• Title/Summary/Keyword: InGeTe

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Amorphous-to-Crystalline Phase Transition of (InTe)x(GeTe) Thin Films ((InTe)x(GeTe) 박막의 비정질-결정질 상변화)

  • Song, Ki-Ho;Beak, Seung-Cheol;Lee, Hyun-Yong
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.3
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    • pp.199-205
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    • 2010
  • The crystallization speed (v) of amorphous (InTe)$_x$(GeTe) (x = 0.1, 0.3 and 0.5) films and their thermal, optical and electrical behaviors have been investigated using nano-pulse scanner (wavelength = 658 nm, laser beam diameter < 2 ${\mu}m$), X-ray diffraction (XRD), 4-point probe and UV-vis-IR spectrophotometer. These results were compared with those of $Ge_2Sb_2Te_5$ (GST) film, comprehensively utilized for phase-change random access memory (PRAM). Both v-value and thermal stability of (InTe)$_{0.1}$(GeTe) and (InTe)$_{0.3}$(GeTe) films could be enhanced in comparison with those of the GST. Contrarily, the v-value in the (InTe)$_{0.5}$(GeTe) film was so drastically deteriorated that we could not quantitatively evaluate it. This deterioration is thought because amorphous (InTe)$_{0.5}$(GeTe) film has relatively high reflectance, resulting in too low absorption to cause the crystallization. Conclusively, it could be thought that a proper compositional (InTe)$_x$(GeTe) films (e.g., x < 0.3) may be good candidates with both high crystallization speed and thermal stability for PRAM application.

An evaluation on crystallization of amorphous (InTe)x(GeTe)y thin films by nano-pulse illumination (나노-펄스 노출에 따른 비정질(InTe)x(GeTe)y박막의 결정화 속도 평가)

  • Song, Ki-Ho;Seo, Jae-Hee;Lee, Hyun-Yong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.11a
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    • pp.419-420
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    • 2008
  • In this work, we report several experimental data capable of evaluating the phase transition characteristics of (InTe)x(GeTe)y (x = 0.1, 0.3, y =1) pseudo-binary thin films. (InTe)x(GeTe)y phase change thin films have been prepared by thermal evaporator. The crystallization characteristics of amorphous (InTe)x(GeTe)y thin films were investigated by using nano-pulse scanner with 658 nm laser diode (power : 1~17 mW, pulse duration : 10~460 ns) and XRD measurement. It was found that the crystalline speed of In-Ge-Te thin films are faster than $Ge_2Sb_2Te_5$[1] and also the crystalline temperature is higher. Changes in the optical transmittance of as-deposited and annealed films were measured using a UV-VIS-IR spectrophotometer and four-point probe was used to measure the sheeresistance of InGeTe films annealed at different temperature.

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Fabrication and Structural Properties of Ge-Sb-Te Thin Film by MOCVD for PRAM Application (상변화 메모리 응용을 위한 MOCVD 방법을 통한 Ge-Sb-Te 계 박막의 증착 및 구조적인 특성분석)

  • Kim, Ran-Young;Kim, Ho-Gi;Yoon, Soon-Gil
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.21 no.5
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    • pp.411-414
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    • 2008
  • The germanium films were deposited by metal organic chemical vapor deposition using $Ge(allyl)_4$ precursors on TiAlN substrates. Deposition of germanium films was only possible with a presence of $Sb(iPr)_3$, which means that $Sb(iPr)_3$ takes a catalytic role by a thermal decomposition of $Sb(iPr)_3$ for Ge film deposition. Also, as Sb bubbler temperature increases, deposition rate of the Ge films increases at a substrate temperature of $370^{\circ}C$. The GeTe thin films were fabricated by MOCVD with $Te(tBu)_2$ on Ge thin film. The GeTe films were grown by the tellurium deposition at $230-250^{\circ}C$ on Ge films deposited on TiAlN electrode in the presence of Sb at $370^{\circ}C$. The GeTe film growth on Ge films depends on the both the tellurium deposition temperature and deposition time. Also, using $Sb(iPr)_3$ precursor, GeSbTe films with hexagonal structures were fabricated on GeTe thin films. GeSbTe films were deposited in trench structure with 200 nm*120 nm small size.

STM investigation of as-cleaved and annealed single crystalline GeTe (111) surface

  • Kim, Ji-ho;Choi, Hoon-hee;Chung, In;Lyo, In-Whan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.140.2-140.2
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    • 2016
  • Despite the growing interest in GeTe as a archetypal displacive ferroelectric material as well as the basis of related materials used in data-storage applications, atom-resolved study of single crystalline GeTe surface been lacking. Using low temperature scanning tunneling microscopy (STM) and spectroscopy (STS), we investigated as-cleaved and annealed surfaces of GeTe. We found that as-cleaved GeTe(111) surface is composed of at least two kinds of terraces at 78 K. While two terraces show metallic characteristics, they also exhibit distinctive I-V spectra and imaging conditions, with each being attributed to Ge-terminated, and Te-terminated surfaces respectively. GeTe(111) surfaces annealed at moderately elevated temperature introduces intricate networks of extended defect structures. We will present these data and discuss the role of vacancies in the formation of these structures.

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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.

A Study on the Electrical Properties of MIM Structures Based on Ge2Sb2Te5 and Ge8Sb2Te11 Thin Films for ReRAM (ReRAM응용을 위한 Ge2Sb2Te5와 Ge8Sb2Te11 기반 MIM구조 박막의 전기적 특성 연구)

  • Jang, Hwi-Jong;Kong, Heon;Yeo, Jong-Bin;Lee, Hyun-Yong
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.30 no.3
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    • pp.144-147
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    • 2017
  • In this study, $Ge_2Sb_2Te_5$ and $Ge_8Sb_2Te_{11}$ were used as an insulator layer to fabricate ReRAM devices. The resistance change is correlated to the appearance or disappearance of a conductivity filament at the surface of the GeSbTe layer. Changes in the electrical properties of ITO/GeSbTe/Ag devices were measured using a I-V-L measurement system. As a result, compared to the $ITO/Ge_8Sb_2Te_{11}/Ag$ device, this $ITO/Ge_2Sb_2Te_5/Ag$ ReRAM device exhibits highly uniform bipolar resistive switching characteristics, such as the operating voltages, and the resistance values.

Properties and Crystallization Characteristics of Ge-Se-Te Glasses (Ge-Se-Te계 칼코지나이드 유리의 결정 생성 현상 및 특성)

  • Lee, Yong-Woo;Heo, Jong
    • Journal of the Korean Ceramic Society
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    • v.32 no.2
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    • pp.239-247
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    • 1995
  • Chalcogenide glasses with compositions of Ge10Se90-xTex(X=0~50 at.%) were prepared in order to investigate the effects of Te substitution on the transmission characteristics of Ge-Se glasses in the 8~12 ${\mu}{\textrm}{m}$ wavelength region. Absorption coefficients were observed to decrease with Te addition, indicating the improved transmission capabilities of Ge-Se-Te glasses as compared to binary Ge-Se glasses. XRD analysis of crystallized glasses suggested the formation of weaker Se-Te and/or Te-Te bonds with addition of Te substituting for Se in stronger Se-Se bonds. Incorporation of Te in excess of 20at% resulted in the formation of hexagonal Te phases when crystallized. It is speculated that the presence of Te-Te bonds with highly metallic bond character resulted in the enhanced crystallization tendencies of glasses. Fromation of Te-rich chains through gradual replacement of Se-Se with Se-Te and/or Te-Te bonds was further supported by decreases in glass transition and crystallization temperatures.

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Real time control of the growth of Ge-Sb-Te multi-layer film as an optical recording media using in-situ ellipsometry (In-situ ellipsometry를 사용한 광기록매체용 Ge-Sb-Te 다층박막성장의 실시간 제어)

  • 김종혁;이학철;김상준;김상열;안성혁;원영희
    • Korean Journal of Optics and Photonics
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    • v.13 no.3
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    • pp.215-222
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    • 2002
  • Using an in-situ ellipsometer, we monitored the growth curve of optical recording media in real time. For confirmation of the thickness control using in-situ ellipsometry, we analyzed the deposited multi-layer sample made of Ge-Sb-Te alloy film and ZnS-Si0$_2$ dielectric films using an exsitu spectroscopic ellipsometer. The target material in the first sputtering gun is ZnS-SiO$_2$ as the protecting dielectric layer and that in the second gun is Ge$_2$sb$_2$Te$_{5}$ as the receding layer. While depositing ZnS-SiO$_2$, Ge$_2$Sb$_2$Te$_{5}$ and ZnS-SiO$_2$ films on c-Si substrate in sequence, we measured Ψ $\Delta$ in real time. Utilizing the complex refractive indices of Ge$_2$Sb$_2$Te$_{5}$ and ZnS-SiO$_2$ obtained from the analysis of spectroscopic ellipsometry data, the evolution of ellipsometric constants Ψ, $\Delta$ with thickness is calculated. By comparing the calculated evolution curve of ellipsometric constants with the measured one, and by analyzing the effect of density variation of the Ge$_2$Sb$_2$Te$_{5}$ recording layer on ellipsometric constants with thickness, we precisely monitored the growth rate of the Ge-Sb-Te multilayer and controlled the growth process. The deviation of the real thicknesses of Ge-Sb-Te multilayer obtained under the strict monitoring is post confirmed to be less than 1.5% from the target structure of ZnS-SiO$_2$(1400 $\AA$)IGST(200 $\AA$)$\mid$ZnS-SiO$_2$(200$\AA$).(200$\AA$).

Effect of Annealing Temperature on Phase-change Characteristics of GeSbTe-based Bilayers (GeSbTe계 이중층의 상변화 특성에 미치는 열처리 온도 효과)

  • 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.30 no.2
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    • pp.86-90
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    • 2017
  • This work reports the phase-change behavior and thermal stability of doped GeSbTe/GeSbTe bilayers. We prepared the bilayers using RF sputtering, and annealed them at annealing temperature ranging from $100^{\circ}C$ to $400^{\circ}C$. The sheet resistance of the bilayer decreased and saturated with increasing annealing temperature, and the saturated value was close to that of pure GeSbTe film. The surface of the bilayer roughened at $400^{\circ}C$, which corresponds to the surface roughening of doped GeSbTe film. Mixed phases of face-centered cubic and hexagonal close-packed crystalline structures were identified in the bilayers annealed at elevated temperature. These results indicate that the phase-change behavior of the bilayer depends on the concurrent phase-transitions of the two GeSbTe-based films. The dopants in the doped GeSbTe film were diffused out at annealing temperatures of $300^{\circ}C$ or higher, which implies that the thermal stability of the bilayer should be considered for its application in phase-change electronic devices.

Phase Change Properties of Amorphous Ge1Se1Te2 and Ge2Sb2Te5 Chalcogenide Thin Films (비정질 Ge1Se1Te2 과 Ge2Sb2Te5 칼코게나이드 박막의 상변화특성)

  • Chung Hong-Bay;Cho Won-Ju;Ku Sang-Mo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.10
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    • pp.918-922
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    • 2006
  • Chalcogenide Phase change memory has the high performance necessary for next-generation memory, because it is a nonvolatile memory with high programming speed, low programming voltage, high sensing margin, low power consumption and long cycle duration. To minimize the power consumption and the program voltage, the new composition material which shows the better phase-change properties than conventional $Ge_2Sb_2Te_5$ device has to be needed by accurate material engineering. In the present work, we investigate the basic thermal and the electrical properties due to phase-change compared with chalcogenide-based new composition $Ge_1Se_1Te_2$ material thin film and convetional $Ge_2Sb_2Te_5$ PRAM thin film. The fabricated new composition $Ge_1Se_1Te_2$ thin film exhibited a successful switching between an amorphous and a crystalline phase by applying a 950 ns -6.2 V set pulse and a 90 ns -8.2 V reset pulse. It is expected that the new composition $Ge_1Se_1Te_2$ material thin film device will be possible to applicable to overcome the Set/Reset problem for the nonvolatile memory device element of PRAM instead of conventional $Ge_2Sb_2Te_5$ device.