• Title/Summary/Keyword: 비스무스 박막

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Physical correlation between annealing process and crystal structure and magneto-resistance of Bismuth thin films (열처리 공정과 비스무스 박막의 결정구조 및 자기저항 특성변화와의 물리적 관계)

  • Jang, Seok Woo;Seo, Young-Ho;An, Ho-Myoung
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.18 no.3
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    • pp.638-642
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    • 2014
  • In this study, we investigate on the crystal microstructure and magneto-resistance (MR) change of Bismuth(Bi) thin films for annealing process, in order to apply Bi thin films to the spin electronic devices. As-prepared Bi thin films show the randomly oriented find grains whose size was measured to about 100 nm and the very low MR (4.7 % at room temperature) while careful annealing results in not only grain growth up to ${\sim}2{\mu}m$ but also drastic MR improvement (404 % at room temperature). The drastic change in the MR after applying the annealing process is attributed to the grain growth decreasing grain boundary scattering of electron. Therefore, in this study, we confirm the annealing effect for the grain boundary formation and MR improvement of Bi thin films, and demonstrate the feasibility of spin electronic devices.

Preparation of Bismuth Telluride Thin Films using RF magnetron sputtering and Study on Their Thermoelectric Properties (RF 마그네트론 스퍼터링을 이용한 Bismuth Telluride 박막의 제조와 그 열전 특성 연구)

  • Kim, Dong-Ho;Lee, Gun-Hwan
    • Journal of the Korean Vacuum Society
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    • v.14 no.4
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    • pp.215-221
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    • 2005
  • Thermoelectric bismuth telluride thin films were prepared on $SiO_{2}$/Si substrate with co-sputtering of bismuth and tellurium targets. The effects of deposition temperature on surface morphology, crystallinity and electrical transport properties were investigated. Hexagonal crystallites were clearly visible at the surface of films deposited above $290 ^{\circ}C$. Change of dominant phase from rhombohedral $Bi_2Te_3$ to hexagonal BiTe was confirmed with X-ray diffraction analysis. The deviation from stoichiometric composition at high deposition temperature resulted in the change of structural and electrical characteristics. Seebeck coefficients of all samples have negative value, indicating the prepared $Bi_XTe_Y$ films are n-type thermoelectric. Optimum of Seebeck coefficient and power factor were obtained at the deposition temperature of $225 \^{circ}$C (about -55 $\mu$V/K and $3\times10^{-4}$ W/$k^{2}$m, respectively). Deterioration of thermoelectric properties at higher temperature.

Magnetoresistance in Post-annealed Bi Thin Films on PbTe-buffered CdTe(111)B and on Mica Substrates (PbTe/CdTe(111)B와 마이카 기판 위에 성장된 Bi 박막의 후열처리 전후의 자기저항)

  • Kim Yun-Ki;Choi Jin-Sung;Li Hai-Bo;Cho Sung-Lae
    • Journal of the Korean Vacuum Society
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    • v.15 no.4
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    • pp.367-373
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    • 2006
  • We have observed a large increase in the magnetoresistance (MR) of Bi thin films, which were subjected to a post-annealing procedure at $268^{\circ}C$C, $3^{\circ}C$ below the Bi melting point. We have achieved an increase in the MR by 260-fold and 1200-fold at 5 K and 5 T after post-annealing, as compared with 190 and 620 for an as-deposited Bi film on PbTe/CdTe(111) and on mica, respectively. The large MR increase by post-annealing might be due to the improvement of crystallinity according to the x-ray analysis. However, post-annealing over a certain amount time showed the reduction in MR values.

Low temperature solution growth of silicon on foreign substrates (이종기판을 사용한 저온에서의 실리콘 박막 용액 성장법)

  • Soo Hong Lee;Martin A. Green
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.4 no.1
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    • pp.42-45
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    • 1994
  • Deposition of silicon on pretreated sapphire and glass substrates has been investigated by the solution growth method at low temperatures. An average 14 $\mu\textrm{m}$ thickness of silicon was grown over a large area on sapphire substrate originally coated with a much thinner silicon layer [0.5 $\mu\textrm{m}$ (100) Si/(1102) sapphire)] at low temperatures from $380~460^{\cire}C$. Successful results were obtained from surface treated glass substrates in the temperatures range from $420~520^{\circ}C$.

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Optimization of Bismuth-Based Inorganic Thin Films for Eco-Friend, Pb-Free Perovskite Solar Cells (친환경 Pb-Free 페로브스카이트 태양전지를 위한 비스무스 기반의 무기 박막 최적화 연구)

  • Seo, Ye Jin;Kang, Dong-Won
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.31 no.2
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    • pp.117-121
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    • 2018
  • Perovskite solar cells have received increasing attention in recent years because of their outstanding power conversion efficiency (exceeding 22%). However, they typically contain toxic Pb, which is a limiting factor for industrialization. We focused on preparing Pb-free perovskite films of Ag-Bi-I trivalent compounds. Perovskite thin films with improved optical properties were obtained by applying an anti-solvent (toluene) washing technique during the spin coating of perovskites. In addition, the surface condition of the perovskite film was optimized using a multi-step thermal annealing treatment. Using the optimized process parameters, $AgBi_2I_7$ perovskite films with good absorption and improved planar surface topography (root mean square roughness decreased from 80 to 26 nm) were obtained. This study is expected to open up new possibilities for the development of high performance $AgBi_2I_7$ perovskite solar cells for applications in Pb-free energy conversion devices.

Structural Characterization of Bismuth Zinc Oxide Thin Films Grown by Plasma-Assisted Molecular Beam Epitaxy (플라즈마분자선에피탁시법으로 성장한 산화비스무스아연 박막의 구조특성)

  • Lim, Dong-Seok;Shin, Eun-Jung;Lim, Se-Hwan;Han, Seok-Kyu;Lee, Hyo-Sung;Hong, Soon-Ku;Joeng, Myoung-Ho;Lee, Jeong-Yong;Cho, Hyung-Koun;Yao, Takafumi
    • Korean Journal of Materials Research
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    • v.21 no.10
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    • pp.563-567
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    • 2011
  • We report the structural characterization of $Bi_xZn_{1-x}O$ thin films grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. By increasing the Bi flux during the growth process, $Bi_xZn_{1-x}O$ thin films with various Bi contents (x = 0~13.17 atomic %) were prepared. X-ray diffraction (XRD) measurements revealed the formation of Bi-oxide phase in (Bi)ZnO after increasing the Bi content. However, it was impossible to determine whether the formed Bi-oxide phase was the monoclinic structure ${\alpha}-Bi_2O_3$ or the tetragonal structure ${\beta}-Bi_2O_3$ by means of XRD ${\theta}-2{\theta}$ measurements, as the observed diffraction peaks of the $2{\theta}$ value at ~28 were very close to reflection of the (012) plane for the monoclinic structure ${\alpha}-Bi_2O_3$ at 28.064 and the reflection of the (201) plane for the tetragonal structure ${\beta}-Bi_2O_3$ at 27.946. By means of transmission electron microscopy (TEM) using a diffraction pattern analysis and a high-resolution lattice image, it was finally determined as the monoclinic structure ${\alpha}-Bi_2O_3$ phase. To investigate the distribution of the Bi and Bi-oxide phases in BiZnO films, elemental mapping using energy dispersive spectroscopy equipped with TEM was performed. Considering both the XRD and the elemental mapping results, it was concluded that hexagonal-structure wurtzite $Bi_xZn_{1-x}O$ thin films were grown at a low Bi content (x = ~2.37 atomic %) without the formation of ${\alpha}-Bi_2O_3$. However, the increased Bi content (x = 4.63~13.17 atomic %) resulted in the formation of the ${\alpha}-Bi_2O_3$ phase in the wurtzite (Bi)ZnO matrix.