Study of adhesion of vertically aligned carbon nanotubes to a substrate by atomic-force microscopy

The adhesion to a substrate of vertically aligned carbon nanotubes (VA CNT) produced by plasmaenhanced chemical vapor deposition has been experimentally studied by atomic-force microscopy in the current spectroscopy mode. The longitudinal deformation of VA CNT by applying an external electric field has been simulated. Based on the results, a technique of determining VA CNT adhesion to a substrate has been developed that is used to measure the adhesion strength of connecting VA CNT to a substrate. The adhesion to a substrate of VA CNT 70–120 nm in diameter varies from 0.55 to 1.19 mJ/m$^2$, and the adhesion force from 92.5 to 226.1 nN. When applying a mechanical load, the adhesion strength of the connecting VA CNT to a substrate is 714.1 $\pm$ 138.4 MPa, and the corresponding detachment force increases from 1.93 to 10.33 $\mu$N with an increase in the VA CNT diameter. As an external electric field is applied, the adhesion strength is almost doubled and is 1.43 $\pm$ 0.29 GPa, and the corresponding detachment force is changed from 3.83 to 20.02 $\mu$N. The results can be used in the design of technological processes of formation of emission structures, VA CNT-based elements for vacuum microelectronics and micro- and nanosystem engineering, and also the methods of probe nanodiagnostics of VA CNT.