Synthesis And Growth Mechanism Of Carbon Nanotubes On Different Substrates Through CVD Method

CNTs, due to their extraordinary electronic properties, have a wide range ofapplications in the manufacturing of electronic devices. Among the various synthesismethods of CNTs, chemical vapor deposition (CVD) is a most convenient one thatcan produce large-scale CNT arrays during a single process. There is a"selective-growth" phenomenon of CNTs when CVD processes are applied, and it isgenerally acknowledged that CNTs are inclined to grow on transition metals such asFe, Co, Ni and substrates like SiO2, while Si and Au do not support this type ofgrowth. This feature of CNT growth is further harnessed to fabricate 1-D, 2-D, and3-D architectures of CNTs on patterned substrates. As a result, we choose the growthof CNTs on different substrates, the experimental control, and the growth mechanismas the topic of this thesis.Firstly, we investigated the fabrication of sub-micron circular patterns ofα -Fe₂O₃ nanoparticles and linear patterns of γ-Fe₂O₃ nanoparticles on SiO₂substrates, and discussed the influence of experimental parameters on themorphologies and structures of the products. After that, we studied the growthof CNTs on pristine Si substates, as well as on Si substrates patterned with Feand Au, respectively. On Si substrates with Fe patterns, we observed acondition-oriented, two-regime growth of CNTs and disordered carbonnanowires;on pristine Si substrates and Si substrates with Au patterns whichwere presumed as non-supportive for CNTs growth, we successfully gotvertically aligned arrays of CNTs by controlling the reaction kinetics.It was also shown in our study that the changes in the reaction kinetics onSi and Au/Si substrates, however, did not eliminate the selectivity of CNTgrowth. As Si and Au have different reasons for their non-supportivebehaviors of CNT growth, there existed a discrepancy in the purpose of thekinetic control in our study. For the pristine Si substrates, it is most importantto suppress the rapid reaction between catalyst particles and the substratesurface, while for Si substrates with Au patterns, the trick lies in utilizing andcontrolling the correlationship between CNT growth and the vaporization ofAu film.