Patterning and Characterization of Carbon Nanotubes Grown in a Microwave Plasma Enhanced Chemical Vapor Deposition Chamber

This research studies the growth of carbon nanotubes (CNT) from a nickel catalyst to be used on a field emission device. This thesis can be divided into three sections: the construction of a vacuum chamber for field emission testing, the design and fabrication of a triode structure to enable improved electron emission, and the pretreatment and growth of CNTs. To experimentally test the field emission of CNTs, a vacuum chamber must attain a vacuum of at least 10-5 torr. Our vacuum chamber designed and built achieved a maximum, final pressure of 10-8 torr. A triode structure was designed to pattern the CNTs to improve electron emission. A silicon wafer is used to fabricate the cathode and gate of the device while a quartz wafer is used as the anode. Through photolithography patterning of the gate, CNT growth occurs only in the defined locations. To better understand CNT growth, a study was performed using a hydrogen pretreatment on sputtered and electroplated nickel catalyst on silicon at various thickness in a microwave plasma enhanced chemical vapor deposition to determine the effects of this pretreatment. Nickel catalyst of 50, 100, and 200 ºA were treated with hydrogen and the formation of nano islands was achieved when using sputtered films. As the nickel catalyst thickness increases, the pretreatment time must also be increased to get favorable granule sizes and densities necessary for CNT growth. The 50 and 100 ºA nickel samples granulated to 25 and 58 nm showed high growth densities while the 200 ºA samples granulated to 180 nm showed marginal CNT growth. We also established the diameter of the multi walled CNTs grown correlated well to the size of the catalyst granules. The CNTs to be used in the triode design needed to be between 1.5 and 1.8 µm to avoid shorts between the gate and the CNTs. To achieve this, CNTs with a length of 1.5 µm were successfully grown by flowing methane for exactly two minutes