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Studies on Electrical and Structural Properties in Oxygen Level Controlled BaSnO3-d Single Crystals
산소 조성 조절에 따른 BaSnO3-d 단결정의 전기적 및 구조적 특성에 관한 연구

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dc.contributor.advisor김기훈-
dc.contributor.author손이곤-
dc.date.accessioned2017-07-19T09:10:47Z-
dc.date.available2017-07-19T09:10:47Z-
dc.date.issued2014-08-
dc.identifier.other000000021504-
dc.identifier.urihttp://hdl.handle.net/10371/131626-
dc.description학위논문 (석사)-- 서울대학교 대학원 : 물리·천문학부, 2014. 8. 김기훈.-
dc.description.abstractTransparent conducting oxides are gaining more interest because of its importance in display-related applications, photovoltaic, energy efficient windows and so on. Indium tin oxide, fluorine doped tin oxide and aluminium doped zinc oxides are the most widely used compounds in this field. However, they have drawbacks as well, such as high cost and oxygen instability issues. Our group previously succeeded in growing the single crystal of a possible replacement, BaSnO3. The physical properties of perovskite structured barium stannate single crystals, BaSnO3, (Ba,La)SnO3, and Ba(Sn,Sb)O3 were studied thoroughly. Especially, (Ba,La)SnO3 has exhibited high mobility, 320 cm2V- 1S-1, while maintaining its transparency. Also, there were efforts to grow (Ba,La)SnO3 film with high mobility, but due to the lattice mismatch between (Ba,La)SnO3 and the substrate, the mobility remained low, 70 cm2V-1s-1. Thus, undoped BaSnO3 comes in fore as a lattice-matched substrate. However, previous data show that undoped BaSnO3 has a carrier concentration of ~1018 cm-3 by the presence of oxygen vacancy.
In this thesis, we present that we successfully reduced oxygen vacancy in undoped BaSnO3 crystals by adding an oxidizer during flux growth. The crystals are confirmed to be an identical cubic perovskite with a lattice parameter of a=b=c=4.117 Å. The reduction of oxygen vacancy led to a metal-insulator transition where the resistivity changed drastically from ~10-3 Ω∙cm to ~1011 Ω∙cm at room temperature. The crystals with low resistivity were blue in color while the crystals with high resistivity were yellow. By optical spectroscopy ranging from mid-IR to UV, we observed that crystals grown with an oxidizer have significantly lower free carrier absorption. Moreover, through Raman spectroscopy, we noticed that the
BaSnO3-d crystals show first-order Raman scattering which means that it is locally distorted even though the x-ray diffraction pattern shows a cubic perovskite structure. This may indicate that the presence of carrier in BaSnO3-d single crystal is closely related to local structure distortion. Through polarized Raman spectroscopy, we attempted to assign the observed first order Raman peaks. Additionally, we have investigated the external effects, such as polishing and forming gas annealing, on the structure of BaSnO3-d single crystals through Raman spectroscopy. In all, this dissertation focuses on the physical properties of BaSnO3-d single crystals while modifying the oxygen vacancy level by the use of an oxidizer.
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dc.description.tableofcontentsAbstract .................................................................................. i Contents................................................................................. iii
List of Figures ......................................................................... v
List of Tables ......................................................................... vii
1 Introduction........................................................................ 1
2 Fundamentals ..................................................................... 5
2.1 Crystal structure and measurement ................................. 5
2.1.1 Periodic structure and reciprocal space ....................... 5
2.1.2 Bragg condition and X-ray diffraction ......................... 7
2.2 Electrical transport properties ........................................ 10
2.3 Optical properties .......................................................... 13
2.4 Raman spectroscopy....................................................... 17
2.4.1 General....................................................................... 17
2.4.2 Polarized Raman spectroscopy.....................................21
2.4.3 Raman scattering intensity.......................................... 26
3 Experimental Details .......................................................... 28
3.1 Single crystal growth....................................................... 28
3.2 Structure analysis ........................................................... 30
3.3 Electrical transport ......................................................... 30
3.4 Optical transmission ....................................................... 31
3.5 Raman spectroscopy........................................................ 32
4 Results and Discussions....................................................... 33
4.1 Structure analysis ........................................................... 33
4.1.1 X-ray diffraction ......................................................... 33
4.1.2 X-ray microdiffraction................................................. 35
4.2 Electrical transport ......................................................... 37
4.2.1 Temperature dependent resistivity................................37
4.3 Optical transmission.........................................................45
4.4 Raman spectroscopy........................................................ 50
4.4.1 BaSnO3-d Single crystals............................................. 50
4.4.2 External effect on crystal structure................................57
4.4.3 Doped BaSnO3 single crystals.......................................62
5 Conclusion ......................................................................... 64
Reference ............................................................................... 66
국문 초록....................................................................................68
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dc.formatapplication/pdf-
dc.format.extent2760718 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectransparent conducting oxides-
dc.subjectBaSnO3-
dc.subjectcubic perovskite-
dc.subjectRaman spectroscopy-
dc.subject.ddc523-
dc.titleStudies on Electrical and Structural Properties in Oxygen Level Controlled BaSnO3-d Single Crystals-
dc.title.alternative산소 조성 조절에 따른 BaSnO3-d 단결정의 전기적 및 구조적 특성에 관한 연구-
dc.typeThesis-
dc.description.degreeMaster-
dc.citation.pages68-
dc.contributor.affiliation자연과학대학 물리·천문학부-
dc.date.awarded2014-08-
Appears in Collections:
College of Natural Sciences (자연과학대학)Dept. of Physics and Astronomy (물리·천문학부)Physics (물리학전공)Theses (Master's Degree_물리학전공)
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