• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.305-306
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• 2008

본 논문에서는 PRAM 에서 기록매질로 이용될 수 있는 최적의 물질을 찾고자 $Ge_2Sb_2Te_5$ 박막에 Al을 첨가하여 비정질-결정질 천이시의 원자구조와 상변화 특성간의 관계를 연구하였다. 이 실험에 사용된 $Al_x(Ge_2Sb_2Te_5)_{1-x}$ 조성은 5N의 금속 파우더를 용융-냉각법으로 벌크를 제작하였고 열증착 방법으로 Si (100) 및 유리 (corning glass, 7059) 기판위에 200nm 두께로 박막을 증착하였다. 비정질 박막의 상변화에 따른 반사도 차이를 평가하기 위해서 658 nm의 LD가 장착된 나노펄스 스캐너를 이용하여 power; 1~17mW, pulse duration; 10~460 ns의 범위에서 각 조성의 비정질-결정질 상변화속도를 측정, 비교 분석하였다. 또한 각각의 박막을 $100^{\circ}C$ 에서 $400^{\circ}C$ 까지 $50^{\circ}C$ 간격으로 $N_2$ 분위기에서 1시간동안 열처리 한 후 XRD와 UV-Vis-NIR spectrophotometer를 사용하여 각 상의 구조분석 및 광학적 특성을 분석하였다. 또한 4-point probe로 면저항을 측정하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.334-345
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• 2008

컴퓨터의 발달과 더불어 현대사회는 기록하고 보존해야할 정보의 양이 점점 방대해 지고 있다. 그로 인해 자기기록매체처럼 정보를 사용자의 편의에 따라 반복적으로 기록하고 재생할 수 있는 광기록매체에 대한 관심이 증가되고 있다. $Ge_2Sb_2Te_5$(GST)는 기존의 CD-RW나 Floppy Disk(FD)를 대체할 차세대 기록매체로 주목받고 있다. 따라서 본 연구에서는 비정질상과 결정상으로 변하는 성질을 가지고 있는 GST롤 상변화 기록매체로서 이용하기 위해 굴절률을 평가하였다. 시료는 5N의 순도를 갖는 Ge, Sb, Te 물질을 준비하고 조성비에 맞추어서 석영관에 진공 봉입한 후 용융-냉각법으로 벌크를 제작하였고 열증착 방법으로 Si 및 유리 기판위에 1000nm 두께로 박막을 제작하였다. UV-Vis-IR spectrophotometer를 사용하여 반사도와 투과도를 측정하였고 측정한 스펙트럼을 이용하여 Swanepoel method로 굴절률을 계산하였다. 본 연구진이 자체 개발한 계산툴에 실험값을 대입하였고 실험에 의해 얻은 투과도와 계산툴에 의해 얻은 투과도 스펙트럼을 비교하였다.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1274-1276
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• 1997

We have investigated the crystallization properties of $Te_x(Sb_{85}Ge_{15})_{100-x}$ (x=0.3, 0.5, 1.0 at.%) thin films as observing the reflectance change, XRD and SEM. The reflectance difference(${\Delta}R$) between amorphous and crystalline phases appears appoximately 20%, in all films, at 780nm(diode laser wavelength). In the case of $Te_{0.5}(Sb_{85}Ge_{15})_{99.5}$ thin film, especially, ${\Delta}R$ is about 30%. Also, amophous-to-crystalline phase change is observed at all films. Therefore, $Te_{0.5}(Sb_{85}Ge_{15})_{99.5}$ thin film can be evaluated as attractive optical recording material with low loss and high contrast ratio.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.6
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• pp.448-453
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• 2019

This work reports the electrical characteristics of and temperature distribution in chalcogenide phase change memory (PCM) devices that have a self-aligned structure. GST (Ge-Sb-Te) chalcogenide alloy films were formed in a self-aligned manner by interdiffusion between sputter-deposited Ge and $Sb_2Te_3$ films during thermal annealing. A transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS) analysis demonstrated that the local composition of the GST alloy differed significantly and that a $Ge_2Sb_2Te_5$ intermediate layer was formed near the $Ge/Sb_2Te_3$ interface. The programming current and threshold switching voltage of the PCM device were much smaller than those of a control device; this implies that a phase transition occurred only in the $Ge_2Sb_2Te_5$ intermediate layer and not in the entire thickness of the GST alloy. It was confirmed by computer simulation, that the localized phase transition and heat loss suppression of the GST alloy promoted a temperature rise in the PCM device.

• Korean Journal of Optics and Photonics
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• v.12 no.5
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• pp.394-400
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• 2001

We studied thermal diffusion properties diffusion properties of multi-layered Ge-Sb-Te alloy thin films for optical recording media by solving the thermal equation. Based on the numerical analysis of optical energy distribution and absorption inside multi-layered films including temperature gradient and heat transfer simultaneously, we proposed the optimum parameters of the input laser power and the multi-layer structure as follow. i) Input laser power is 18 mW, ii) laser exposure time is 60 ns, iii) the thicknesses of the lower and the upper ZnS-SiO$_2$are 140 nm and 20~30 nm respectively, and iv) thickness of Ge-Sb-Te recording film is 20 nm.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.192.2-192
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• 2003

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.231.2-231
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• 2003

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1426-1427
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• 2006

Chalcogenide based phase-change memory has a high capability and potential for the next generation nonvolatile memory device. Fast writing speed, low writing voltage, high sensing margin, low power consume and long cycle of read/write repeatability are also good advantages of nonvolatile phase-change memory. We have been investigated the new material for the phase-change memory. Its composition is consists of chalcogenide $Ge_{1}Se_{1}Te_2$ material. We made this new material to solve problems of conventional phase-change memory which has disadvantage of high power consume and high writing voltage. In the present work, we are manufactured $Ge_{1}Se_{1}Te_{2}/Ge_{2}Sb_{2}Te_{5}/Ge_{1}Se_{1}Te_{2}$ and $Ge_{2}Sb_{2}Te_{5}/Ge_{1}Se_{1}Te_{2}/Ge_{2}Sb_{2}Te_{5}$ sandwich triple layer structure devices are manufactured to investigate its electrical properties. Through the present work, we are willing to ensure a potential of substitutional method to overcome a crystallization problem on PRAM device.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.78-79
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• 2003

타원법(ellipsometry)을 사용하여 광기록 매체용 Ge$_2$Sb$_2$Te／sub 5／(GST) 박막의 성장과정에 따른 타원상수 Ψ와 $\Delta$를 측정하여, GST 박막의 최적성장조건을 연구하였다. 아르곤기체압력과 DC 출력 그리고 기판의 온도를 변화시키면서 GST 박막을 성장시켰다. 제작된 시료들의 분광타원 데이터를 모델링분석하여 GST 박막의 밀도분포를 구하고 한편으로는 GST 박막이 성장하는 동안 측정한 in situ 타원 성장곡선을 분석하여 박막의 밀도분포의 변화를 추적하였다. (중략)

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.4
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• pp.314-320
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• 1998

In this study, we have investigated crystallization properties of $Te_x(Sb_{85}Ge_{15})_{100-x}$ (x=0.3, 0.5, 1.0) thin films prepared by thermal evaporation. The change of reflectance according to phase change from amorphous to crystalline phases with annealing and exposure of diode laser is measured b the n&k analyzer and the surface morphology between amorphous and crystalline phase is analyzed by SEM and AFM. The difference in reflectance($\DeltaR$) between amorphous and crystalline phase appears approximately 20% at the diode laser wavelength, 780nm in all prepared films. Especially, the reflectance difference,$\DeltaR$ comes up to about 30% in $Te_{0.5}(Sb_{85}Ge_{15})_{99.5}$ thin film. Also, amorphous-to-crystalline phase change is observed in all prepared films. As a result of the measurement of the reflectance using diode laser, the reflectance is increased in proportion to the laser power and exposure time in all films. As a result of observing each film with the SEM and AFM, the surface morphology of the annealed and the exposed films are evidently increased than those of as-deposited films. The fast crystallization is occurred by increasing in Te content. Therefore, we conclude that the $Te_{0.5}(Sb_{85}Ge_{15})_{99.5}$ and $Te_1(Sb_{85}Ge_{15})_{99}$ thin films can be evaluated as an attractive optical recording medium with high contast ratio and fast erasing time due to crystallization.