Carbon nanotubes, hollow cylindrical structures made of carbon atoms with diameters in the order of a few nanometres, are attractive candidates for electron emission applications. A detailed characterization of the phenomenon so-called electron-stimulated field-emission from carbon nanotubes is presented in this thesis. An electron beam hitting the tip of a nanotube biased near the threshold of field-emission can stimulate the emission of a large number of electrons from the nanotube tip. The result of this interaction is that high electron gains can be obtained with very small stimulating electron beam currents. Electron gains of up to 2300 were recorded. This is important as this effect could form the basis of several vacuum nanoelectronic devices. Possible direct and indirect electron-nanotube interaction mechanisms responsible for this high gain are discussed and substantiated through simulations. The design and assembly of an ultra high vacuum apparatus for more controlled future experiments is also presented. Finally, I wish to express my love and gratitude to my beloved wife; for her understanding and endless love, throughout the duration of my studies. xi Dedication To my wife Alison xii Statement of Co-Authorship Chapters 1, 3 and the Appendix A were written by the author. Chapter 2 is a paper submitted for publication, which is co-authored by myself, Parham Yaghoobi, Bertin Wong and Dr. Alireza Nojeh. Parham Yaghoobi and Berting Wong put together most of the experimental apparatus. Particularly, they assembled the scanning electron microscope where all the experiments for this paper were performed. Bertin Wong also performed some of the initial experiments in collaboration with me. I helped setting up the data collection system and performed all the experiments, derivations, simulations and analysis under the guidance of Dr.

Single crystalline GaN nanowires were synthesized using chemical vapor deposition. Devices containing individual GaN nanowires were fabricated using contact printing. The local turn-on electric field at the tip of the GaN nanowires was compared to that of other nanomaterials. The quality of contact between GaN nanowires and metal electrodes was found to affect the field-emission behavior significantly. It was also observed that the field-emission behavior of individual GaN nanowires follows the conventional Fowler-Nordheim model in the range of applied electric fields. V

The authors report electron emission from forests of vertically aligned multiwalled carbon nanotubes under irradiation by continuous wave green and blue lasers with relatively low power and intensity (maximum intensity of ∼320 W cm−2). The electron emission shows nonlinear increase with laser power for both laser wavelengths of 488 and 532 nm. Thermionic emission and photofield-emission appear to play a role in different sections of the current-voltage characteristics.

We demonstrate photoelectron emission from millimeter-long forests of vertically aligned multiwalled carbon nanotubes using 266 nm light, which illuminates the forests from the side. We have measured quantum efficiencies in the order of ∼10−5 at low fields (pure photoemission) and ∼10−3 at an applied field of 0.3 V μm−1, which are 2–4 orders of magnitude higher than those obtained from films of randomly oriented nanotubes, and approach the quantum efficiency of semimetal photocathodes. Through optical simulations we show that 266 nm light is absorbed within the first few layers of the nanotube forest.

Carbon nanotubes are attractive candidates for electron field-emitters due to their high aspect ratio, mechanical stability, and electrical conductivity. It has previously been shown that an electron beam hitting the tip of a carbon nanotube biased near the threshold of field-emission can stimulate the emission of a large number of electrons from the nanotube tip. Here we report on similar experiments on arrays of free-standing multi-walled carbon nanotubes (nanotube forests) interacting with a scanning electron microscope's primary beam. Electron gains of up to 19,000 were obtained. This can enable applications such as electron detection and multiplication, and vacuum transistors.