Photoconductivity studies of carbon nanotubes on quartz substrates

This thesis presents photoconductivity measurements used to study the properties of carbon nanotubes on quartz substrates. Two types of devices are used. The first class consists of an individual bundle of carbon nanotubes aligned from suspension between electrodes. The second consists of a single-walled nanotube (SWNT) grown via chemical vapor deposition and electrically contacted using novel lithographic techniques. Fabricating nanotube devices on quartz allows optical measurements of the nanotube without any contribution from the substrate. The special considerations for fabrication on quartz substrates are discussed.;The photoresponse of bundles is a useful measure of the coupling between individual SWNT in the bundle. Measured photocurrents are of order picoamps and rise times are as long as 10 ms. We propose that the longer-than-expected rise times are due to intertube coupling.;Individual SWNT are expected to have very high drift velocities, making SWNT an attractive material for fast-switching device applications. We measure photocurrents of order nanoamps and an upper limit for the rise time of a SWNT diode device. The measured rise times are both fast (<5 μs) and slow (800 μs) indicating that nanotube devices can be used for high speed applications, but that the device configuration may play a critical role in the minimum achievable rise time.