Vibrational and Electronic Aspects of Carbon Nanotubes and their Interactions

碳纳米管有几个极端的特性，从机械强度、热传导和电子传导，到非常不寻常的电子结构。它们不同寻常的电子结构继承自石墨烯，为不同的纳米管物种提供了大量的电子特性。纳米尺寸的电子管具有新的特性，使其成为非常有前途的多功能光源和探测器。然而，纳米管的光发射量远低于最初的预期，限制了它们在光学器件中的应用。对于单壁碳纳米管，每个原子都位于表面，因此环境将是重要的。本提案的目标是了解观察到的特性中哪些是纳米管固有的，哪些取决于环境。测量和了解不同种类的纳米管的作用也很重要。样品的制备使得每次只研究一个纳米管，以避免平均。该项目每年将培训两名研究生和四名本科生，他们将直接参与纳米管制造和光学测量，以及用于计算光学检测到的晶格振动类型的网络工具的开发。从石墨烯继承的不寻常的电子结构，提供了金属纳米管和半导体纳米管的多种电子特性，具有不同的带隙，有望作为可调谐的光源和探测器。然而，低量子产率限制了纳米管目前在光学上的应用。本课题的目标是利用拉曼散射、光致发光和光吸收等光学方法来测量和理解纳米管固有性质的作用，以及它们如何随手性变化，以及这些性质如何受到环境的影响。样品的制备使得每次只研究一个纳米管，以避免平均。感兴趣的领域是激发的环境筛选效应，暗激子对光量子产率的作用及其可能的操纵，以及声子相互作用提供的不同电子耗散途径。该项目每年将培训两名研究生和四名本科生，他们将直接参与纳米管的制造和光学测量，以及用于计算声子色散、声子态密度的网络工具的开发，并在群论的帮助下确定许多管的声子模式中哪些是拉曼活跃的。

Non-technical summaryCarbon 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. Technical summaryThe 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.