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Synthesis, Field Emission and Associated Degradation Mechanisms of Tapered ZnO Nanorods
Gregory Michael Wrobel, M.S.
University of Connecticut, 2011
Modern development of field emitter arrays (FEA) has been made possible, partly thanks to the synthesis and development of one-dimensional (1D) nanostructures. High aspect ratio 1D nanostructures effectively amplify the electric field at the emitter tips, allowing electrons to be extracted at relatively low electric field. An inexpensive and rationally-controlled method to synthesize FEAs may permit commercial development of the field emission display (FED) technology, which can potentially outperform modern liquid crystal display (LCD) technology.
In this thesis work, we have developed a low-cost approach to produce large-scale ZnO nanorod FEAs, and systematically studied correlated degradation mechanisms including, exposure to gas species at high-voltage, and high-current emission.
Nanorods of ZnO were grown directly from iron and copper substrates by solution processing, without surface pre-treatment such as seed or catalyst layer. Field emission measurements show high current density and low turn-on voltage. Annealing under vacuum effectively lowers turn-on voltage and enhances the maximum current density up to two orders of magnitude, as compared to initial field emission characteristics.
Two typical field emitter degradation mechanisms, including exposure to atmospheric gas species (O2, N2, and H2) during field emission and high current induced degradation of the emitter tips, have been studied experimentally and theoretically. Experimental results suggest the presence of each gas species suppress the field emission current, which is supported by density functional theory (DFT) calculations. A tip-degradation phenomenon of ZnO nanorod FEAs has been observed during high-current field emission, which is most likely induced by a resistive joule heating process, which could result in a steady state temperature at the nanorod tip above the melting point of ZnO as suggested by calculation.
This thesis work provides insight to better help understand how these tapered ZnO nanorods perform as field emitters and determine if they’re suitable for use as a commercial field emission source.
Wrobel, Gregory M. Mr., "Synthesis, Field Emission and Associated Degradation Mechanisms of Tapered ZnO Nanorods" (2011). Master's Theses. Paper 162.