Fringing-field dielectrophoretic assembly of ultrahigh-density semiconducting nanotube arrays with a self-limited pitch

One key challenge of realizing practical high-performance electronic devices based on single-walled carbon nanotubes is to produce electronically pure nanotube arrays with both a minuscule and uniform inter-tube pitch for sufficient device-packing density and homogeneity. Here we develop a method in which the alternating voltage-fringing electric field formed between surface microelectrodes and the substrate is utilized to assemble semiconducting nanotubes into well-aligned, ultrahigh-density and submonolayered arrays, with a consistent pitch as small as 21±6 nm determined by a self-limiting mechanism, based on the unique field focusing and screening effects of the fringing field. Field-effect transistors based on such nanotube arrays exhibit record high device transconductance (>50 μS μm −1 ) and decent on current per nanotube (~1 μA per tube) together with high on/off ratios at a drain bias of −1 V. Carbon nanotubes offer a route to further reducing the size of electronic components. Here, the authors demonstrate a method to assemble semiconducting nanotubes into well-aligned, ultrahigh-density and uniform arrays using an alternating electric field between surface microelectrodes and the substrate.