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Investigation of electrical and mechanical characteristics of the two-dimensional nanomaterials/polymer systems
- Author(s)
- 채관병
- Advisor
- 박지용
- Department
- 일반대학원 에너지시스템학과
- Publisher
- The Graduate School, Ajou University
- Publication Year
- 2022-02
- Language
- eng
- Keyword
- 2D nanomaterials; crack; polymer system
- Alternative Abstract
- In this paper, we discussed the mechanical properties of two-dimensional nanomaterials and polymer substrate systems and the electrical properties of polymer dielectric materials. Graphene and Molybdenum disulfide (MoS2) were synthesized by Chemical Vapor Deposition (CVD) method, and the CVD parameters for synthesizing into a single layer were optimized. The synthesized two-dimensional nanomaterial was investigated by Optical Microscopy (OM), Atomic Force Microscopy (AFM), and Raman spectroscopy. In addition, in order to measure the electrical properties of the synthesized two-dimensional nanomaterial, it was fabricated as a FET device, and electron mobility of about 1000 cm2/Vs for graphene and about 2 cm2/Vs for MoS2 was measured using a probe station. First, the two-dimensional nanomaterial synthesized by CVD is transferred onto a poly (methyl methacrylate) (PMMA) substrate, and then the PMMA is swollen using methanol or ethanol. We found that strain caused by the expansion of the PMMA layer caused cracks on the surface of the transferred 2D nanomaterial. In the case of graphene, a rectangular pattern was used, and as the length of the width increased, we confirmed that more cracks were generated in the vertical direction (the long direction of the rectangle). In the case of MoS2, cracks were mainly generated in the zig-zag direction where bonding was relatively weak because each flake grew as single crystalline, and we confirmed that there is a minimum area for accumulating the strain required for crack formation. In addition, by introducing fracture mechanics, we confirmed that the difference in elastic modulus in the laminated structure of heterogeneous materials can accelerate crack formation. And when the two-dimensional nanomaterial/PMMA device was immersed in alcohol, through in-situ IV measurement, we verified that the crack formation occurred simultaneously with the swelling. In addition, the crack pattern according to the change of the surface state of the two-dimensional nanomaterial was observed, and the possibility of new nanostructure creation or applications such as sensors and fuses was suggested through re-transfer and PDMS imprint. Next, we describe the electrical properties of the ion gel synthesized from poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]) according to the mass ratio. Characteristics were measured and applied as dielectric material to flexible graphene FET. We developed a mass ratio of ion gel that best maintains electric double layer capacitance (EDLC) properties of ionic liquid without losing flexibility through capacitance and impedance measurement and compared the measured and calculated results by deriving an equivalent circuit of the device. In addition, we applied the graphene FET fabricated on PET substrate as a gate dielectric material to prove that it works without losing the electrical properties of graphene even when strain is applied.
- Fulltext
- Appears in Collections:
- Graduate School of Ajou University > Department of Energy Systems > 4. Theses(Ph.D)
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