Semiconducting enriched carbon nanotube align arrays of tunable density and their electrical transport properties

We demonstrate assembly of solution processed semiconducting enriched (99%) single walled carbon nanotubes (s-SWNT) in an array with varying linear density via ac-dielectrophoresis and investigate detailed electronic transport properties of the fabricated devices. We show that (i) the quality of the alignment varies with frequency of the applied voltage and that (ii) by varying the frequency and concentration of the solution, we can control the linear density of the s-SWNTs in the array from 1/{\mu}m to 25 /{\mu}m. The maximum linear density of 25 s-SWNT /\mum reported here is the highest for any aligned semiconducting array. The DEP assembled s-SWNT devices provide opportunity to investigate transport property of the arrays in the direct transport regime. Room temperature electron transport measurements of the fabricated devices show that with increasing nanotube density the device mobility increases while the current on-off ratio decreases dramatically. For the dense array, the device current density was 16 {\mu}A/{\mu}m, on-conductance was 390 {\mu}S, and sheet resistance was 30 k{\Omega}/\square. These values are the best reported so far for any semiconducting nanotube array.