Carbon Nanotube Devices: Growth, Imaging, and Electronic Properties

Abstract

This dissertation focuses on growth, fabrication, and electronic characterization of carbon nanotube (CNT) devices. A technique for imaging CNTs on insulating substrates with the scanning electron microscope (SEM) will be described. This technique relies on differential charging of the CNT relative to the surrounding insulator. In addition, it is not only quicker than using scanning probe microscopy (SPM), but is also useful for identifying conducting pathways within an assortment of CNTs and metallic contacts. CNT field effect transitors (FETs) fabricated on strontium titanate gate dielectric show transconductances normalized by channel width of 8900 S/m, greatly exceeding that in Si FETs. Intriguingly, the transconductance cannot be explained within the conventional FET or Schottky-barrier models. To explain this, it is proposed that there is Schottky-barrier lowering due to high electric fields at the nanotube/contact interface. Exploring novel CNT-FET lithography, I demonstrate focused electron beam induced deposition (FEBID) of pure gold for CNT device electrodes. In examination of the CNT/electrode interface, equivalence between FEBID leads and leads deposited using conventional electron beam lithography is found with the majority device resistance in the CNT. Lastly, CNTs are suspended across wide trenches (>100 microns). These trenches are formed without lithography or etching and have metallic leads on either side of the trench for electrical transport measurements. Using a mechanical probe as a mobile gate, electrical transport can be performed on these suspended CNT devices, which show minimal hysteresis consistent with the absence of charge trapping.