Photoconductivity of Single-Walled Nanotubes on Quartz Substrates

Photoconductivity measurements are used to study the electrical properties of carbon nanotubes on quartz substrates. Fabricating nanotube devices on quartz allows a measurement of the intrinsic photocurrent without any contribution from the substrate. We measure photocurrents of order nanoamps and a lower limit for the rise time of a SWNT diode device. Various measured rise times range from fast ($<$ 5 $\mu $s) to slow (800 $\mu $s), indicating that nanotube devices may be useful for high speed applications, but that the device configuration may play a critical role in the minimum achievable rise time. The special considerations for fabricating single nantoube devices on quartz will also be discussed.