Vanadium-Al_2O_3 nanostructured thin films prepared by pulsed laser deposition: Optical switching

摘要

The formation and optical response of VO_x nanoparticles embedded in amorphous aluminium oxide (Al_2O_3) thin films by pulsed laser deposition is studied. The thin films have been grown by alternate laser ablation of V and Al_2O_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 ℃ and 315 ℃ thus suggesting the presence of nanoparticles with compositions V_4O_7 and V_2O_5, respectively.