Sublayer material as a critical factor of piezoelectric response in nitrogen-doped carbon nanotubes

Abstract

Recent studies have shown that nitrogen-doped carbon nanotubes (N-CNTs) exhibit anomalous piezoelectric properties, which opens broad prospects for their use in the field of nanopiezotronics. In this work, we have demonstrated the effect of the material of the conducting sublayer (titanium, titanium nitride, molybdenum, and chromium) on the structural and piezoelectric properties of N-CNTs. It was found that the sublayer material significantly affects the nitrogen concentration and the type of defects formed in N-CNTs, which in turn has a decisive effect on the magnitude of the piezoelectric strain coefficient of N-CNTs. It is shown that the maximum piezoelectric strain coefficient is observed for CNTs grown on a molybdenum sublayer, which is associated with the active formation of pyrrolic nitrogen in the nanotube structure in the process of growth. The magnitude of the piezoelectric strain coefficient N-CNTs increases from 5.6 to 21.5 pm/V with an increase in the concentration of pyrrolic nitrogen from 10 to 39%. An increase in the piezoelectric strain coefficient of N-CNTs, in turn, leads to an increase in the generated current from 12 to 138 nA. The results obtained can serve as a basis for the development of energy-efficient nanogenerators based on nitrogen-doped CNTs.