Joseph A. Driscoll

First-principles study of field emission from carbon nanotubes and graphene nanoribbons

A real-space, real-time implementation of time-dependent density functional theory is used to study electron field emission from nanostructures. Carbon nanotubes and graphene nanoribbons are used as model systems. The calculations show that carbon nanotubes with iron adsorbates have spin-polarized emission currents. Graphene nanoribbons are shown to be good field emitters with spatial variation of the emission current influenced by the presence of passivating hydrogen.

A development environment for evolutionary robotics

Evolutionary robotics is an exciting new area of research with the potential to provide ways to build robots that are beyond our current design abilities. Instead of building robots from the ground up, as with other approaches, robot controllers are evolved using algorithms inspired by biological evolution. The purpose of this work is to develop a tool for the evolution of mobile robot controllers. The controllers are evolved in a realistic simulation. The evolutionary algorithms are provided by the GALib library. Testing demonstrates that the system is capable of producing useful robot controllers. Users can configure the system so that a variety of controller types can be evolved. With a system such as this, users can conduct a range of experiments without having to create custom software.

Time-dependent density functional study of field emission from nanotubes composed of C, BN, SiC, Si, and GaN.

Field emission from various types of nanotubes is studied by propagating the electronic density in real space and time using time-dependent density functional theory. Capped (5, 5) C, BN, SiC, Si, and GaN nanotubes are considered. The GaN, SiC, and Si nanotubes were found to be significantly better field emitters than C and BN nanotubes, both in terms of current magnitude and sharpness of peaks in the energy spectra. By analyzing the electronic structure of the various systems it is seen that the nanotubes with the highest currents have electron densities that extend significantly from the nanotube in the emission direction.