Doctoral Dissertations

Date of Award

5-2005

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Materials Science and Engineering

Major Professor

Michael L. Simpson

Committee Members

D. H. Lowndes, Philip Rack, Ward Plummer, Gregory Peterson

Abstract

Vertically aligned carbon nanofibers (VACNFs) have shown promise for use as field emission electron sources. Dual-gate field emission structures (triodes) have been fabricated and characterized. The electron beams can be successfully focused in these triodes. These studies show VACNF based field emission devices are promising for electron beam lithography applications. In this thesis, work is continued on triode device investigation. Methods to improve the device fabrication, to understand/optimize the device performance, and to repair defective triodes are presented.

Numerical simulation of the triode performance is included. Depth of field (DOF) of these triode structures is calculated by simulation and is determined to be ~5μm for the current triode structures. The DOF can be improved by employing thicker electrodes. The optimum beam radius is also reduced for thick electrodes. 3D modeling of the structure misalignment shows that a very small and well-converged beam is observed for the maximum shifts studied: 100nm focus electrode shift or 50nm VACNF shift, although astigmatism and coma-type aberrations will increase somewhat from these misalignments. The simulation results are promising and warrant further research on these devices.

Single-gate individual cathode-addressable devices are successfully fabricated. VACNFs are successfully grown on an insulating substrate instead of a conductive silicon substrate for this purpose. Electron field emission is demonstrated to be successful from these devices.

Several possible fabrication schemes to achieve fully self-aligning aperture formation in triode fabrication are designed and discussed. The best way to achieve self-alignment is to employ a process based on both chemical mechanical polishing (CMP) and reactive ion etching (RIE) selectively. Fully self-aligned devices are successfully fabricated in this manner. Repair on a missing/defective VACNF in triodes is shown to be promising using an electron beam-induced deposition (EBID) technique; both single and dual-gate devices with an EBID deposited nanoemitter are produced and function very well.

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