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Monocrystalline graphene is desirable for practical applications since the large-scale polycrystalline graphene grown by chemical vapor deposition is limited in terms of performance. The transfer of graphene film from the metallic growth substrate to a host substrate, which is generally required for practical applications, can further damage the graphene by inducing strain, defects and wrinkles or by leaving contamination such as polymer residues. In this work, we have investigated the influence of the transfer process on the monocrystalline graphene in terms of quality, morphology and electrical properties by analyzing the data obtained from optical microscopy, scanning electron microscopy, Raman spectroscopy and electrical characterizations. The influence of copper oxidation on graphene prior to the transfer is also discussed. Our results show that the "Bubble-free" electrochemical delamination transfer is an easy and fast transfer technique suitable for transferring large single crystals graphene with an almost defect free surface. Moreover, Raman spectroscopy investigation reveals that the Cu surface oxidation modify the strain of the graphene film. We have observed that graphene laying on unoxidized Cu is submitted to a biaxial strain in compression, while graphene on Cu oxide is submitted to a biaxial strain in tension. However, after graphene was transferred to a host substrate, these strain effects disappeared leaving a homogeneous graphene on the substrate. Finally, we used the transferred single crystal graphene on silicon oxide substrate to fabricate transmission line method (TLM) devices. These electrical measurements show low contact resistance ~150 Ω.µm, which confirms the homogeneity and good quality of transferred graphene. Therefore, electrochemical delamination process can be used to transfer large single crystal graphene in a fast and reliable way.

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Carbon nanotubes (CNTs) are considered as one of the most intensively explored nanostructured materials and have been widely used as a platform material for metal and semiconductor nanoparticles (NPs) due to their large and chemically active surface area. Several approaches have been described in the literature to immobilize NPs on the surface of CNTs. This report reviews the recent developments in this area by exploring the various techniques where nanotubes can be functionalized with NPs to improve the optical, mechanical, thermal, medical, electrical, and magnetic applications of CNTs.

1 Introduction||2 Methodology||3 Tuning the electrical property of single-layer graphene nanoribbon by adsorption of planar molecular nanoparticles||4 Fabrication of turbostratic multi-layer graphene nanoribbon field effect transistor and investigating the electrical property with the adsorption of HAT-CN666||5 Fabrication of X- and Y-type graphene nanoribbon cross junction and study the electrical transport property||6 Conclusion, Graphene nanoribbon （GNR） is a narrow strip of carbon atoms which has exceptional properties and are being exploited for various applications, such as in semiconductor electronics, solar cells, and sensors. However, the realization of GNR based devices still needs an extensive research to achieve the commercial specifications. This research is mainly emphasized on the synthesis of high-quality GNR from double-walled carbon nanotubes （DWNTs） and fabrication of field effect transistor （FET） devices. Moreover, the electrical transport properties were also investigated for single-layer GNR （sGNR）, multi-layer GNR with and without adsorption of molecular nanoparticles. The electrical transport properties of GNR device was tuned to semiconducting with the adsorption of molecular nanoparticles. This study demonstrates a simple and fast approach to band gap formation in sGNR using Hexaazatriphenylenehexacarbonitrile （HAT-CN6）. In this process, sGNRs were synthesized by unzipping of DWNTs followed by casting the solution of HAT-CN6. HAT-CN6 on GNR forms self-assembled nanoparticle and the adsorption of nanoparticles was confirmed by AFM observation. Further, the electric property of pristine sGNR device and the device with HAT-CN6 were measured using point-contact current imaging （PCI-） AFM and also with the FET device. Thus, the adsorbed nanoparticles on sGNR forms the electron trapping sites which result in a necklike structure of sGNR near the adsorbed region of the molecular nanoparticle. The neck region working similar to narrow width GNR （< 10 nm） allows the charge carriers passing through. Such a narrow sGNR has lateral confinement of charge carrier around the neck region hence the device turns to semiconducting. The activation energy of pristine sGNR and the sGNR with HAT-CN6 were calculated by the results of temperature change measurement as about 1.5 meV and 52 meV, respectively. The pristine sGNR has very low activation energy as compared to the device with HAT-CN6. Thus, the device with HAT-CN6 has a large transition from semimetallic to semiconducting property. The device could have various possible application in future electronics industry due to its semiconducting property. Moreover, the study also explains the fabrication of multi-layer GNR （mGNR） field effect transistor （FET） and control of its electrical property with the adsorption of the flat molecular nanoparticle. The stacked mGNR device shows the similar performance to the sGNR device due to lower inter layer coupling. Inter layer interaction was supposed to be lower since the turbostratic stacking of GNR was formed with CVD growth process. Next, HAT-CN6 were casted on the mGNR device to alter the electronic property of GNR. Thus, the adsorbed nanoparticles form the charge carrier trapping sites on mGNR and the channel width was narrowed due to the nanoparticles on GNR. Hence, the charge carriers are confined in a narrow channel and the device is in a transition state from semimetallic to semiconducting, which is similar to narrow width GNR. The on/off ratio and mobility of mGNR-FET device was also improved with the adsorption of the nanoparticle. The fabricated mGNR-FET device has wide area of semiconductor electronics applications in the semiconductor industry. Furthermore, X- and Y-type junctions were also fabricated using GNRs obtained by unzipping of DWNTs. The junction of the synthesized GNR shows semiconducting property whereas the other part shows the semimetallic property. The semiconducting property at the junction was supposed to be due to change in lattice orientation at the junction of two GNRs. Such a junction can have great interest for the device and wiring application in the semiconductor industry. The semiconducting property in the several X-type junctions of wide GNRs （greater than 10 nm） was investigated., 九州工業大学博士学位論文 学位記番号：生工博甲第295号 学位授与年月日：平成29年6月30日, 平成29年度