Hardness of nanocrystalline TiO2 thin films doped with terbium

In this work influence of terbium dopant on hardness of nanocrystalline TiO₂ thin films have been investigated. Thin films were manufactured by high energy reactive magnetron sputtering process. The structure of TiO₂-matrix was modified by doping with 0.4 at. % of Tb. Undoped matrix had directly after deposition TiO₂-rutile structure with 8.7 nm crystallites in size, while doping with Tb results in anatase structure with 11.7 nm crystallite sizes. Hardness of undoped nanocrystalline matrix was 14.3 GPa, which is two-times higher as-compared to standard TiO₂ coatings. Incorporation of terbium into the matrix results in hardness decrease down to 10.7 GPa, what was directly connected with smaller density of the anatase as-compared to rutile structure.