Fabrication and Characterization of Carbon Nanotubes on Ceramic and Silicon Substrates for High Temperature Electronic Device Applications
Type of DegreePhD Dissertation
DepartmentElectrical and Computer Engineering
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This dissertation focuses on characterization and fabrication of multi-wall carbon nanotubes (CNTs) by DC plasma sputtering and thermal chemical vapor deposition techniques (CVD) on silicon (Si) and ceramic (Al2O3) substrates. CNTs have been attracting interest in research due to their electrical, chemical, and mechanical properties. They are considered as ideal field emission materials due to their high aspect ratio of diameter to length. They also possess excellent thermal conductivity and significantly high field emission stability. In this research we investigated their field emission characteristics by measuring current density vs field strength. We also studied their field emission properties when they are deposited on different substrates. The measurements were taken from room temperatures to 300oC. Furthermore, Fowler-Nordheim plots which are commonly used to describe the quantum mechanical tunneling process, of the fabricated CNTs are investigated in this study. In this work we have grown selective and non-selective CNTs by using traditional microfabrication technology on silicon and ceramic substrates. Catalyst layers of iron (Fe), tungsten (W), and graphite are deposited onto the substrates using a DC plasma sputtering system. In some cases W is used as the electrical contact of the sample on ceramic. After the metal film deposition, the substrate with the catalyst layers is transferred to the thermal CVD chamber for CNT growth. One of the driving forces behind using ceramic substrates to synthesize CNTs is to use CNTs in high temperature applications and extreme conditions. Due to the thermal properties of both CNTs and ceramic, this implementation is very promising for high temperature electronics applications. In the last chapter of the dissertation, possible CNT applications are discussed. We also included our experimental results of a CNT-based diode, where CNTs act as electron emitters supplying the seed electrons to turn it on and the preliminary results of the diode acting as an RFID tag, to this chapter.