Modulated IR Radiometry Applied to Study \text{ TiO}_{2} Coatings with Gold Nanocluster Inclusions

In this work Au:\(\text{ TiO}_{2}\) thin films prepared by dc reactive magnetron sputtering were studied. The thin films, with an amount of gold of about 15 at %, were subsequently annealed at constant temperatures between \(200\,^{\circ }\text{ C}\) and \(800\,^{\circ }\text{ C}\), are here analyzed with respect to their thermal behavior. The changes of the material properties with increasing annealing temperature from initially amorphous to a gradually increasing crystalline structure and the formation of nanoclusters and gold nanoparticles of increasing size, from 5 nm to 17 nm, are analyzed with the help of the phase lag signals measured by modulated IR radiometry. The obtained results seem to indicate the formation of strong subsurface heat sources, which can be explained with the help of the surface plasmon resonance effect and which can be described by the theory of semitransparent coatings, with effects of semi-transparency both in the visible and the infrared spectrum.