Unraveling packing-dependent surface potential contrast in a single-walled carbon nanotube bundle network

The surface potential of single-walled carbon nanotube (SWCNT) bundles is influenced by various factors, notably their arrangement during packing. Understanding this packing-dependent surface potential entails examining the interactions between individual nanotubes within a bundle and their collective effect on electrostatic properties. Our study delves into investigating the work function of SWCNT bundles, which can be modulated by factors such as the quantity and orientation of attached SWCNTs. Utilizing Kelvin probe force microscopy (KPFM) for characterization, we observed that the surface potential-and consequently, the work function-of SWCNT bundles varies with height and orientation. Our findings reveal that the surface potential undergoes changes based on the number of SWCNTs within a bundle. Moreover, the combination of parallel and crossed SWCNT bundles leads to distinct alterations in surface potential-an interesting experimental observation. Moreover, our demonstration reveals that applying an external bias to the SWCNT network splits ambient moisture into ions and protons, trapped within potential wells formed by the network of SWCNTs bound via van der Waals interaction. This mechanism leads to observing a persistent reverse current even after removing the external bias.