Laser Direct Writing of Crystallized TiO₂ by Photothermal Effect Induced by Gold Nanoparticles

Near‐infrared (NIR) laser annealing is successfully used to crystallize TiO₂ thin films from a sol–gel solution deposited on gold nanoparticle arrays (AuNPs). The AuNPs are used as nano‐heaters allowing a local temperature increase up to 500 °C in the film. The temperature reached under the laser is deduced from the presence of the anatase phase in the samples obtained by laser exposure, showing that crystallized TiO₂ can be obtained by the photothermal effect. Different analytical techniques supported this study, such as grazing X‐ray diffraction (GIXRD), UV–vis, and Raman spectroscopy. The temperature increase is confirmed by a numerical model that emphasizes the role of NPs coupling in the photothermal effect. Direct laser patterning by NIR laser and in combination with Deep‐UV photolithography (DUV) are demonstrated. This fabrication method opens new perspectives in applications such as photonics, photocatalysis, or biosensing.