Characterization of nonstoichiometric $TiO2$ and $ZrO2$ thin films stabilized by $Al2O3$ and $SiO2$ additions

Thin films of nonstoichiometric titanium dioxide $(TiO2)$ and zirconium oxide $(ZrO2)$ chemically stabilized by incorporating stoichiometric oxides of $Al2O3$ and $SiO2,$ respectively, were fabricated by rf magnetron sputtering. These films deposited from ceramic targets of $TiO2,$ $TiO2–10 vol %Al2O3,$ $ZrO2,$ and $ZrO2–10 vol %SiO2$ were designated as $TiO2,$ $TiO2–10Al2O3,$ $ZrO2,$ and $ZrO2–10SiO2.$ The dielectric and electrical properties of as-deposited and annealed $TiO2$ and $ZrO2$ films varied with the processing conditions. The addition of $Al2O3$ to $TiO2$ and $SiO2$ to $ZrO2$ films had not only reduced the dielectric loss tangent (tan δ) and increased resistivity, but also retained the competitive dielectric constant (k). The dielectric properties of the $TiO2–10Al2O3$ and $ZrO2–10SiO2$ films became stable under different deposition temperatures and annealing temperatures. The $TiO2–10Al2O3$ films with $k=62,$ tan δ=0.012, resistivity of $2.5×108 Ω cm,$ and breakdown field of 2.2 MV/cm were obtained. $ZrO2–10SiO2$ films with good k values of 20–25 and low tan δ values of 0.011–0.014 can be obtained under rf power of 150 W, while $k=14.5–16.4$ and tan δ=0.012–0.019 under 100 W can be obtained. The advantage of adding the stoichiometric oxides of $Al2O3$ and $SiO2$ is the reduction of oxygen vacancies through the strong affinity of $Al3+$ and $Si4+$ to capture more oxygen for nonstoichiometric oxides of $TiO2$ and $ZrO2.$