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Structural, magnetic, and thermoelectric properties of 3d transition metal arsenide and silicide thin films : Structural, magnetic, and thermoelectric properties of 3d transition metal arsenide and silicide thin films 원문보기

  • 저자

    신유리미

  • 학위수여기관

    울산대학교

  • 학위구분

    국내박사

  • 학과

    물리학과 solid state physics

  • 지도교수

    조성래

  • 발행년도

    2014

  • 총페이지

    86

  • 키워드

    MBE thin film thermoelectric;

  • 언어

    eng

  • 원문 URL

    http://www.riss.kr/link?id=T13540282&outLink=K  

  • 초록

    Bulk 3d transition metal arsenides and silicides materials are already well known as a magnetic and thermoelectric material. In this thesis, we have studied about a MBE (molecular beam epitaxy) growth of CoAs2, FeAs2, CoAs, FeAs, CrAs, MnAs, and FeSi thin films on Si(111) substrate and their structural, magnetic, and thermoelectric properties. Huge thermoelectric power factors of 545, 105, 528, 341, and 274 mW/K2m were observed in the temperature range of 120~350 K for 100 nm-thick, n-type, polycrystalline films of CoAs2, FeAs2, CoAs, FeAs, and CrAs grown on Si(111) substrate, respectively. We found that thermal stress due to thermal expansion coefficient difference between Si and film induced structural deformation, which modified the electronic structure for high carrier mobility and high Seebeck coefficient, resulting in huge power factor. We also observed that below a certain temperature, the electronic structure of the films changed from semiconductor to (semi)metal, due to an increase in thermal strain, which was confirmed via LDA (Local density approximation) electronic structure calculation. The growth and ferromagnetic properties of ε-FeSi thin film on Si(100) substrate prepared by molecular beam epitaxy are reported. The interdiffusion of Fe layer on Si(100) substrate at 600 oC results in polycrystalline ε-FeSi layer. The determined activation energy was 0.044eV. The modified magnetism from paramagnetic in bulk to ferromagnetic states in ε-FeSi thin films was observed. The saturated magnetization and coercive field of ε-FeSi film are 4.6 emu/cm3 and 29 Oe at 300 K, respectively. These results can play an important role in a magnetic and thermoelectric field.


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