Electron field emission properties from nanoengineered structures.

This work is mainly divided into three parts. Firstly, with the aim of integrating electron field emitter with other circuit elements on a single chip, silver-silicon dioxide (Ag-SiO2) nanocomposites are fabricated and studied. The Ag-SiO2 nanocomposites are synthesised by Ag implantation into thermally oxidised SiO2 layers on Si substrates and their fabrication processes are fully compatible with existing integrated circuit technology and their threshold fields are less than 20 V/mum. The local field enhancement mechanisms were studied and the fabrication processes of these layers optimised. Secondly, the electron field emission (FE) properties of two-dimensional quantum confinement structure were studied. Band gap modulated amorphous carbon (alpha-C) nanolayers were synthesised by pulsed laser deposition. In these structures, electrons are confined in a few nm thick low band gap sp2 rich alpha-C layer, which is bound by the vacuum barrier and a 3 nm thick high band gap sp3 rich alpha-C base layer. Anomalous FE properties, including negative differential conductance and repeatable switching effects, are observed when compared to control samples. These properties will be discussed in terms of resonant tunnelling and are of great interest in the high-speed vacuum microelectronic devices. Finally, due to the interesting electrical transport properties and rare FE characteristics of metal quantum dots (QDs), cobalt QDs were synthesized in a SiO2 matrix by ion implantation. Staircase-like current-field characteristics were observed for the first time from these samples and give an experimental insight into existing Coulomb Blockade effects in the metal QDs during the FE process. Moreover, these samples also achieve excellent FE properties with threshold fields less than 5 V/mum and are comparable with other popular FE materials.