Continuous wave ultraviolet-laser sintering of ZnO and TiO2 nanoparticle thin films at low laser powers

In this work, continuous wave UV-laser sintering of ZnO and TiO2 nanoparticle (NP) thin films at different laser powers from 10-80mW focused to a spot size of 10 mu m are studied. We show that laser sintering can be observed even at laser powers as low as 30 mW, using an UV-laser at 325 nm. Compared to these results, laser sintering of ZrO2 nanoparticles is not observed within the laser power range under investigation. Furthermore, we describe the laser heating process numerically using an iterative finite element algorithm, which couples the heat equation with a simplified sintering model. The numerical and experimental results match well and reveal two key parameters responsible for the effective heating and sintering process: The laser wavelength in relation to the wavelength corresponding to the band gap of the material and the initial porosity of the film. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4788906]