Vanadium-Al ₂ O ₃ nanostructured thin films prepared by pulsed laser deposition: Optical switching

The formation and optical response of VO _x nanoparticles embedded in amorphous aluminium oxide (Al ₂ O ₃ ) thin films by pulsed laser deposition is studied. The thin films have been grown by alternate laser ablation of V and Al ₂ O ₃ targets, which has resulted in a multilayer structure with embedded nanoparticles. The V content has been varied by changing the number of pulses on the V target. It is found that VO _x nanoparticles with dimensions around 5 nm have been formed. The structural analysis shows that the vanadium nanoparticles are oxidized, although probably there is not a unique oxide phase for each sample. The films show a different optical response depending on their vanadium content. Optical switching as a function of temperature has been observed for the two films with the highest vanadium content, at transition temperatures of about -20 °C and 315 °C thus suggesting the presence of nanoparticles with compositions V ₄ O ₇ and V ₂ O ₅ , respectively.