Journal of the Microelectronics and Packaging Society (마이크로전자및패키징학회지)

The Korean Microelectronics and Packaging Society (한국마이크로전자및패키징학회)
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The Effects of ZnO Sub-layer Thickness on the Room Temperature Ferromagnetism of (ZnO/Co) Multilayer

(ZnO/Co) 다층 박막에서 ZnO층의 두께가 상온강자성 특성에 미치는 영향

  • 강성근 (앰코테크놀로지코리아(주)) ;
  • 김성동 (서울과학기술대학교 기계시스템디자인공학과)
  • Received : 2018.12.11
  • Accepted : 2018.12.28
  • Published : 2018.12.31
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Abstract

Room temperature ferromagnetism of Co doped ZnO was studied using (ZnO/Co) multilayer structure, and the effects of ZnO sub-layer thickness on the RT ferromagnetism was investigated. As for the as-deposited state, the diamagnetism was observed for ($ZnO\;20{\AA}/Co\;x{\AA}$) while the ferromagnetism was observed for ($ZnO\;40{\AA}/Co\;x{\AA}$). After vacuum-annealed, both showed the RT ferromagnetism and ($ZnO\;40{\AA}/Co\;x{\AA}$) structure interestingly showed negative remanence magnetization behavior. UV-Vis spectrometer revealed that Co atoms were substituted with Zn in ZnO and Co cluster was not found in XPS and HRTEM EDS analysis.

(ZnO/Co) 다층박막 구조를 이용하여 Co 도핑한 ZnO의 상온강자성 특성을 조사하였으며, 특히 ZnO 박막층의 두께가 (ZnO/Co) 다층박막의 상온강자성 특성에 미치는 영향을 조사하였다. ZnO 박막층의 두께가 $20{\AA}$, $40{\AA}$일 때 증착상태에서는 각각 반자성과 강자성 특성을 나타내었으며 진공열처리 후에는 모두 강자성 특성을 나타내었다. 특히 ($ZnO\;40{\AA}/Co\;x{\AA}$)는 열처리 후에 음의 잔류자화 거동을 나타내었다. UV-Vis 분석을 통해서 Co 일부가 Zn와 치환되어 위치하고 있음을 확인할 수 있었으며, 열처리 전후에 대한 XPS 및 HRTEM EDS 분석에서 Co 클러스터의 형성은 관찰되지 않았다.

Keywords

MOKRBW_2018_v25n4_137_f0001.png 이미지

Fig. 1. Schematic diagram for origins of room temperature ferromagnetism in dilute magnetic semiconductor.

MOKRBW_2018_v25n4_137_f0002.png 이미지

Fig. 2. Room temperature magnetization curves for (ZnO 20Å/Co xÅ) multilayer (a) as-deposited (b) vacuum-annealed at 400℃ for 1 hour, and for (ZnO 40Å/Co xÅ) multilayer (c) as-deposited (d) vacuum-annealed at 400℃ for 1 hour.

MOKRBW_2018_v25n4_137_f0003.png 이미지

Fig. 3. UV-Vis transmission of (ZnO 20Å/Co xÅ) multilayer (a) as-deposited (b) vacuum-annealed at 400℃

MOKRBW_2018_v25n4_137_f0004.png 이미지

Fig. 4. XPS depth profiles of (ZnO 20Å/Co 3Å) multilayer (a) as-deposited (b) vacuum-annealed at 400℃

MOKRBW_2018_v25n4_137_f0005.png 이미지

Fig. 5. HRTEM EDS analysis of (ZnO 20Å/Co 3Å) multilayer (a) as-deposited (b) vacuum-annealed at 400℃for 1 hour, and (ZnO 40Å/ Co 3Å) multilayer (c) as-deposited (d) vacuum-annealed at 400℃for 1 hour.

Table 1. (ZnO/Co)/ZnO multilayer specification.

MOKRBW_2018_v25n4_137_t0001.png 이미지

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