Thermal diffusivity characterization of semiconductive 1D micro/nanoscale structures

•TET model for nonlinear ρe∼T relation of semiconductive micro/nanoscale materials.•Robust thermal diffusivity (α) measurement by TET using the nonlinear ρe∼T model.•First time thermal diffusivity determination at the zero temperature rise limit.•α∼T trend for graphene film is well interpreted by the thermal reffusivity theory.•α∼T trend for SWCNT mat reveals strong structure deterioration with T decreasing. The transient electrothermal (TET) technique was developed and has been widely used for measuring the thermal diffusivity of fiber- and film-like materials at the micro/nanoscale. Upon step-current heating, the measured voltage-time (V-t) of the sample usually follows a sole increasing or decreasing trend, depending on the temperature coefficient of its electrical resistivity (θT = dρe/dT, ρe: electrical resistivity, T: temperature). Past physical mode for the V-t profile is based on an assumption that θT is constant during TET measurement, which applies to a large variety of materials. However, for semiconductive materials, θT depends on the charge carrier density and scattering time, and both vary with temperature. Therefore, θT has very strong nonlinear change with temperature, sometimes changes sign during TET measurement. This leads to abnormal V-t profiles that have never been addressed well, thereby making TET measurement not applicable for such scenarios. In this work, a new physical model is developed to consider the strong nonlinear relation between ρe and T to the third order. Our numerical modeling firmly proves the validity of this new model. Thin films of graphene (GreF) and single-walled carbon nanotube (SWCNTs) mat are measured using the TET technique over a wide temperature range: 84.5–690.9 K for the GreF, and 12–290 K for the SWCNT film. At a specific temperature for each sample, a semiconductive-to-metallic transition comes about and manifests in the resistance-temperature response, hence leading to abnormal TET signals. These TET signals are perfectly fitted using our nonlinear θT ∼ T model to determine α. Intriguingly, the determined α of the GreF for the transition phase follows the overall α∼T trend, confirming the robustness of the model. The obtained α∼T trend is interpreted well using the thermal reffusivity theory and structure deterioration under temperature change. This work significantly extends the capability of TET to semiconductors for α measurement. Also, the new methodology developed for obtaining α at zero temperatu