Building Construction Conference
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    • pp.150-151
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    • 2014
  • A mold of free-form concrete segment can be used only one time. Thus, the construction duration and cost are increased. The materials of the mold such as wood and metal have limitations due to the implementation and reuse. The review of the material of the mold for free-form concrete segment is needed to reduce duration and production cost. Phase change material can be used both to implement free-shape by heating and to produce mold after cooling. After using Phase change material can be re-used to mold by heating. The scope of this study is many kind of phase change materials for molding. The aim of this study is to analyze the phase change materials for production of changable mold for free-form concrete segment. In this study, the paraffin wax that is melted at 64℃ was selected by considering both the energy efficiency and the weather of Korea.

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Experimental Study on Accelerating Phase Change Heat Transfer (상변화 물질의 상변이 촉진에 관한 실험적 연구)

  • 박설현;오율권;차경옥
    • Journal of Advanced Marine Engineering and Technology
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    • v.26 no.1
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    • pp.23-29
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    • 2002
  • Solid-liquid phase change (i.e. melting or solidification) occurs in a number of situations of practical interest. Some common examples include the melting of edible oil, metallurgical process such as casting and welding, and materials science applications such as crystal growth. Therefore, due to the practical importance of the subject, there have been a large number of experimental and numerical studies of problems involving phase change during the past few decades. Also, this study presented the effective way to enhance phase change heat transfer.

A Study on Thermo-Physical Properties of Microencapsulated Phase Change Material Slurry (마이크로캡슐 잠열 축열재 혼합수의 열물성에 관한 연구)

  • 임재근;최순열;김명준
    • Journal of Advanced Marine Engineering and Technology
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    • v.28 no.6
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    • pp.962-971
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    • 2004
  • This paper has dealt with thermo-physical properties of microencapsulated phase change material slurry as a latent heat storage material having a low melting point. The measured results of the thermo-physical properties of the test microencapsulated phase change material slurry, those are, density, specific heat, thermal conductivity and viscosity, were discussed for the temperature region of solid and liquid phases of the dispersion material (paraffin). The measurements of these properties of microencapsulated phase change material slurry have been carried out by using a specific-gravity meter, a water calorimeter, a differential scanning calorimeter(DSC), a transient hot wire method and rotating type viscometer, respectively. It was clarified that the additional properties law could be applied to the estimation of the density and specific heat of microencapsulated phase change material slurry and also the Euckens equation could be applied to the estimation of the thermal conductivity of this slurry.