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Nanopatterned 2D Materials using Block Copolymer Nano-Lithography for Superior Thermoelectrics : 블록공중합체의 나노 구조 제어를 통하여 나노 패턴된 이차원 물질의 열전 성능 극대화에 대한 연구

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dc.contributor.advisor이종찬-
dc.contributor.author오진우-
dc.date.accessioned2018-11-12T00:58:31Z-
dc.date.available2018-11-12T00:58:31Z-
dc.date.issued2018-08-
dc.identifier.other000000152415-
dc.identifier.urihttps://hdl.handle.net/10371/143198-
dc.description학위논문 (박사)-- 서울대학교 대학원 : 공과대학 화학생물공학부, 2018. 8. 이종찬.-
dc.description.abstractThis study presents fabrication and characterization of nano patterned low dimensional materials fabricated from block copolymer (BCP) self-assembly and nano lithography and application to the thermoelectrics. Also the thermoelectric generator from conductive polymer and rubbery BCP is prepared and applied to the self-powered devices. Firstly, universal method to prepare perpendicular BCP nanopattern is introduced. Universal solution for 3 different BCP including polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA), polystyrene-b-polydimethylsiloxane (PS-b-PDMS) and polystyrene-b-poly(2-vinylprydine) (PS-b-P2VP) is adopted to produce perpendicular micro domain. Short time plasma treatment was applied to the top surface of BCP which initiate the crosslinking reaction to produce crosslinking layer. The crosslinking layer exhibits physical immobilization effect to both BCP blocks. The crosslinking layer also applied to the bottom layer replacing random copolymer brush, and the bottom layer can act as a neutral layer to the BCP film. The perpendicular nanopattern from 3 different BCP was observed with scanning electron microscope (SEM) and grazing intensity small angle x-ray scattering (GI-SAXS). BCP with plasma treatment of both top and bottom has fully-perpendicular orientation from the bottom to the top. The crosslinking layer on the top surface is more stiff than neat BCP, the wrinkle is induced after annealing process. In this reason, the thickness of crosslinking layer is controlled by varying the intensity and time of plasma treatment.

Secondary, graphene nano structure was fabricated from BCP self-assembly. The large graphene up to 2 centimeter scale was fabricated from chemical vapor deposition (CVD) and nano patterned using PS-b-P2VP sphere nanopattern. Thermoelectric properties of the graphene nanomesh structure with controlled neck width is enhanced up to 40 times higher than pristine graphene. The Seebeck coefficient of the bilayer graphene nanomesh with 8 nm neck width shows the highest value of ~ 520 μV/K among the graphene-related materials. The thermal conductivity of suspended graphene nanomesh is reduced to ~78 W/m·K which is the lowest thermal conductivity for graphene nanostructure. Classical and quantum mechanical calculations supported my nanomesh approach, which can achieve high thermal properties based on reduced thermal conductivity and higher thermopower due to the confined geometry. Also the heterostructure of graphene nanostructure and transition metal dicalcogenides was introduced. Molybdenum disulfide (MoS2) has extremely high Seebeck coefficient and low thermal conductivity, however, very low electrical conductivity. To enhance the electrical conductivity selectively, graphene nanoribbon is adopted as an electron highways to the MoS2 thin film. The large area graphene nanoribbon was fabrication from block copolymer lithography, and was transferred to the MoS2 atomic layer. The graphene nanostructure significantly enhances the electrical conductivity of the MoS2 atomic layer more than 1000 time higher. We show that with heterostructure, the thermoelectric properties can be enhanced.

Finally, PEDOT:PSS with coaxial strut was introduced for thermoelectric generator applications. The increment of the data communication between machine to machine, machine to human and human to human leads the requirement of collecting data from any kinds of sensors. One of the most important sensor is pressure sensor which can give information of blood pressure, heat beating rate or something. And the electric energy source is required to these kinds of electric devices, and the energy source is also needed to be flexible for the wearable electric devices. Recently, wearable thermoelectric generator based on organic materials are reported and the wearable TEG can generate several microwatt energies. However, to apply these wearable TEG, any kind of electric device should be assembled together with TEG. We introduced coaxial structure for thermoelectric generator. It is found that shell structure of SEBS give the mechanical strength and recovery properties to the foam and PEDOT:PSS is well-known thermoelectric polymer which have moderate thermopower and high electrical conductivity and used to the thermoelectric foam structure for thermoelectric generator. This SPM was assembled to the wearable thermoelectric generator and could generate 338 nW from the forearm.
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dc.description.tableofcontentsChapter 1 Introduction 1

1.1 Block Copolymer Self-assembly for Nanolithography 2

1.2. 2 Dimensional Materials for Thermoelectrics and Size Effect in Low Dimensional Materials 4

1.3. Motivation 8

1.4. References 10

Chapter 2 Control of Block Copolymer Nano Domains for Nanolithography 20

2.1. Introduction 21

2.2. Experimental 24

2.3. Results and Discussion 27

2.4. Conclusion 34

2.5. References 35

Chapter 3 Significantly reduced thermal conductivity and enhanced thermoelectric properties of single- and bi-layer graphene nanomeshes with sub-10 nm neck-width 57

3.1. Introduction 58

3.2. Experimental 62

3.3. Results and Discussion 75

3.4. Conclusion 88

3.5. References 89

Chapter 4 Van der Waals Heterostructure of Graphene Nanostructure and Molybdenum Disulfide for Superior Thermoelectric Materials 113

4.1. Introduction 114

4.2. Experimental 117

4.3. Results and Discussion 121

4.4. Conclusion 124

4.5. References 125

Chapter 5 Coaxial Struts and Microfractured Structures of Compressible Thermoelectric Foams for Self-powered Pressure Sensors 143

5.1. Introduction 144

5.2. Experimental 147

5.3. Results and Discussion 152

5.4. Conclusion 161

5.5. Refences 163

Abstract in Korean 186
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dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subject.ddc660.6-
dc.titleNanopatterned 2D Materials using Block Copolymer Nano-Lithography for Superior Thermoelectrics-
dc.title.alternative블록공중합체의 나노 구조 제어를 통하여 나노 패턴된 이차원 물질의 열전 성능 극대화에 대한 연구-
dc.typeThesis-
dc.contributor.AlternativeAuthorJinwoo Oh-
dc.description.degreeDoctor-
dc.contributor.affiliation공과대학 화학생물공학부-
dc.date.awarded2018-08-
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