Mobility enhancement in carbon nanotube transistors by screening charge impurity with silica nanoparticles

Ionic surfactants have been frequently used for nanotube device fabrication owing to their high efficiency in dispersing SWNTs. Surfactants are also widely adopted for state-of-the-art density gradient ultracentrifugation- and dielectrophoresis-based nanotube separation techniques. However, the residual surfactants on nanotubes have been speculated to degrade the electrical performance of SWNT devices. Conventional methods, such as extensive washing or thermal treatment, are not able to efficiently remove the residual surfactants. In this article, we reveal that a thin layer of polydimethylsiloxane (PDMS) containing silica and ionic liquid coated on SWNT network field-effect transistors (FETs) is able to largely enhance the device mobility (about 3-4 times) and suppress their hysteresis. The enhancement in electrical properties of SWNT FETs is due to the screening of residual charges by the silica/liquid ion mixture.