Influence of thermal stresses on electron transport in carbon–polymer nanocomposite films

The influence of two types of thermal stress in carbon–polyimide nanocomposite films (C–PI), where one is due to internal residual stresses on freestanding films arising from the fabrication process and the other due to adhesion of these films, on different substrate materials has been presented. Freestanding C–PI films as well as those supported on rigid and flexible substrates have been prepared and found to have temperature dependant electrical behaviours depending on the physical properties of the substrate such as coefficient of thermal expansion. Modelling of the C–PI nanocomposite film prepared on silicon using finite element analysis (FEA) revealed the presence of residual stresses within the composite film arising from the differences in the thermomechanical properties of the composite film and the substrate. Here, it is proposed that residual stresses affect the electronic band structure of the nanocomposites thereby influencing charge transfer between the conducting particles leading to observed changes in the hopping energies for these nanocomposite films on the different substrates.