• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.5-9
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• 1996

As optical massmemories, (Se, S)-based chalcogenide amorphous films are used for a holographic supermicrofiche by using the refractive-index change. In 1000$\AA$thick-As$_{40}$ Ge$_{10}$Se$_{100-x}$S$_{x}$(x=0.25, 35at.%), the amount of refractive index change $\Delta$n reaches 0.01~0.53 at 6328, 7800$\AA$ by exposing for 15minutes plue-pass filtered mercury lamp(~4300$\AA$) and annealing 20$0^{\circ}C$. And in initially annealed As$_{40}$ Ge$_{10}$Se$_{15}$ S$_{35}$, photodarkening(PD) and thermalbleaching(TB) was founded.ded.B) was founded.d.

• Transactions on Electrical and Electronic Materials
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• v.5 no.6
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• pp.219-222
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• 2004

This paper discovers that there are some peculiar properties that can remove holography grating, which was made in chacogenide thin film by impressed voltage. The thin films were used are $As_{40}Ge_{10}Se_{15}S_{35}$, and we use He-Ne laser in order to form thin films. I-V curved line in a thin film before a lattice was made has the critical point, about 3.7 V. Moreover, the I-V curved line increased current intensity at over 4 V after it made thin film. In addition, while holography grating is being made, and when it has the highest diffraction efficiency, a lattice can be deleted if put more voltage into it.

• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.11a
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• pp.77-81
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• 1992

The purpose of this research was th evaluate conductivity of electricity of Ge-Se-Bi system Chalcogenide glass as a amorphous semiconductor by observing its dissolution and crystallization. In this experiment. Ge-Se-Bi metal powder in the rage of $Ge_{12-25}$, $Se_{65-85}$, $Bi_{2.5-15}$ was used as the sample ore. The ore was. put into a vaccous quartz tube and then melted. The condition of heat treatment was to dispose it to $1000^{\circ}C$ heat for 10 hours and then rapidly quenched it at $3834^{\circ}C$/see. The crystallization of the fused sample ripened as the change of temperature and time, after the crystal core was formell. At that time it was possible to observe the state that $Bi_2Se_3$ and $GeSe_2$ were crystallized. In the experiment of making memberance, the memberance was produced by using the previously experimented bulk sample. And decrystalization was well progressed when Ge was over 15 at %, Se was over 70 at %, and Bi was under 10 at%. As for bulk. when Ge was fixed to 20 at %, the conducting of electricity was increased as Bi gained at %. In the case of memberance, the conductivity was much more increased than that of bulk sample as the increase of at the increase of at % of Bi. In the experiment on $Ge_{20}$, $Se_{77.5}$ and $Bi_{2.5}$, the crystallization sswas most vigorous when they were kept at $330^{\circ}C$ for 4 hours.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.2
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• pp.140-148
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• 1993

In this study, the electrical and optical properties of amorphous, crystallization and thin film of As-Ge-Se Chalcogenide System was investigated. Typical composition of this material has $As_{20~50}Se_{40~70} and Ge_{10~40}$ at%. Materials having Se was fixed to 40 at% and As was above 30 at% much more increased the electrical conductivity. After crystallization at the temperature of $476^{\circ}C$ for 3 hour was showed the best electrical conductivity of 1.74E-13$(\Omega cm)^{-l}$. And the main crystalline phase of this sample can be investigated using the mixed crystalline, i.e, $GeSe_2 and As_2Se_3$ phases. The thin film shows the optical absorption coefficient in the range $2{times}10^3 to 7{times}10^4$ and the optical energy gap of 1.85eV.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.237.2-237.2
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• 2013

ReRAM cell, also known as conductive bridging RAM (CBRAM), is a resistive switching memory based on non-volatile formation and dissolution of conductive filament in a solid electrolyte [1,2]. Especially, Chalcogenide-based ReRAM have become a promising candidate due to the simple structure, high density and low power operation than other types of ReRAM but the uniformity of switching parameter is undesirable. It is because diffusion of ions from anode to cathode in solid electrolyte layer is random [3]. That is to say, the formation of conductive filament is not go through the same paths in each switching cycle which is one of the major obstacles for performance improvement of ReRAM devices. Therefore, to control of nonuniform conductive filament formation is a key point to achieve a high performance ReRAM. In this paper, we demonstrated the enhanced repeatable bipolar resistive switching memory characteristics by spreading the Ag nanocrystals (Ag NCs) on amorphous GeSe layer compared to the conventional Ag/GeSe/Pt structure without Ag NCs. The Ag NCs and Ag top electrode act as a metal supply source of our devices. Excellent resistive switching memory characteristics were obtained and improvement of voltage distribution was achieved from the Al/Ag NCs/GeSe/Pt structure. At the same time, a stable DC endurance (>100 cycles) and an excellent data retention (>104 sec) properties was found from the Al/Ag NCs/GeSe/ Pt structured ReRAMs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.3
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• pp.133-138
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• 2017

We evaluated the structural, electrical and optical properties of tungsten (W)-doped $Ge_8Sb_2Te_{11}$ thin films. In a previous work, GeSbTe alloys were doped with different materials in an attempt to improve thermal stability. 200 mm thick $Ge_8Sb_2Te_{11}$ and W-doped $Ge_8Sb_2Te_{11}$ films were deposited on p-type Si (100) and glass substrates using a magnetron co-sputtering system at room temperature. The fabricated films were annealed in a furnace in the $0{\sim}400^{\circ}C$ temperature range. The structural properties were analyzed using X-ray diffraction (X'pert PRO, Phillips). The results showed increased crystallization temperature ($T_c$) leading to thermal stability in the amorphous state. The optical properties were analyzed using an UV-Vis-IR spectrophotometer (Shimadzu, U-3501, range : 300~3,000 nm). The results showed an increase in the crystalline material optical energy band gap ($E_{op}$) and an increase in the $E_{op}$ difference (${\Delta}E_{op}$). This is a good effect to reduce memory device noise. The electrical properties were analyzed using a 4-point probe (CNT-series). This showed increased sheet resistance ($R_s$), which reduces programming current in the memory device.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.976-979
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• 2003

In this study, we formed the 2-dimensional holographic grating in order to mamufactured 2-dimensional photonic crystal in amorphous $As_{40}Ge_{10}Se_{15}S_{35}$ and $Ag/As_{40}Ge_{10}Se_{15}S_{35}$ thin film which have the excellent optical sensetivity using by He-Ne laser(632.8nm). The intensity of incident beam was 2.5mW and incident angle that $2{\theta}$ is $20^{\circ}$. We formed the holographic grating after had formed the 1-dimansional holographic grating and then rotate the sample. We confirmed that 2-dimensional holographic grating result of the figure of diffracted beam and AFM(Atomic Forced Microcopy) image.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.215-215
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• 2010

The feasibility of InSbTe (IST) chalcogenide materials prepared by metalorganic chemical vapor deposition (MOCVD) for phase-change memory (PRAM) applications was demonstrated. Films grown below $225^{\circ}C$ exhibited an amorphous structure, and the films grown at $300^{\circ}C$ Cincluded various crystalline phases such as In-Sb-Te, In-Sb, In-Te, and Sb-Te. The composition of the amorphous films grown at $225^{\circ}C$ was dependent on the working pressure. Films grown at $225^{\circ}C$ exhibited a smooth morphology with a root mean square(rms) roughness of less than 1nm, and the step-coverage of the films grown on a trench structure with an aspect ratio of 5:1 was greater than 90%. An increase in deposition time increased the filling rate, while retaining the conformal step-coverage. Films grown at $225^{\circ}C$ for 3h in a working pressure of $13{\times}10^2$ Pa exhibited a reproducible and complete filling in a trench structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.71-72
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• 2009

칼코게나이드(chalcogenide)계 비정질 반도체는 그들의 독특한 광학적, 전기적 특성 때문에 활발한 연구가 진행되고 있다. 비정질 Se는 유연한 원자구조로 인해 가장 먼저 광학적으로 상용화되었으며, 응용성이 매우 큰 반도체 재료중 하나로 Ge-Se와 같이 Se를 기본으로 한 칼코게나이드 유리 반도체가 주목받고 있다. 따라서 본 연구에서는 비정질 칼코게나이드 $Ge_xSe_{100-x}$(x=25,95) 조성에 대한 광학적 특성을 연구 하였다. 시료는 5N의 순도를 갖는 Ge, Se 물질을 준비하고 조성비에 맞추어서 석영관에 진공 봉입한 후 용융 혼합하여 $Ge_{25}Se_{75}$와 $Ge_{95}Se_5$조성의 두 가지 비정질 벌크를 제작하였다. 열증착 방법으로 유리 기판위에 박막을 제작하였고 UV-vis-NIR spectrophotometer를 사용하여 투과도를 측정하였다. 측정한 스펙트럼을 이용하여 Swanpoel method로 굴절률을 계산하고 특성을 분석하였다.