Tailoring the temperature coefficient of resistance of flame-formed carbon nanoparticle thin films by electric field-assisted deposition

The electric-field assisted deposition is successfully proposed as a method for the manufacturing of carbon nanostructured films with tunable properties, benefiting from the superimposition of electric fields on the thermophoretic deposition. Morphology, optical, and thermo-resistive properties of the carbon nanoparticle (CNP) films have been studied by UV–vis Absorption Spectroscopy, Scanning Electron Microscopy, Atomic Force Microscopy, and Current-Voltage analysis. In comparison to thermophoresis alone, the introduction of an electric field results in a six-fold increase in the deposition rate characterized by a non-linear film growth influenced by a three-fold augmentation in surface roughness and polarization effects. Notably, the surface morphology of the CNP films undergoes modification, exhibiting larger grains and a reduced optical band gap energy. Moreover, while maintaining a non-ohmic behaviour, the electric field plays a crucial role in increasing by about two orders of magnitude the electrical conductance of CNP films at ambient temperature. This effect is accompanied by a decrease in temperature sensitivity, attributed to the low and nearly temperature-independent activation energy for the tunneling of electrons in the percolative network. In summary, electric-field assisted deposition is a promising approach to tailor the thermal response of CNP films, which could be beneficial for the development of next-generation sensors.