Electrical Measurement of Water Assisted Ion Desorption and Solvation on Isolated Carbon Nanotubes

With continued reduction in the feature size of device structures we are quickly approaching the one-dimensional limit of electrical conduction. In this regime it becomes increasingly important to study the effects of individual dopants and defects on device performance. Recent studies on the electrical properties of suspended carbon nanotube field-effect transistors (CNT-FETs) have revealed extreme sensitivity in device conductivity in the presence of individual gaseous ions adsorbed at the nanotube surface. We will present an investigation on the mean residence time of gaseous ions adsorbed on the surface CNT-FETs with and without native surface water layers that exist in atmospheric conditions. Devices dehydrated by various methods were all found to have substantially higher mean ion residence times. We propose that native water molecules in ambient conditions provide a reduction pathway for incoming gaseous ions, yielding Hydronium ions (H₃O⁺). We characterize the interaction between these ions with the CNT-FET surface via large switching events in device conduction and compare to measurements taken on desiccated devices.