Journal of the Korean Institute of Electrical and Electronic Material Engineers (한국전기전자재료학회논문지)

The Korean Institute of Electrical and Electronic Material Engineers (한국전기전자재료학회)
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Characteristics of Cu-Doped Ge8Sb2Te11 Thin Films for PRAM

PRAM용 Cu-도핑된 Ge8Sb2Te11 박막의 특성

  • Kim, Yeong-Mi (Department of Advanced Chemicals and Engineering, Chonnam National University) ;
  • Kong, Heon (Department of Advanced Chemicals and Engineering, Chonnam National University) ;
  • Kim, Byung-Cheul (Department of Electronic Engineering, Gyeongnam National University of Science and Technology) ;
  • Lee, Hyun-Yong (School of Chemical Engineering, Chonnam National University)
  • 김영미 (전남대학교 신화학소재공학과) ;
  • 공헌 (전남대학교 신화학소재공학과) ;
  • 김병철 (경남과학기술대학교 전자공학과) ;
  • 이현용 (전남대학교 화학공학부)
  • Received : 2019.07.08
  • Accepted : 2019.07.27
  • Published : 2019.09.01
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Abstract

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.

Keywords

References

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