• Title/Summary/Keyword: phase change materials

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Optical Transmission Characteristics of Tellurium-based Phase-change Chalcogenide Thin Films (Tellurium계 상변화 칼코겐화물 박막의 광투과 특성)

  • Yoon, Hoi Jin;Bang, Ki Su;Lee, Seung-Yun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.29 no.7
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    • pp.408-413
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    • 2016
  • The dielectric thin films applied to multi-colored semitransparent thin film solar cells have been extensively studied. In this work, we prepared GeSbTe and GeTe chalcogenide thin films using magnetron sputtering, and investigated their optical and phase-change properties to replace the dielectric films. The changes of surface morphology, sheet resistance, and X-ray diffraction of the Te-based chalcogenide films support the fact that the amorphous stability of GeTe films is superior to that of GeSbTe films. While both amorphous GeSbTe and GeTe films thinner than 30 nm have optical transparency between 5% and 60%, GeTe films transmit more visible light than GeSbTe films. It is confirmed by computer simulation that the color of semitransparent silicon thin film solar cells can be adjusted with the addition of GeSbTe or GeTe films. Since it is possible to adjust the contrast of the solar cells by exploiting the phase-change property, the two kinds of chalcogenide films are anticipated to be used as an optical layer in semitransparent solar cells.

InSbTe phase change materials deposited in nano scaled structures by metal organic chemical vapor deposition (MOCVD법에 의해 나노급 구조 안에 증착된 InSbTe 상변화 재료)

  • Ahn, Jun-Ku;Park, Kyung-Woo;Cho, Hyun-Jin;Hur, Sung-Gi;Yoon, Soon-Gil
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.52-52
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    • 2009
  • To date, chalcogenide alloy such as $Ge_2Sb_2Te_5$(GST) have not only been rigorously studied for use in Phase Change Random Access Memory(PRAM) applications, but also temperature gap to make different states is not enough to apply to device between amorphous and crystalline state. In this study, we have investigated a new system of phase change media based on the In-Sb-Te(IST) ternary alloys for PRAM. IST chalcogenide thin films were prepared in trench structure (aspect ratio 5:1 of length=500nm, width=100nm) using Tri methyl Indium $(In(CH_3)_4$), $Sb(iPr)_3$ $(Sb(C_3H_7)_3)$ and $Te(iPr)_2(Te(C_3H_7)_2)$ precursors. MOCVD process is very powerful system to deposit in ultra integrated device like 100nm scaled trench structure. And IST materials for PRAM can be grown at low deposition temperature below $200^{\circ}C$ in comparison with GST materials. Although Melting temperature of 1ST materials was $\sim 630^{\circ}C$ like GST, Crystalline temperature of them was ~$290^{\circ}C$; one of GST were $130^{\circ}C$. In-Sb-Te materials will be good candidate materials for PRAM applications. And MOCVD system is powerful for applying ultra scale integration cell.

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Electrical characteristic of differential ternary chalcogenide thin films (칼코게나이드 3원계 박막에서의 전기적 특성에 관한 연구)

  • Yang, Sung-Jun;Shin, Kyung;Lee, Jae-Min;Chung, Hong-Bay
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.07a
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    • pp.377-380
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    • 2004
  • The phase transition between amorphous and crystalline states in chalcogenide semiconductor films can controlled by electric pulses or pulsed laser beam; hence some chalcogenide semiconductor films can be applied to electrically write/erase nonvolatile memory devices, where the low conductive amorphous state and the high conductive crystalline state are assigned to binary states. GeSbTe(GST), AsSbTe(AST), SeSbTe(SST) used to phase change materials by appling electrical pulses. Thickness of ternary chalcogenide thin films have about 100nm. Upper and lower electrode were made of Al. It is compared with I-V characteristics after impress the variable pulses.

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Effect of Encapsulation Ratio on the Phase Transition Kinetics of the SiO2 Encapsulated Paraffin Phase Change Materials (SiO2 캡슐화 파라핀 상변화 물질의 상전이 역학에 대한 캡슐화 비율의 영향)

  • Soumen, Mandal;Lee, Han-Seung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2023.05a
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    • pp.99-100
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    • 2023
  • In this study, an approach has been made to understand the effect of encapsulation thickness of the nanoencapsulated PCMs on the phase transition kinetics. Paraffin is encapsulated by silica via single pot polycondensation reaction. Different ratios of silica precursor are chosen to encapsulate paraffin. The obtained encapsulated PCMs are identified as nano sized, as well as with increasing silica precursor, thicker silica encapsulations have been manifested with shrinking core diameter. The synthesized PCMs are characterized using various characterization techniques. Isochronal kinetic studies are done in differential scanning calorimeter (DSC) to understand about their phase transformation behaviors. This study can appreciate the cognition of the large-scale applications of PCMs into the building constructions as well as the fundamental conception on the phase transition kinetics of PCMs can also be amended.

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Formation of Threshold Switching Chalcogenide for Phase Change Switch Applications

  • Bang, Ki Su;Lee, Seung-Yun
    • Applied Science and Convergence Technology
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    • v.23 no.1
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    • pp.34-39
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    • 2014
  • The programmable switches which control the delivery of electrical signals in programmable logic devices are fabricated using memory technology. Although phase change memory (PCM) technology is one of the most promising candidates for the manufacturing of the programmable switches, the threshold switching material should be added to a PCM cell for realization of the programmable switches based on PCM technology. In this work, we report the impurity-doped $Ge_2Sb_2Te_5$ (GST) chalcogenide alloy exhibiting threshold switching property. Unlike the GST thin film, the doped GST thin film prepared by the incorporation of In and P into GST is not crystallized even at the postannealing temperature higher than $200^{\circ}C$. This specific crystallization behavior in the doped GST thin film is attributed to the stabilization of the amorphous phase of GST by In and P doping.

Investigation of Factors for Promoting Densification of the Sintered Compact during Pressurized Sintering of the Amorphous Ti5Si3 MA Powder (비정질상인 Ti5Si3 MA분말의 가압소결 동안 소결체의 치밀화 촉진현상 요인에 대한 조사)

  • Han, Chang-Suk;Jin, Sung-Yooun;Kwon, Hyuk-Ku
    • Korean Journal of Materials Research
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    • v.30 no.6
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    • pp.301-307
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    • 2020
  • In this study, factors considered to be causes of promotion of densification of sintered pellets identified during phase change are reviewed. As a result, conclusions shown below are obtained for each factor. In order for MA powder to soften, a temperature of 1,000 K or higher is required. In order to confirm the temporary increase in density throughout the sintered pellet, the temperature rise due to heat during phase change was found not to have a significant effect. While examining the thermal expansion using the compressed powder, which stopped densification at a temperature below the MA powder itself, and the phase change temperature, no shrinkage phenomenon contributing to the promotion of densification is observed. The two types of powder made of Ti-silicide through heat treatment are densified only in the high temperature region of 1,000 K or more; it can be estimated that this is the effect of fine grain superplasticity. In the densification of the amorphous powder, the dependence of sintering pressure and the rate of temperature increase are shown. It is thought that the specific densification behavior identified during the phase change of the Ti-37.5 mol.%Si composition MA powder reviewed in this study is the result of the acceleration of the powder deformation by the phase change from non-equilibrium phase to equilibrium phase.

Effects of Mo Content on Surface Characteristics of Dental Ni-Ti Alloys (치과용 Ni-Ti합금의 표면특성에 미치는 Mo함량의 영향)

  • Han-Cheol Choe;Jae-Un Kim;Sun-Kyun ark
    • Corrosion Science and Technology
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    • v.22 no.1
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    • pp.64-72
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    • 2023
  • Ni-Ti shape memory alloy for dental nerve treatment devices was prepared by adding Mo to Ni-Ti alloy to improve flexibility and fatigue fracture characteristics and simultaneously increase corrosion resistance. Surface properties of the alloy were evaluated. Microstructure analysis of the Ni-Ti-xMo alloy revealed that the amount of needle-like structure increased with increasing Mo content. The shape of the precipitate showed a pattern in which a long needle-like structure gradually disappeared and changed into a small spherical shape. As a result of XRD analysis of the Ni-Ti-xMo alloy, R-phase structure appeared as Mo was added. R-phase and B2 structure were mainly observed. As a result of DSC analysis, phase transformation of the Ti-Ni-Mo alloy showed a two-step phase change of B2-R-B19' transformation with two exothermic peaks and one endothermic peak. As Mo content increased, R-phase formation temperature gradually decreased. As a result of measuring surface hardness of the Ti-Ni-Mo alloy, change in hardness value due to the phase change tended to decrease with increasing Mo content. As a result of the corrosion test, the corrosion potential and pitting potential increased while the current density tended to decrease with increasing Mo content.

Thin Film Deposition of Antimony Tellurides for Ge-Sb-Te Compounds

  • Han, Byeol;Kim, Yu-Jin;Park, Jae-Min;Mayangsari, Tirta R.;Lee, Won-Jun
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.330.1-330.1
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    • 2014
  • 개인용 노트북, 태블릿 PC, 핸드폰 기술 발전에 의해 언제 어디서나 데이터를 작성하고 기록하는 일들이 가능해졌다. 특히 cloud 시스템을 이용하여 데이터를 휴대기기에 직접 저장하지 않고 server에 기록하는 일들이 가능해짐에 따라 server 기기의 성능, server-room power 및 space 에 대한 관심이 증가하였다. Storage class memory (SCM) 이란 memory device와 storage device의 장점을 결합한 memory를 일컫는 기술로 현재 소형 디바이스 부분부터 점차 그 영역을 넓히고 있다. 그중 phase change material을 이용한 phase change memory (PCM) 기술이 가장 각광받고 있다. PCM의 경우 scaling됨에 의해 cell간의 열 간섭으로 인한 data 손실의 우려가 있어 cell의 면적을 최소화 하여 소자를 제작하여야 한다. 기존의 sputtering등의 PVD 방법으로는 한계가 있어 ALD 공정을 이용한 PCM에 대한 연구가 활발히 진행중이다. 특히 tellurium 원료기체로 silyl 화합물 [1]을 사용하여 주로 $Ge_2Sb_2Te_5$의 조성에 초점을 맞춰 진행되고 있으나, 세부 공정에 대한 기본적인 연구는 미비하다. 본 연구에서는 Ge-Sb-Te 3원계 박막을 형성하기 위한 Sb-Te 화합물의 증착 공정에 대한 연구를 수행하였다. 특히 원료기체로 Si이 없는 새로운 Te 원료기체를 이용하여 조성 조절을 하였고, 박막의 물성을 분석하였다. 또한 공정온도에 따른 박막의 물성 변화를 분석하였다.

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An Experimental Study on melting phenomena of PCM affected by Ultrasonic Vibration in a square cavity (밀폐용기내에서 초음파 진도에 따른 상변화물질의 용융현상 연구)

  • Youn, Joung-Hwan;Joung, Dae-Hun;Oh, Yool-Kwon
    • Proceedings of the KSME Conference
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    • 2001.06d
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    • pp.246-251
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    • 2001
  • 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.

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