Publications

Detailed Information

Electrical Properties of Sorted Carbon Nanotube Networks and Their Application for Gas Sensors : 분리된 탄소나노튜브의 전기적 성질과 이를 이용한 가스센서 개발에 관한 연구

DC Field Value Language
dc.contributor.advisor홍승훈-
dc.contributor.author김정수-
dc.date.accessioned2017-10-27T17:10:38Z-
dc.date.available2017-10-27T17:10:38Z-
dc.date.issued2017-08-
dc.identifier.other000000146099-
dc.identifier.urihttps://hdl.handle.net/10371/137128-
dc.description학위논문 (박사)-- 서울대학교 대학원 자연과학대학 물리·천문학부, 2017. 8. 홍승훈.-
dc.description.abstractCarbon nanotube (CNT) is considered as a promising material for future electronics due to its excellent electrical properties such as a high current density, a high on-off ratio, a high mobility and a low subthershold swing. However, practical applications for CNT-based devices are hindered by complex and time-consuming fabrication processes. For example, the chirality of an as-grown CNT is determined randomly, so As-grown CNTs has the problem that they consist of semiconducting CNTs (s-CNTs) and metallic CNTs (m-CNTs). The electrical properties of s-CNTs and m-CNTs are opposite to each other. Thus, it is difficult to expect a good performance when a device is made using as-grown CNTs. To solve the problem, recently, a density gradient ultracentrifugation (DGU) method was developed to sort as-grown CNTs into m-CNTs and s-CNTs. However, practical applications using sorted-CNTs are still being studied because of the complexity of the fabrication process.
In this dissertation, I and co-works have explored electrical properties of sorted CNTs. In addition, we will propose a new strategy for the fabrication of CNT-based gas sensors as a practical application.
First, we will discuss pristine semiconducting carbon nanotube network-based devices exhibiting intrinsic characteristics. Conventional sorted CNT-based devices have disadvantages that surfactants or CNT bundles are exist in their channels. These surfactants and CNT bundles lower the performance of the performance of CNT-based devices, but it is extremely difficult to remove both surfactants and CNT bundles simultaneously. Here, the solutions of pristine s-CNT without bundles or organic impurities were prepared in 1, 2-dichlobenzene solutions via filtration and centrifugation processes. A FET device based on a pristine s-CNT network exhibited a rather large on−off ratio up to over ∼106 and a subthreshold swing as small as ∼490 mV/dec, which are comparable to those of devices based on a single s-CNT.
Next, we will discuss the scanning noise microscopy method for the measurement of the noise characteristics of sorted carbon nanotube networks. Here, we measured the current maps and the electrical noise power spectral density (PSD) maps of a s-CNT network and a m-CNT networks via a modified conducting AFM system. By analysing the current maps and the PSD maps, we investigated the noise source activities of sorted CNTs. We found that the noise activities of sorted CNT networks were just depending on the diameter of each CNT and the density of CNT network. Also, in the case of a s-CNT network, we found that noise activities were high at crossed-CNT junctions.
Lastly, a dye-functionalized sol-gel matrix on a s-CNT network for dual-mode sensing will be discussed. Here, the CNT-dye hybrid gas sensors were fabricated by functionalizing dye molecules on top of s-CNT networks via a sol-gel method. The CNT-dye hybrid gas sensors could selectively detected SO2, NH3 and Cl2 gases. The sensitivity of the gas sensor exhibited more than 50 % by the exposure to the gas species with its concentration even under its permissible exposure limit. Also, we could refresh used gas sensors simply by exposing it to fresh N2 gas without any heat treatment.
These works could provide an important insight regarding the electrical properties of sorted CNTs and their possibility for practical applications.
-
dc.description.tableofcontentsChapter 1. Introduction 1
1.1 Carbon Nanotubes 1
1.2 Sorted Carbon Nanotubes 5
References 8
Chapter 2. Pristine Semiconducting Carbon Nanotube Network Exhibiting Intrinsic Characteristics 10
2.1 Introduction 10
2.2 CNT Schottky Barrier Transistor 12
2.3 Surface Programmed Assembly Method 14
2.4 Experimental Procedure 16
2.4.1 Preparation of Pristine s-CNT Solution without Surfactant or CNT Bundles 16
2.4.2 Fabrication of Pristine s-CNT-FET 19
2.5 Result and Discussion 21
2.5.1 Component Analysis of Pristine s-CNT Solution 21
2.5.2 AFM and optical images of pristine s-CNT-based FETs 23
2.5.3 Electrical characteristics of pristine s-CNT network-based FETs 26
2.5.4 Scaling Behavior of s-CNT Network-based FETs 31
2.6 Summary 35
References 37
Chapter 3. Scanning Noise Microscopy on Sorted CNT Network 41
3.1 Introduction 41
3.2 Low-Frequency Noise 43
3.3 1/f Noises in Nanomaterials 45
3.4 Calculation of Conductivity Map on 2-D Materials 48
3.5 Calculation of a Noise Source Density Map on 2-D Materials 52
3.6 Experimental Setup for SNM 58
3.6.1 CNT Network Sample Preperation 58
3.6.2 Noise Measurement 59
3.7 Result and Discussion 61
3.7.1 Noise Source imaging of a Metallic Carbon Nanotube Network 61
3.7.2 Noise Source imaging of a Semiconducting Carbon Nanotube Network 67
3.7.3 Noise Source imaging of a Cross-patterned Carbon Nanotube Network 72
3.8 Summary 75
References 77
Chapter 4. CNT-dye Hybrid Structure for Gas Sensor Application 81
4.1 Introduction 81
4.2 Fabrication Process of a CNT-dye hybrid Gas Sensor and Its Sensing Mechanism 83
4.2.1 Synthetic Method for Sol-Gel Metrix 83
4.2.2 Fabrication Process of a CNT-dye Hybrid Gas Sensor 84
4.2.3 Sensing Mechanism 85
4.3 Result and Discussion 86
4.3.1 Basic Properties of Gas Sensor 86
4.3.2 Selective and Refreshable Gas Sensing with a Humidity Calibration 88
4.3.3 Tube-Shape Gas Sensors based on Folded CNT Sensors 95
4.5 Summary 97
References 98
Chapter 5. Conclusion 101
Chapter 6. Abstract in Korean 초록 103
-
dc.formatapplication/pdf-
dc.format.extent3088240 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectcarbon nanotube-
dc.subjecttransisot-
dc.subjectcentrifugation-
dc.subjectatomic force microscopy-
dc.subjectlow-frequency noise-
dc.subjectnoise imaging-
dc.subjectcolorimetric sensor-
dc.subjectgas sensor-
dc.subject.ddc523.01-
dc.titleElectrical Properties of Sorted Carbon Nanotube Networks and Their Application for Gas Sensors-
dc.title.alternative분리된 탄소나노튜브의 전기적 성질과 이를 이용한 가스센서 개발에 관한 연구-
dc.typeThesis-
dc.description.degreeDoctor-
dc.contributor.affiliation자연과학대학 물리·천문학부-
dc.date.awarded2017-08-
Appears in Collections:
Files in This Item:

Altmetrics

Item View & Download Count

  • mendeley

Items in S-Space are protected by copyright, with all rights reserved, unless otherwise indicated.

Share