The Research and Development of Sub-Micron Gap Nanodiamond Lateral Field Emission Diodes

Abstract

This dissertation focuses on the study of electron field emission from chemical vapor deposition (CVD) nanodiamond and the development of sub-micron gap lateral nanodiamond vacuum field emission diodes. A procedure was developed for optimizing nanodiamond film for fine lithography patterning and two procedures were developed for incorporating electron beam lithography (EBL) into the device design and fabrication. The successful fabrication of smooth nanodiamond films with grain sizes as small as ~10 nm and the achievement of sub-volt turn-on, sub-micron gap delineation for varied lateral diode cathode configurations are reported.

To identify the best nanodiamond film structure for use as an emitter material substrate, the underlying conduction mechanisms were discussed first. A collection of research on nitrogen-incorporated nanodiamond supports the existence of a hybrid nanostructure, reminiscent of our past reported MIM model, for low field emission. Practical CH4/H2-based chemical vapor deposition processing was applied to define various morphologies of diamond thin-film configurations followed by an analysis of the macroscopic field emission performance of each film as compared to the corresponding changes in binding energy and sp2/sp3 content. X-ray photoelectron Spectroscopy (XPS) and Raman spectroscopy were used for monitoring the deviations across the various diamond film configurations.

Sub-micron emission gap lateral field emission diodes derived from the optimized nanodiamond provide an alternative means of accomplishing electronics that operate at low voltages. In this work, electron beam lithography was introduced for structure definition on CVD-diamond. Processes were developed to fabricate laterally arranged nanodiamond field emission diodes using EBL patterning. The sub-micron gap delineation showed excellent uniformity for different cathode configurations. A ~0.6 V turn-on was observed as the anode-cathode inter-electrode distance was scaled from 1.5 µm down to 500 nm. The effect of changing the anode-cathode gap was observed in I-V characteristics, with a clear deviation from Fowler-Nordheim tunneling emission as the anode-cathode distance was reduced.

Reducing the inter-electrode spacing to the sub-micron range offers new and exciting opportunities for nanodiamond lateral device applications due to the high field strengths that can be achieved at low applied bias. The unique characteristics of the devices include interesting non-Fowler-Nordheim emission behavior that indicate a lowered potential barrier for field-enhanced thermionic emission and space charge limiting current at the diamond-vacuum interface.