The detection of single ions has, for many years, been the domain of large devices such as the Geiger counter, and to date, there have been no studies investigating the effects of ions on materials and devices at the single-ion level, despite the widespread use of gaseous ions to modify material surface properties, for instance by corona discharge. Here, we report on single gaseous ion adsorption onto individual carbon nanotube field effect transistors, which, due to the severely restricted one-dimensional current path, experience discrete, quantized resistance increases of over two orders of magnitude [1]. Switching events were observed during exposure to lightly ionized nitrogen, helium, oxygen, argon and air. This is in contrast to single neutral atom adsorption detection techniques, which have shown only small, barely detectable responses. Only positive ions cause changes, by the mechanism of ion potential induced carrier depletion, which is supported by density functional and Landauer transport theory. Our observations reveal a new single-ion/CNT heterostructure with novel electronic properties, and demonstrate a powerful new system for studying ion adsorption dynamics at the single-ion level.

[1] Bushmaker, A. W. et al. Single-ion adsorption and switching in carbon nanotubes. Nature Communications, 7, 10475, DOI: 10.1038/ncomms10475 (2016).