Electrodes for carbon nanotube devices by focused electron beam induced deposition of gold

Abstract

Individual carbon nanotubes (CNTs) often occur in randomly dispersed two-dimensional as well as three-dimensional configurations that make device fabrication difficult. Making electrical contact to such CNTs is of practical interest. To this end, we make contact to individual metallic single-walled carbon nanotubes (SWNTs) using the focused electron-beam-induced deposition (FEBID) of pure gold. The SWNTs are grown by chemical vapor deposition on a flat substrate, and the gold leads are made through FEBID using inorganic metallic precursor gas, chloro(trifluorophosphine)gold(I), or AuClPF3, in a high vacuum scanning electron microscope. The same scanning electron microscope is also used to image carbon nanotubes, allowing for simultaneous alignment. We find equivalent one-dimensional resistivities for the SWNTs of 10–15kΩ∕μm for both FEBID gold leads and leads deposited using conventional electron-beam lithography (EBL) and thermal evaporation of gold, suggesting similarly low contact resistances. We use electrostatic force microscopy to verify quantitatively similar contact resistances for one nanotube sample, 10(±6) and 54(±6)kΩ, for FEBID and EBL leads, respectively, with most voltage dropping across the long metallic SWNT.