Effect of the nanocrystalline structure type on the optical properties of TiO2:Nd (1 at.%) thin films

• TiO2:Nd films of anatase and rutile structure were prepared by magnetron sputtering.
• PL and optical properties were discussed in relation to microstructure of thin films.
• Different PL emission efficiencies were found for anatase and rutile thin films.
• More efficient PL emission was obtained for films with rutile phase.
• Stronger PL emission in rutile films might be related to higher refraction index.

Titanium dioxide thin films, each doped with the same amount of neodymium (1 at.%) were deposited by Low Pressure Hot Target Reactive Sputtering and High Energy Reactive Magnetron Sputtering processes in order to obtain anatase and rutile thin film structures respectively. The microstructure and phase composition were analyzed using the transmission electron microscopy method including high resolution electron microscopy imaging. The measurements of the optical properties showed, that both prepared thin films were transparent in the visible light range and had a low extinction coefficient of ca. 3 ⋅ 10−3. The thin film with the anatase structure had a lower cut-off wavelength and refractive index and a higher value of optical energy band gap as-compared to the TiO2:Nd coating with the rutile structure. Simultaneously, more efficient photoluminescence emission was observed for the rutile thin films.