Recent studies in nanopiezotronics have indicated that strained graphene may exhibit abnormal flexoelectric and piezoelectric properties. Similar assumptions have been made with regard to the properties of carbon nanotubes (CNTs), however, this has not so far been confirmed. This paper presents the results of our experimental studies confirming the occurrence of a surface piezoelectric effect in multi-walled CNTs under a non-uniform strain. Using atomic force microscopy, we demonstrated the piezoelectric response of multi-walled CNTs under compression and bending. The current generated by deforming an individual CNT was shown to be −24 nA. The value of the surface potential at the top of the bundle of strained CNTs varied from 268 mV to −110 mV, depending on strain type and magnitude. We showed that the maximum values of the current and the surface potential can be achieved when longitudinal strain predominates in a CNT. However, increasing the bending strain of CNTs does not lead to a significant increase in current and surface potential, due to the mutual compensation of piezoelectric charges concentrated on the CNT side walls. The results of the study offer a number of opportunities and challenges for further fundamental research on the piezoelectric properties of carbon nanotubes as well as for the development of advanced CNT-based nanopiezotronic devices.
Aligned carbon nanotubes (CNTs) are among the most promising nanostructures in nanoelectronics. However, at the moment, CNTs have not received wide practical application for producing electronic devices, owing to the...
This chapter presents the results of experimental studies of the electrical, mechanical and geometric parameters of vertically aligned carbon nanotubes (VA CNTs) using scanning probe microscopy (SPM). This chapter also presents the features and difficulties of characterization of VA CNTs in different scanning modes of the SPM. Advanced techniques for VA CNT characterization (the height, Young's modulus, resistivity, adhesion and piezoelectric response) taking into account the features of the SPM modes are described. The proposed techniques allow to overcome the difficulties associated with the vertical orientation and high aspect ratio of nanotubes in determining the electrical and mechanical parameters of the VA CNTs by standard methods. The results can be used in the development of diagnostic methods as well as in nanoelectronics and nanosystem devices based on vertically aligned carbon nanotubes (memory elements, adhesive structures, nanoelectromechanical switches, emission structures, etc.).
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