Nonlinear Field Enhancement factor of Carbon Nanotubes (CNTs) in Vacuum and Partial Pressure
Type of Degreethesis
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Carbon nanotubes (CNTs) have attracted much attention because of their unique electrical properties and their potential applications. Large aspect ratios of CNTs together with thermal conductivity high mechanical strength and chemical inert are advantageous for applications to the field emitter. In this work carbon nanotubes are studied in order to develop cold cathode materials with efficient field emission characteristics. Randomly aligned Multi-Walled carbon nanotubes (MWCNTs) are fabricated using chemical vapor deposition (CVD) under different growth conditions. These nanotubes are then tested for their field emission characteristics at different pressures ranging from 2x10-7 Torr to 20x10-3 Torr in Helium gas. Effects of different gases at different pressure and the catalyst thickness on the field emission properties of carbon nanotubes are studied and results are presented. Fowler-Norheim (FN) plots revealed nonlinear slopes for all the samples tested in different background pressures. It is known that the slope of the FN plots gives information about the field enhancement factor of the surface. Therefore, the nonlinearity is attributed to a nonlinear field enhancement factor. This data is used in determining a proper cold cathode material to be used as a trigger electrode for pseudospark switches.