Selective Deposition and Shear Assisted Alignment of Semiconducting Carbon Nanotubes Using Chemical and Topographical Features

Selective deposition of semiconducting carbon nanotubes (s-CNTs) into densely packed, aligned arrays of individualized s-CNTs is necessary to realize their potential in semiconductor electronics. We report the combination of chemical contrast patterns, topography, and pre-alignment of s-CNTs via shear to achieve selective-area deposition of aligned arrays of CNTs. Alternate stripes of surfaces favorable and unfavorable to s-CNT adsorption were patterned with widths varying from 2000 nm down to 100 nm. When the chemical and topographical contrast patterns are reduced to less than the width of individual nanotubes (≤ 500 nm), confinement effects become dominant enabling the selective-area deposition of much more tightly aligned CNTs (~7 degrees). At a trench width of 100 nm, we demonstrate the lowest standard deviation in alignment degree of 7.6 ± 0.3° at a deposition shear rate of 4,600 s-1, while maintaining an individualized s-CNT density > 30 CNTs µm-1. Chemical contrast alone enables selective area deposition but chemical contrast in addition to topography enables more effective selective area deposition and stronger confinement effects, with the advantage of removal of nanotubes deposited in spurious areas via selective lift-off of the topographic features. These findings provide a methodology that is inherently scalable, and a means to deposit spatially selective, aligned s-CNT arrays for next-generation semiconducting devices.