Sintering of thin titanium dioxide nanoparticle films via photothermal processing with ultraviolet continuous-wave lasers

Photothermal laser processing of thin films of anatase titania nanoparticles (TiO2 NPs, diameter: 8–10 nm) with a thickness of about 500 nm is addressed. Laser processing in ambient air is carried out using a microfocused continuous-wave laser setup operating at a wavelength of 355 nm and a 1/e laser spot size of 1.6 μm. In conjunction with scanning electron microscopy, this approach provides a highly reproducible and convenient means in order to modify the local film structure and study the dependence of the resulting film morphology on the laser parameters. Generally, sintering of the nanoparticles is observed. At high laser power densities and/or long irradiation times the average particle/grain size increases reaching values of 200 nm and more. This opens up an opportunity to introduce scattering centers and optimize light trapping within the film, e.g., targeting photovoltaic or photocatalytic applications.