Using pulsed and modulated photothermal radiometry to measure the thermal conductivity of thin films

Two techniques of photothermal radiometry (PTR) in front face configuration were used to determine the thermal conductivity of thin nanocrystalline films. The first technique relies on using modulated laser beam as a heating source. The second is based on pulsed laser heating where the pulse can be assimilated to a Dirac function. In the two measurement setups, the infrared radiation emitted from the heated surface of the sample is measured by an infrared detector. The thermal conductivity of CrN thin films prepared with various thicknesses by magnetron sputtering on silicon substrates was investigated by both techniques showing a dependence on the film microstructure. The thermal resistance at the film-substrate interface and intrinsic thermal conductivity of the films were identified by the two techniques and are in a very good agreement. In addition to the interface thermal resistance, the measurements revealed lower thermal conductivity of very thin films that can be attributed to presence of high amount of grain boundaries and other structural defects.