Nanophotonics of vertically aligned carbon nanotubes: Two-dimensional photonic crystals and optical dipole antennas

Carbon nanotubes (CNTs) and related nanostructures represent a novel class of condensed matters with intriguing properties due to their unique atomic structures and nanoscale morphologies. It is of particular interest to examine the interaction behavior and mechanism between the free electron gas within carbon nanotubes and the external electromagnetic wave, which may greatly facilitate the understanding of the physics of nanophotonics at the fundamental level. This dissertation is committed to investigate the optical responses of arrays of vertically aligned CNTs in different configurations, based on their fabrication by Plasma-Enhanced Chemical Vapor Deposition (PECVD) and other techniques involved therein. The mechanisms of the photonic results are categorized into inter-CNT and intra-CNT contributions through data analysis on periodic and random CNT arrays, which then give rise to practical applications in photonic crystals and optical antennas.; The growth and fabrication procedure of vertically aligned CNTs with optimized morphology and well-defined arrangement is first elaborated in this dissertation, owing to the tremendous difficulties encountered and efforts paid during the sample fabrication and optimization process, and the dominant effect of sample quality on the final results at the optical characterization stage. To fabricate periodic CNT arrays, a microsphere self-assembly technique is first adopted for catalyst patterning and a parametric study is carried out systematically for CNT growth by PECVD method. For random CNT arrays, the growth conditions are also modified so that small diameter CNTs can be grown and an IC industry-compatible procedure can be developed for practical application purposes.; The inter-scatterer optical responses are studied by using hexagonal lattices of vertically aligned CNTs with various lattice constants and CNT morphologies. The diffraction patterns of theses CNT arrays are recorded and compared to theoretical calculations based on Bragg diffraction principles for two-dimensional photonic crystals where good consistencies are obtained.; The intra-scatterer optical responses are investigated using random CNT arrays with various CNT spacing and lengths. The reflection spectra revealed optical antenna effects of individual vertically aligned CNTs including polarization effect, length-matching effect and multilobe radiation pattern. The results indicate that photocurrents are generated on the CNTs upon illumination. Challenges are identified and potential solutions are proposed to utilize CNT optical antennas for optoelectronic applications.