Kumar, Sandeep (2022)
Nanocarbon Devices and Sensors.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00021384
Dissertation, Erstveröffentlichung, Verlagsversion
Kurzbeschreibung (Abstract)
Nanocarbon materials have the potential to substitute the silicon in devices that are needed to further improve in terms of scalability, speed of operation, and performance. Therefore, carbon nanotubes and graphene - allotropes with outstanding properties have been intensively explored over the years. This thesis contributes to the synthesis of nanocarbon materials and its use as sensing and transistor material by focusing on the topics: hysteresis in carbon nanotube field-effect transistors, selective molecule sensing with graphene field-effect transistors, and sensing applications in nanocrystalline graphene. Hysteresis in carbon nanotube transistors has limited its utility in large-scale device implementation. The issue of hysteresis in such device structures is addressed. A hysteresis-free device operation is achieved by packaging the carbon nanotube field-effect transistors between hexagonal boron nitride and a hydrophobic polymer Teflon. The findings indicate that hysteresis is eradicated only if the metal-carbon nanotube contacts along with the tubes are completely encapsulated with Teflon. The time dependence of reducing hysteresis for encapsulated devices indicates out-diffusion of water molecules adsorbed at the metal-nanotube contacts. Graphene field-effect transistors suffer the issue of selectivity applications. A novel sensor based on graphene field-effect transistor and surface-mounted metal-organic frameworks is demonstrated. The sensor shows sensitivity and selectivity to ethanol molecules by the shift in Dirac voltage of graphene and is insensitive to other alcohols like methanol and isopropanol, and molecules like CO2, H2O, H2. The device performance shows a detection limit of 100 ppm levels. This class of sensors is tailorable and opens up a completely new range of sensors. Nanocrystalline graphene is an interesting material for several sensing applications like strain sensing, moisture sensing, gas sensing, etc. In order to be investigated as strain sensor, thin films should be either grown or transferred on flexible substrates. This motivated the study of the low-temperature synthesis (600°C) process using a metal capping layer over a carbon source. Raman spectroscopy is used to characterize the grown films. The results indicate this technique promising for a low-temperature NCG synthesis. Next, thin-film transfer technique on flexible substrate is studied. The quality of transferred films on different substrates is confirmed by atomic force microscopy. Next, influence of temperature on conductivity of thin films of NCG is investigated. Piezoresistive property of nanocrystalline graphene is explored based on changes in sheet resistance of the film and Raman spectroscopy. Finally, a potential application is demonstrated where a top (ionic liquid) gate field effect configuration of NCG works as a moisture sensor.
Typ des Eintrags: | Dissertation | ||||
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Erschienen: | 2022 | ||||
Autor(en): | Kumar, Sandeep | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | Nanocarbon Devices and Sensors | ||||
Sprache: | Englisch | ||||
Referenten: | Krupke, Prof. Dr. Ralph ; Hofmann, Prof. Dr. Jan Philipp | ||||
Publikationsjahr: | 2022 | ||||
Ort: | Darmstadt | ||||
Kollation: | 153 Seiten | ||||
Datum der mündlichen Prüfung: | 8 Dezember 2021 | ||||
DOI: | 10.26083/tuprints-00021384 | ||||
URL / URN: | https://tuprints.ulb.tu-darmstadt.de/21384 | ||||
Kurzbeschreibung (Abstract): | Nanocarbon materials have the potential to substitute the silicon in devices that are needed to further improve in terms of scalability, speed of operation, and performance. Therefore, carbon nanotubes and graphene - allotropes with outstanding properties have been intensively explored over the years. This thesis contributes to the synthesis of nanocarbon materials and its use as sensing and transistor material by focusing on the topics: hysteresis in carbon nanotube field-effect transistors, selective molecule sensing with graphene field-effect transistors, and sensing applications in nanocrystalline graphene. Hysteresis in carbon nanotube transistors has limited its utility in large-scale device implementation. The issue of hysteresis in such device structures is addressed. A hysteresis-free device operation is achieved by packaging the carbon nanotube field-effect transistors between hexagonal boron nitride and a hydrophobic polymer Teflon. The findings indicate that hysteresis is eradicated only if the metal-carbon nanotube contacts along with the tubes are completely encapsulated with Teflon. The time dependence of reducing hysteresis for encapsulated devices indicates out-diffusion of water molecules adsorbed at the metal-nanotube contacts. Graphene field-effect transistors suffer the issue of selectivity applications. A novel sensor based on graphene field-effect transistor and surface-mounted metal-organic frameworks is demonstrated. The sensor shows sensitivity and selectivity to ethanol molecules by the shift in Dirac voltage of graphene and is insensitive to other alcohols like methanol and isopropanol, and molecules like CO2, H2O, H2. The device performance shows a detection limit of 100 ppm levels. This class of sensors is tailorable and opens up a completely new range of sensors. Nanocrystalline graphene is an interesting material for several sensing applications like strain sensing, moisture sensing, gas sensing, etc. In order to be investigated as strain sensor, thin films should be either grown or transferred on flexible substrates. This motivated the study of the low-temperature synthesis (600°C) process using a metal capping layer over a carbon source. Raman spectroscopy is used to characterize the grown films. The results indicate this technique promising for a low-temperature NCG synthesis. Next, thin-film transfer technique on flexible substrate is studied. The quality of transferred films on different substrates is confirmed by atomic force microscopy. Next, influence of temperature on conductivity of thin films of NCG is investigated. Piezoresistive property of nanocrystalline graphene is explored based on changes in sheet resistance of the film and Raman spectroscopy. Finally, a potential application is demonstrated where a top (ionic liquid) gate field effect configuration of NCG works as a moisture sensor. |
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Alternatives oder übersetztes Abstract: |
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Status: | Verlagsversion | ||||
URN: | urn:nbn:de:tuda-tuprints-213845 | ||||
Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 530 Physik 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften und Maschinenbau |
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Fachbereich(e)/-gebiet(e): | 11 Fachbereich Material- und Geowissenschaften 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Fachgebiet Molekulare Nanostrukturen |
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Hinterlegungsdatum: | 19 Mai 2022 12:04 | ||||
Letzte Änderung: | 15 Aug 2022 12:04 | ||||
PPN: | 49553367X | ||||
Referenten: | Krupke, Prof. Dr. Ralph ; Hofmann, Prof. Dr. Jan Philipp | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 8 Dezember 2021 | ||||
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