Fabrication and Characterization of Novel Nanoscale Field Emission Arrays
In this thesis we have demonstrated novel nanoscale cold cathode devices based on rare-earth monosulfides, gold nano pinetree like and carbon nano pearl arrays. We first developed a MEMS based cold cathode device based on pulsed laser deposition (PLD) of lanthanum monosulfide (LaS). The device exhibited a largest field emission (FE) current of 5x10-7A which is suitable for flat panel displays. It can also be used to develop a three terminal device providing gate control of the field emission current. Then, in an effort to fabricate nanowire arrays of LaS for efficient field emission, we discovered the formation of the trimodal arrays where three different nanoscale arrays of LaS- nanodots, nanodomes and nanowires have been simultaneously fabricated by PLD of LaS on flexible self-assembled nanoporous alumina templates. The nanodots with a density of 10^10/cm^2 and the nanodomes with a density of 10^9/cm^2 are formed on the surface of the template while the nanowires are formed inside the pores with a density of 10^10/cm^2. The LaS nanodots and the nanodomes formed on the surface acted as efficient field emitters by reducing the threshold voltage by ~3.5 times for the same amount of field emitted current compared to the LaS thin films deposited on silicon substrates.
During the process of investigating the formation of trimodal arrays of LaS, we have observed multi level and multi modal self assembly on surface of the nanoporous alumina. Specifically three distinct unique nanoscale features have been observed. The first feature is the self assembly of carbon nanopearls in the form of nanotentacles and nanonecklaces on an array of nickel nanodots and nanodomes. The second feature is the nanopine tree like structures formed by e-beam evaporation of gold onto the alumina template. Both these features have emitted stable field emission current. The third features is the nanoblade like structures formed by e-beam evaporation of nickel on the alumina template. A stable field emission current could not be obtained which can be explained by the reactivity of nickel to the adsorbed species. While the CNP nanotentacle and Au nanopinetrees can be used to form novel inexpensive arrays of high density cold cathodes, the nickel nanoblade like features cannot be used as planar cathodes.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:trimodal field emission emitters self assembly oleds
Date of Publication:01/01/2008