Geometry Dependent Resistivity in Single-walled Carbon Nanotube Films Patterned Down to Submicron Dimensions

ABSTRACTWe demonstrate patterning of SWNT films down to 200 nm lateral dimensions using e-beam lithography and reactive ion etching with good selectivity and directionality and then we fabricate standard four-point-probe structures to characterize the resistivity of these films as a function of device geometry. The resistivity is found to be independent of device length for a given width and thickness, while increasing over three orders of magnitude compared to bulk films, as the width and the thickness of the films shrink. In particular, the resistivity of SWNT films starts to increase with decreasing device width below 20 μm, exhibiting an inverse power law dependence on device width at sub-micron dimensions. We explain this behavior by a purely geometrical argument. Although the “top-down” patterning of nanotube films allows for their use in sub-micron device structures and perhaps their integration into standard silicon fabrication technology, the resistivity scaling is an important effect that needs to be taken into account when fabricating small devices in which nanotube film transport characteristics play a vital role.