Photoinduced heating of thin nitrogen-polymer films

In this work, the photo-induced heating of polymer films functionalized with azo-chromophore molecules has been studied for the first time. We have characterized the photoinduced heating of free-standing thin films with the use of scanning thermal microscopy with nanometer resolution. It has been shown that the film of 800 nm thickness being irradiated by resonant laser radiation (532 nm) and the power of 25 mW/cm$^2$ is heated by 1.7 K. Furthermore, a method has been introduced for determining the glass transition temperature of thin ($<100$ nm) polymer films based on thermo-induced atomic force microscopy (thermal-assisted AFM). In the proposed approach, the change of the phase of oscillating AFM cantilever has been used to determine the glass transition temperature. An anomalous decrease in the glass transition temperature has been shown for both free-standing and supported azobenzene-functionalized polymeric thin films.