Carbon nanotubes have several extreme properties ranging from their mechanical strength, thermal and electronic conductivity, to very unusual electronic structures. Their unusual electronic structures inherited from graphene, provides a multitude of electronic properties for the different nanotube species. The nanoscale size tubes is responsible for new properties which make them exceptionally promising as versatile optical sources and detectors. However, the amount of light emission from nanotubes is much lower than initially expected and limits their use in optical devices. For single wall carbon nanotubes, every atom is situated on the surface, and the environment will therefore be of importance. The goal of this proposal is to understand which of the observed properties are intrinsic to the nanotubes and which ones depend on the environment. It is also of importance to measure and understand the role of the different nanotube species. Samples are prepared such that a single nanotube at a time will be studied, in order to avoid averaging. The project will train two graduate students and involve 4 undergraduate students yearly, who will participate both in direct hands-on nanotube fabrication and optical measurements, as well as in the development of web tools for calculating the types of lattice vibrations that can be detected optically.
The unusual electronic structure inherited from graphene, provides a multitude of electronic properties with both metallic nanotubes and semi-conducting nanotubes with varying band-gaps, promising as tunable optical sources and detectors. However, low quantum yield limits the current optical use of nanotubes. The goal of this proposal is to use optical methods such as Raman scattering, photoluminescence and photo-absorption to measure and understand the role of intrinsic nanotube properties and how they vary with chirality, and how those properties are affected by the environment. Samples are prepared such that a single nanotube at a time will be studied, in order to avoid averaging. The areas of interest are the environmental screening effects of excitions, the role of the dark excitons for the optical quantum yield and possibly its manipulation, and the different electronic dissipation pathways provided by phonon interactions. The project will train two graduate students and involve 4 undergraduate student yearly, who will participate both in direct hands-on nanotube fabrication and optical measurements, as well as in the development of web tools for calculating phonon dispersions, phonon density of states, and with help of group theory to identify which of the many of the tube's phonon modes that are Raman active.
