Micropatterning of BiVO₄ Thin Films Using Laser-Induced Crystallization

Relatively high temperatures even up to 500 C are required to obtain bismuth vanadate (BiVO₄) films with the scheelite monoclinic (s-m) structure that shows the highest photocatalytic activity. This requirement limits the possible choice of substrates. Moreover, high quality thin layers of crystalline BiVO₄ cannot be prepared with current methods. In this study a light-induced crystallization approach is presented, which is a step toward preparation and patterning of BiVO₄ (s-m) films for applications on plastic substrates. Thin films of amorphous BiVO₄ are prepared by pulsed laser deposition. The possibility of using green (514.7 nm) laser illumination for crystallization of BiVO₄ is investigated. The laser-induced phase transition is tracked using Raman spectroscopy. The results are compared with those obtained from thermally annealed samples, crystalline structure of which is confirmed by measuring X-ray diffraction. The homogeneity and quality of crystallization are verified using micro-Raman spectroscopy imaging, while time-dependent experiments reveal the crystallization rate. The conductivity of the crystallized region is investigated using conductive atomic force microscopy. A strong increase in the conductivity is found in the patterned regions. Experimental results demonstrate the possibility of using the laser-induced crystallization of BiVO₄ to prepare patterns of improved conductivity and semiconducting properties in comparison to amorphous surroundings. The possibility of light-induced crystallization and micropatterning of amorphous bismuth vanadate (BiVO₄) is presented. The photocrystallization process is tracked in situ using Raman spectroscopy. The conducting properties of amorphous and crystalline BiVO₄ are determined using conducting atomic force microscopy. The micropatterned regions exhibit higher conductivity. The photocrystallization process leads to crystallites with scheelite monoclinic structure, which can be applied in photocatalysis.