  We describe a pulsed measurement technique to suppress hysteresis for carbon
nanotube (CNT) device measurements in air, vacuum, and over a wide temperature
range (80-453 K). Varying the gate pulse width and duty cycle probes the
relaxation times associated with charge trapping near the CNT, found to be up
to the 0.1-10 s range. Longer off times between voltage pulses enable
consistent, hysteresis-free measurements of CNT mobility. A tunneling front
model for charge trapping and relaxation is also described, suggesting trap
depths up to 4-8 nm for CNTs on SiO2. Pulsed measurements will also be
applicable to other nanoscale devices such as graphene, nanowires, and
molecular electronics, and could enable probing trap relaxation times in a
variety of material system interfaces.
