Carbon-based structures have grabbed much attention in the last decades. Moreover, they have been spread in many technological areas like nanoelectronics, high strength materials, laser technology and optical materials. Diamond and graphite are well known since ancient times as all carbon materials with a variety of applications. However, the missing third carbon allotrope is the one-dimension sp-carbon linear chain (carbyne), where, due to stability issues, its existence is questionable. Nonetheless, structures based on sp-carbon chains have been synthesized and investigated. While the theoretical work in the field of sp-carbon atomic chains is at advanced stages, many experimental investigations are not present yet. Sp-carbon atomic chains-based structures are very appealing due to their properties of tunability and the possibility that they can be integrated into different systems opening multiple windows for technological applications. One of the most interesting properties predicted for the chains is the electrical conductivity, very few works have been done in this area up to now due to the difficulty of the electrical characterization process of these systems. Indeed, the main motivation of this work is to investigate the electrical properties of sp-carbon chain-based molecules. In this work, four molecules were characterized and insightful information about their electrical properties was obtained. The characterization was done on the molecules in their crystalline form. The crystalline films of the molecules were obtained using drop casting and spin coating techniques and after, the electrical conductivity of these films was measured. Moreover, field effect transistors were successfully fabricated and tested using two of these molecules and data about the charge mobility of these molecules was revealed. Indeed, organic field effect transistors’ field is a widely growing field, so it offers options for cheap and flexible electronics and it is an important tool for investigating the charge transport in organic semiconductors where their transport mechanisms are still ambiguous. Furthermore, Raman characterization of the molecules was done and it was used for stability checking. The vibrational properties of the molecules revealed by Raman helped in the interpretation of the results. Moreover, UV-Vis spectroscopy was used to investigate the electronic properties of the molecules which again helped in the interpretation of the results. Finally, optical microscope along with scanning electron microscope images were used for characterizing the formed crystals for a complete characterization picture. This work provides a new way of investigating the conduction properties of sp-carbon chains. It introduces a new class of materials to the family of organic semiconductors which shall help in a better understanding of their transport mechanisms. Finally, it opens a new area for improving the field of field effect transistors.
Le strutture a base di carbonio hanno attirato molta attenzione negli ultimi decenni. Infatti, si sono diffuse in molte aree tecnologiche come la nanoelettronica, i materiali ad alta resistenza, la tecnologia laser e i materiali per ottica. Diamante e grafite sono noti fin dall'antichità come materiali composti totalmente di carbonio con una varietà di applicazioni. Tuttavia, la terza forma allotropica mancante del carbonio è la catena lineare carbonio-sp a una dimensione (carbyne), per cui, a causa di problemi di stabilità, la sua esistenza rimane in qualche modo discutibile. Nonostante ciò, le strutture basate su catene di carbonio-sp sono state sintetizzate e investigate. Mentre il lavoro teorico sul campo delle catene atomiche carbonio-sp è in fase avanzata, non sono invece presenti numerevoli indagini sperimentali. Le strutture basate su catene atomiche carbonio-sp sono molto allettanti grazie alla loro flessibilità sulle proprietà e alla loro possibilità di essere integrate con diversi sistemi aprendo ulteriori vie per applicazioni tecnologiche. Una delle proprietà più interessanti previste per le catene carbonio-sp è la conduttività elettrica, ma in questa area sono stati eseguiti pochissimi lavori finora a causa della difficoltà del processo di caratterizzazione elettrica di questi sistemi. Difatti, la motivazione principale di questo lavoro è l’indagine delle proprietà elettriche delle catene di carbonio-sp. In questo lavoro, sono state caratterizzate quattro diverse molecole da cui sono state ottenute informazioni importanti sulle loro proprietà elettriche. La caratterizzazione è stata effettuata sulle molecole nella loro forma cristallina. I film cristallini delle molecole sono stati ottenuti utilizzando tecniche di “drop casting” e “spin coating” e successivamente la conducibilità elettrica di questi film è stata misurata. Inoltre, transistor a effetto di campo sono stati fabbricati e testati con successo, utilizzando due di queste molecule, da cui sono state rivelate informazioni sulla mobilità di carica di queste molecole. Infatti, il campo dei transistor organici ad effetto di campo è un settore in grande espansione in quanto offre possibilità di una elettronica economica e flessibile ed è uno strumento importante per lo studio del trasporto di carica nei semiconduttori organici dove i loro meccanismi di trasporto sono ancora ambigui. Inoltre, la spettroscopia Raman delle molecole è stata eseguita per valutare la stabilità. Le proprietà vibrazionali delle molecole rivelate da Raman hanno aiutato nell'interpretazione dei risultati. Inoltre, la spettroscopia UV-Vis è stata utilizzata per studiare le proprietà elettroniche delle molecole che hanno anche’esse aiutato nell'interpretazione dei risultati. Infine, il microscopio ottico insieme alle immagini del microscopio elettronico a scansione sono stati utilizzati per caratterizzare i cristalli formati per avere un quadro complete di caratterizzazione. Questo lavoro fornisce un nuovo modo di studiare le proprietà di conduzione delle catene di carbonio sp. Introduce una nuova classe di materiali alla famiglia dei semiconduttori organici che contribuirà ad una migliore comprensione dei loro meccanismi di trasporto. Infine, apre una nuova area per il miglioramento nel campo dei transistor a effetto di campo.
Electrical transport properties investigation of Sp-carbon atomic chains-based molecular crystals
SOLIMAN, MOHAMED TAREK SAID ZOELFAKAR
2017/2018
Abstract
Carbon-based structures have grabbed much attention in the last decades. Moreover, they have been spread in many technological areas like nanoelectronics, high strength materials, laser technology and optical materials. Diamond and graphite are well known since ancient times as all carbon materials with a variety of applications. However, the missing third carbon allotrope is the one-dimension sp-carbon linear chain (carbyne), where, due to stability issues, its existence is questionable. Nonetheless, structures based on sp-carbon chains have been synthesized and investigated. While the theoretical work in the field of sp-carbon atomic chains is at advanced stages, many experimental investigations are not present yet. Sp-carbon atomic chains-based structures are very appealing due to their properties of tunability and the possibility that they can be integrated into different systems opening multiple windows for technological applications. One of the most interesting properties predicted for the chains is the electrical conductivity, very few works have been done in this area up to now due to the difficulty of the electrical characterization process of these systems. Indeed, the main motivation of this work is to investigate the electrical properties of sp-carbon chain-based molecules. In this work, four molecules were characterized and insightful information about their electrical properties was obtained. The characterization was done on the molecules in their crystalline form. The crystalline films of the molecules were obtained using drop casting and spin coating techniques and after, the electrical conductivity of these films was measured. Moreover, field effect transistors were successfully fabricated and tested using two of these molecules and data about the charge mobility of these molecules was revealed. Indeed, organic field effect transistors’ field is a widely growing field, so it offers options for cheap and flexible electronics and it is an important tool for investigating the charge transport in organic semiconductors where their transport mechanisms are still ambiguous. Furthermore, Raman characterization of the molecules was done and it was used for stability checking. The vibrational properties of the molecules revealed by Raman helped in the interpretation of the results. Moreover, UV-Vis spectroscopy was used to investigate the electronic properties of the molecules which again helped in the interpretation of the results. Finally, optical microscope along with scanning electron microscope images were used for characterizing the formed crystals for a complete characterization picture. This work provides a new way of investigating the conduction properties of sp-carbon chains. It introduces a new class of materials to the family of organic semiconductors which shall help in a better understanding of their transport mechanisms. Finally, it opens a new area for improving the field of field effect transistors.| File | Dimensione | Formato | |
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Thesis Mohamed Soliman.pdf
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https://hdl.handle.net/10589/147221