Nanostructure characterization by PA&PT

Heat transport at nanoscale is of importance for many nanotechnology applications [1]. There are typically two current problems related to this subject in nanophotonics: the first problem, of fundamental interest for semiconductor lasers [2], is the removal of the heat generated to maintain the functionality and reliability of these devices. The efficient evacuation of heat in the nanostructures is of crucial importance in order to avoid large thermal stresses devastating for the lifetime of the whole device. The second problem is to utilize nanostructures to manipulate the heat flow for thermoelectric energy conversion and thermophotovoltaic power generation. Here one has the inverse requirement, i.e. to limit thermal diffusion in order to guarantee a high energy conversion efficiency. Considerable efforts are nowadays to discover new geometries with a huge number of internal interfaces and thermal barriers in order to increase the thermal resistance. The study of the heat transport in such nanostructures is here performed by applying photothermal techniques. Photothermal radiometry is here applied to localize the internal heat sources where the light is absorbed and to measure the sample effective thermal diffusivity. In this work we discuss the results obtained on opals [3-5] and carbon nanotubes.