• Title, Summary, Keyword: $Ge_8Sb_2Te_{11}$

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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.

Effect of tungsten on the phase-change properties of Ge8Sb2Te11 Thin Films for the Phase-change device

  • Park, Cheol-Jin;Kong, Heon;Lee, Hyun-Yong;Yeo, Jong-Bin
    • Journal of the Korean Physical Society
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    • v.71 no.1
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    • pp.42-46
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    • 2017
  • In this study, the electrical, optical, and structural properties of tungsten (W)-doped $Ge_8Sb_2Te_{11}$ thin films were investigated. Previously, GeSbTe alloys were doped with various materials in an attempt to improve the thermal stability. $Ge_8Sb_2Te_{11}$ and W-doped $Ge_8Sb_2Te_{11}$ films with a thickness of 200 nm were fabricated by using an RF magnetron reactive co-sputtering system at room temperature on Si (p-type, 100) and glass substrate. The fabricated thin films were annealed in a furnace in the ${\sim}0-400^{\circ}C$ temperature range. The optical properties were analyzed using a UV-Vis-IR spectrophotometer, and by using Beer's Law equation, the optical-energy band gap ($E_{op}$), slope $B^{1/2}$, and slope 1/F were calculated. For the crystalline materials, an increase in the slope $B^{1/2}$ and 1/F was observed, exhibiting a good effect on the thermal stability in the amorphous state after the phase change. The structural properties were analyzed by X-ray diffraction, and the result showed that the W-doped $Ge_8Sb_2Te_{11}$ had a face-centered-cubic (fcc) crystalline structure increased crystallization temperature ($T_c$). An increase in the $T_c$ increased the thermal stability in the amorphous state. The electrical properties were analyzed using a 4-point probe, exhibiting an increase in the sheet resistance ($R_s$) in the amorphous and the crystalline states indicating a reduced programming current in the memory device.

A Study On Properties and Phase Change Characteristics of (GeTe)x(Sb2Te3) (x=0.5, 1, 2, 8) Thin Films for PRAM (PRAM을 위한 (GeTe)x(Sb2Te3) (x=0.5, 1, 2, 8) 박막의 물성 및 상변환 특성 연구)

  • Kim, Sung-Won;Song, Ki-Ho;Lee, Hyun-Yong
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.21 no.7
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    • pp.585-593
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    • 2008
  • In this work, we report several experimental data capable of evaluating the phase transformation characteristics of GeSbTe pseudobinary thin films comprehensively utilized as phase change materials. The phase transformation of the GeSbTe thin films was confirmed by XRD measurement from amorphous to hexagonal structure via fee structure except for $Ge_8Sb_2Te_{11}$. In addition, X-ray photoelectron spectra analysis revealed to weaken Ge-Te bond for $Ge_2Sb_2Te_5$ and to strengthen the bonds of all elements for $Ge_8Sb_2Te_{11}$ during the amorphous to crystalline transition. The values of optical energy gap $(E_{OP})$ were around 0.71 and 0.50 eV and the slopes of absorption in extended region (B) were ${\sim}5.1{\times}10^5$ and ${\sim}10{\times}10^5cm^{-1}{\cdot}V^{-1}$ for the amorphous and fcc-crystalline structures, respectively. Finally, the kinetics of amorphous-to-crystalline phase change on the GeSbTe films was characterized using a nano-pulse scanner with 658-nm laser diode (power; $1{\sim}17$ mW, pulse duration; $10{\sim}460$ ns).

Evaluation on the Phase-Change Properties in W-doped Ge8Sb2Te11 Thin Films for Amorphous-to-Crystalline Reversible Phase-Change Device (비정질-결정질 가역적 상변환 소자용 Ge8Sb2Te11 박막의 W 도핑에 따른 상변환 특성 평가)

  • Park, Cheol-Jin;Yeo, Jong-Bin;Kong, Heon;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.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.

Characteristics of Cu-Doped Ge8Sb2Te11 Thin Films for PRAM (PRAM용 Cu-도핑된 Ge8Sb2Te11 박막의 특성)

  • Kim, Yeong-Mi;Kong, Heon;Kim, Byung-Cheul;Lee, Hyun-Yong
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.32 no.5
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    • pp.376-381
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    • 2019
  • In this work, we evaluated the structural, electrical and optical properties of $Ge_8Sb_2Te_{11}$ and Cu-doped $Ge_8Sb_2Te_{11}$ thin films prepared by rf-magnetron reactive sputtering. The 200-nm-thick deposited films were annealed in a range of $100{\sim}400^{\circ}C$ using a furnace in an $N_2$ atmosphere. The amorphous-to-crystalline phase changes of the thin films were investigated by X-ray diffraction (XRD), UV-Vis-IR spectrophotometry, a 4-point probe, and a source meter. A one-step phase transformation from amorphous to face-centered-cubic (fcc) and an increase of the crystallization temperature ($T_c$) was observed in the Cu-doped film, which indicates an enhanced thermal stability in the amorphous state. The difference in the optical energy band gap ($E_{op}$) between the amorphous and crystalline phases was relatively large, approximately 0.38~0.41 eV, which is beneficial for reducing the noise in the memory devices. The sheet resistance($R_s$) of the amorphous phase in the Cu-doped film was about 1.5 orders larger than that in undoped film. A large $R_s$ in the amorphous phase will reduce the programming current in the memory device. An increase of threshold voltage ($V_{th}$) was seen in the Cu-doped film, which implied a high thermal efficiency. This suggests that the Cu-doped $Ge_8Sb_2Te_{11}$ thin film is a good candidate for PRAM.

Electrical Switching Characteristics of Ge1Se1Te2 Chalcogenide Thin Film for Phase Change Memory

  • Lee, Jae-Min;Yeo, Cheol-Ho;Shin, Kyung;Chung, Hong-Bay
    • Transactions on Electrical and Electronic Materials
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    • v.7 no.1
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    • pp.7-11
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    • 2006
  • The changes of the electrical conductivity in chalcogenide amorphous semiconductors, $Ge_{1}Se_{1}Te_{2}$, have been studied. A phase change random access memory (PRAM) device without an access transistor is successfully fabricated with the $Ge_{1}Se_{1}Te_{2}$-phase-change resistor, which has much higher electrical resistivity than $Ge_{2}Sb_{2}Te_{5}$ and its electric resistivity can be varied by the factor of $10^5$ times, relating with the degree of crystallization. 100 nm thick $Ge_{1}Se_{1}Te_{2}$ thin film was formed by vacuum deposition at $1.5{\times}10^{-5}$ Torr. The static mode switching (DC test) is tested for the $100\;{\mu}m-sized$ $Ge_{1}Se_{1}Te_{2}$ PRAM device. In the first sweep, the amorphous $Ge_{1}Se_{1}Te_{2}$ thin film showed a high resistance state at low voltage region. However, when it reached to the threshold voltage, $V_{th}$, the electrical resistance of device was drastically reduced through the formation of an electrically conducting path. The pulsed mode switching of the $20{\mu}m-sized$ $Ge_{1}Se_{1}Te_{2}$ PRAM device showed that the reset of device was done with a 80 ns-8.6 V pulse and the set of device was done with a 200 ns-4.3 V pulse.