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 mu S mu m(-1)) and decent on current per nanotube (similar to 1 mu A per tube) together with high on/off ratios at a drain bias of -1V.