UPSI Digital Repository (UDRep)
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UPSI Digital Repository (UDRep)
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| Abstract : Universiti Pendidikan Sultan Idris |
| Carbon-based advanced nanomaterials are important for the devices of next generation, such as in field effect transistors, sensors, nanoelectronics, nanocomposites and flexible displays. In recent years, one-dimensional carbon nanotubes (CNTs) and two-dimensional graphene have become new members of the carbon family. They are ideal model materials for low-dimensional sciences, and are regarded as the key materials for future nanoscience and nanotechnology. For the device applications, their controllable synthesis and position control should be indispensable. In this thesis, these issues are challenged by dynamically observing their formation process in atomic dimension inside transmission electron microscopy (TEM). For the in-situ TEM dynamical observation, the sample preparation is a key factor. Firstly, platinum (Pt)-, palladium (Pd)- and cobalt (Co)-included amorphous carbon nanofibers (CNFs) as well as pristine (pure) CNFs were fabricated on the edges of graphite foil by argon (Ar+) ion irradiation with and without a supply of those metals at room temperature. Also, the controllable synthesis of copper-carbon nanoneedles (CuCNNs) with higher Cu concentration than C directly on an edge of Cu foil by Ar" ion irradiation with a supply of C during ion irradiation was achieved. They were featured by the amorphous carbon structure with the inclusion of metal nanoparticles. For a comparison, Cu-coated pristine CNFs were also prepared. For those samples, dynamic TEM observation was performed by in-situ current-voltage (I-V) measurement and/or direct heating in TEM.In-situ 1-V measurement of both Cu-CNNs and Cu coated CNFs in TEM revealed for the first time that current increased gradually at the beginning and suddenly steeply increased with applied voltage due to the transformation from amorphous carbon to graphene catalyzed by Cu. After the formation of graphene, current density as high as 106 A'crrr', which is comparable to that of Cu film in normal interconnect application was achieved. Graphene formation was due to the Joule heating induced by the electron current flow. Compared with Cu-coated CNFs, the formation temperature of graphene as low as 1073 K was realized for Cu-CNNs, thanks to the reduction in melting point induced by the size effect ofCu nanoparticles dispersed in the Cu-CNNs. In-situ I-V measurement ofPd-included CNFs in TEM resulted in the formation of graphene which involves the thermomigration starting from the middle part of the structure. This thermomigration also was due to Joule heating induced by the electron current flow. It also proved that Pd possessed a good ohmic contact with carbon materials. This implies that it can be replaceable to gold as an electrode for carbon interconnection application. Different from the Pd and Cu cases, the in-situ 1-V measurement of Co-included CNF showed that Co nanoparticle in CNF migrated through electromigration phenomenon and resulted in the formation of Co-capped CNTs due to the current induced Joule heating. This implies that movement of Co particle is controllable, thus being advantageous to apply it to fabricate a probe for magnetic force microscopy (MFM), because CNTs probe with a magnetic particle on the tip is known to be ideal for the better performance of MFM. v In-situ I-V measurement of Pt-included CNF in TEM led to the formation of a multilayer CNTs through electromigration behavior ofPt nanoparticles. The driving force for the transformation was current induced Joule heating. The movement of Pt nanoparticles were controllable and by using this controllable movement, the connection of two CNTs was achieved. So, the application of this controllable migration of Pt will open a door for nanosoldering of carbon nanostructure. Thus, this thesis demonstrated the potential of engineering the controllable formation of graphene and CNTs as well as position control by solid phase reaction for various future device applications. |
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