M.S. (Master of Science)
Department of Electrical Engineering
This thesis discusses the different fabrication steps involved in producing ultra-fine cathodes that are suitable for cold field emission. A four-step nanofabrication process has been developed to obtain the cathodes with tip diameters ranging from 10nm to 20 nm. First, a mask is patterned on a 2-inch silicon wafer using monodisperse 1.18µm silica spheres. These particles are self-assembled using vortex-flow enabled assembly technique to form close-packed monolayers. Then the silicon is etched using a reactive ion etching technique. An inductively coupled plasma etcher is used to perform anisotropic and isotropic etching. The etching recipes used are chosen such that they are more selective to silicon compared to silica to form smooth hour-glass shaped pillars. These pillars are further sharpened by eliminating the silica mask using a buffer oxide etch solution and then sharpening the necks of the pillars through multiple oxidation steps. Various oxidation times are experimented to achieve fine aspect-ratio cathodes. To improve the field enhancement factor and to increase the wear-resistance of the silicon cathodes, a 25nm tungsten film is deposited on which a diamond film is deposited through Chemical Vapor Deposition. The fabricated cathodes are tested under ultra-high vacuum conditions for field emission under an applied electric field of 3KV-6KV. Thereby, the field enhancement factor for these cathodes is calculated using Fowler-Nordheim equations.
Valluri, Srujana, "Fabrication of Ultra-Fine Cathodes For Cold-Field Emission" (2019). Graduate Research Theses & Dissertations. 7749.
Northern Illinois University
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